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skia2/docs/SkMatrix_Reference.bmh
Brian Salomon fa3783f17d Remove public version of SkMatrix::mapPointsWithStride. 
Use private version already in SkMatrixPriv.

Change-Id: I6e9546afdf2b072402f9deecec99a6d236e2c7f4
Reviewed-on: https://skia-review.googlesource.com/91400
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
2018-01-05 19:32:15 +00:00

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#Topic Matrix
#Alias Matrices
#Alias Matrix_Reference
#Class SkMatrix
Matrix holds a 3x3 matrix for transforming coordinates. This allows mapping
Points and Vectors with translation, scaling, skewing, rotation, and
perspective.
Matrix elements are in row major order. Matrix does not have a constructor,
so it must be explicitly initialized. setIdentity initializes Matrix
so it has no effect. setTranslate, setScale, setSkew, setRotate, set9 and setAll
initializes all Matrix elements with the corresponding mapping.
Matrix includes a hidden variable that classifies the type of matrix to
improve performance. Matrix is not thread safe unless getType is called first.
#Topic Overview
#Subtopic Subtopics
#ToDo manually add subtopics ##
#Table
#Legend
# topics # description ##
#Legend ##
#Table ##
##
#Subtopic Operators
#Table
#Legend
# function # description ##
#Legend ##
# operator!=(const SkMatrix& a, const SkMatrix& b) # Returns true if members are unequal. ##
# operator==(const SkMatrix& a, const SkMatrix& b) # Returns true if members are equal. ##
# operator[](int index)_const # Returns Matrix value. ##
# operator[](int index) # Returns writable reference to Matrix value. ##
#Table ##
#Subtopic ##
#Subtopic Member_Functions
#Table
#Legend
# function # description ##
#Legend ##
# Concat # Returns the concatenation of Matrix pair. ##
# I # Returns a reference to a const identity Matrix. ##
# InvalidMatrix # Returns a reference to a const invalid Matrix. ##
# MakeAll # Constructs all nine values. ##
# MakeRectToRect # Constructs from source Rect to destination Rect. ##
# MakeScale # Constructs from scale in x and y. ##
# MakeTrans # Constructs from translate in x and y. ##
# SetAffineIdentity # Sets 3x2 array to identity. ##
# asAffine # Copies to 3x2 array. ##
# cheapEqualTo # Compares Matrix pair using memcmp(). ##
# decomposeScale # Separates scale if possible. ##
# dirtyMatrixTypeCache # Sets internal cache to unknown state. ##
# dump() # Sends text representation using floats to standard output. ##
# fixedStepInX # Returns step in x for a position in y. ##
# get() # Returns one of nine Matrix values. ##
# get9 # Returns all nine Matrix values. ##
# getMaxScale # Returns maximum scaling, if possible. ##
# getMinMaxScales # Returns minimum and maximum scaling, if possible. ##
# getMinScale # Returns minimum scaling, if possible. ##
# getPerspX # Returns input x perspective factor. ##
# getPerspY # Returns input y perspective factor. ##
# getScaleX # Returns horizontal scale factor. ##
# getScaleY # Returns vertical scale factor. ##
# getSkewX # Returns horizontal skew factor. ##
# getSkewY # Returns vertical skew factor. ##
# getTranslateX # Returns horizontal translation. ##
# getTranslateY # Returns vertical translation. ##
# getType # Returns transform complexity. ##
# hasPerspective # Returns if transform includes perspective. ##
# invert() # Returns inverse, if possible. ##
# isFinite # Returns if all Matrix values are not infinity, NaN. ##
# isFixedStepInX # Returns if transformation supports fixed step in x. ##
# isIdentity # Returns if matrix equals the identity Matrix .##
# isScaleTranslate # Returns if transform is limited to scale and translate. ##
# isSimilarity # Returns if transform is limited to square scale and rotation. ##
# isTranslate # Returns if transform is limited to translate. ##
# mapHomogeneousPoints # Maps Point3 array. ##
# mapPoints # Maps Point array. ##
# mapRadius # Returns mean radius of mapped Circle. ##
# mapRect # Returns bounds of mapped Rect. ##
# mapRectScaleTranslate # Returns bounds of mapped Rect. ##
# mapRectToQuad # Maps Rect to Point array. ##
# mapVector # Maps Vector. ##
# mapVectors # Maps Vector array. ##
# mapXY # Maps Point. ##
# postConcat # Post-multiplies Matrix by Matrix parameter. ##
# postIDiv # Post-multiplies Matrix by inverse scale. ##
# postRotate # Post-multiplies Matrix by rotation. ##
# postScale # Post-multiplies Matrix by scale. ##
# postSkew # Post-multiplies Matrix by skew. ##
# postTranslate # Post-multiplies Matrix by translation. ##
# preConcat # Pre-multiplies Matrix by Matrix parameter.##
# preRotate # Pre-multiplies Matrix by rotation. ##
# preScale # Pre-multiplies Matrix by scale. ##
# preSkew # Pre-multiplies Matrix by skew. ##
# preTranslate # Pre-multiplies Matrix by translation. ##
# preservesAxisAlignment # Returns if mapping restricts to 90 degree multiples and mirroring. ##
# preservesRightAngles # Returns if mapped 90 angle remains 90 degrees. ##
# rectStaysRect # Returns if mapped Rect can be represented by another Rect. ##
# reset() # Sets Matrix to identity. ##
# set() # Sets one value. ##
# set9 # Sets all values from Scalar array. ##
# setAffine # Sets left two columns. ##
# setAll # Sets all values from parameters. ##
# setConcat # Sets to Matrix parameter multiplied by Matrix parameter. ##
# setIdentity # Sets Matrix to identity. ##
# setPerspX # Sets input x perspective factor. ##
# setPerspY # Sets input y perspective factor. ##
# setPolyToPoly # Sets to map one to four points to an equal array of points. ##
# setRSXform # Sets to rotate, scale, and translate. ##
# setRectToRect # Sets to map one Rect to another. ##
# setRotate # Sets to rotate about a point. ##
# setScale # Sets to scale about a point. ##
# setScaleTranslate # Sets to scale and translate. ##
# setScaleX # Sets horizontal scale factor. ##
# setScaleY # Sets vertical scale factor ##
# setSinCos # Sets to rotate and scale about a point. ##
# setSkew # Sets to skew about a point. ##
# setSkewX # Sets horizontal skew factor. ##
# setSkewY # Sets vertical skew factor. ##
# setTranslate # Sets to translate in x and y. ##
# setTranslateX # Sets horizontal translation. ##
# setTranslateY # Sets vertical translation. ##
# toString # Converts Matrix to machine readable form. ##
#Table ##
#Subtopic ##
#Topic ##
# ------------------------------------------------------------------------------
#Method static SkMatrix SK_WARN_UNUSED_RESULT MakeScale(SkScalar sx, SkScalar sy)
Sets Matrix to scale by (sx, sy). Returned matrix is:
#Code
#Literal
| sx 0 0 |
| 0 sy 0 |
| 0 0 1 |
##
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Return Matrix with scale ##
#Example
#Image 4
canvas->concat(SkMatrix::MakeScale(4, 3));
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso setScale postScale preScale
##
# ------------------------------------------------------------------------------
#Method static SkMatrix SK_WARN_UNUSED_RESULT MakeScale(SkScalar scale)
Sets Matrix to scale by (scale, scale). Returned matrix is:
#Code
#Literal
| scale 0 0 |
| 0 scale 0 |
| 0 0 1 |
##
#Param scale horizontal and vertical scale factor ##
#Return Matrix with scale ##
#Example
#Image 4
canvas->concat(SkMatrix::MakeScale(4));
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso setScale postScale preScale
##
# ------------------------------------------------------------------------------
#Method static SkMatrix SK_WARN_UNUSED_RESULT MakeTrans(SkScalar dx, SkScalar dy)
Sets Matrix to translate by (dx, dy). Returned matrix is:
#Code
#Literal
| 1 0 dx |
| 0 1 dy |
| 0 0 1 |
##
#Param dx horizontal translation ##
#Param dy vertical translation ##
#Return Matrix with translation ##
#Example
#Image 4
SkMatrix matrix = SkMatrix::MakeTrans(64, 48);
for (int i = 0; i < 4; ++i) {
canvas->drawBitmap(source, 0, 0);
canvas->concat(matrix);
}
##
#SeeAlso setTranslate postTranslate preTranslate
##
# ------------------------------------------------------------------------------
#Method static SkMatrix SK_WARN_UNUSED_RESULT MakeAll(SkScalar scaleX, SkScalar skewX, SkScalar transX,
SkScalar skewY, SkScalar scaleY, SkScalar transY,
SkScalar pers0, SkScalar pers1, SkScalar pers2)
Sets Matrix to:
#Code
#Literal
| scaleX skewX transX |
| skewY scaleY transY |
| pers0 pers1 pers2 |
##
#Param scaleX horizontal scale factor ##
#Param skewX horizontal skew factor ##
#Param transX horizontal translation ##
#Param skewY vertical skew factor ##
#Param scaleY vertical scale factor ##
#Param transY vertical translation ##
#Param pers0 input x perspective factor ##
#Param pers1 input y perspective factor ##
#Param pers2 perspective scale factor ##
#Return Matrix constructed from parameters ##
#Example
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(64);
for (SkScalar sx : { -1, 1 } ) {
for (SkScalar sy : { -1, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
SkMatrix m = SkMatrix::MakeAll(sx, 1, 128, 0, sy, 128, 0, 0, 1);
canvas->concat(m);
canvas->drawString("K", 0, 0, p);
}
}
##
#SeeAlso setAll set9 postConcat preConcat
##
# ------------------------------------------------------------------------------
#Enum TypeMask
#Code
enum TypeMask {
kIdentity_Mask = 0,
kTranslate_Mask = 0x01,
kScale_Mask = 0x02,
kAffine_Mask = 0x04,
kPerspective_Mask = 0x08,
};
##
Enum of bit fields for mask returned by getType.
Used to identify the complexity of Matrix, to optimize performance.
#Const kIdentity_Mask 0
all bits clear if Matrix is identity
##
#Const kTranslate_Mask 1
set if Matrix has translation
##
#Const kScale_Mask 2
set if Matrix has x or y scale
##
#Const kAffine_Mask 4
set if Matrix skews or rotates
##
#Const kPerspective_Mask 8
set if Matrix has perspective
##
#Example
auto debugster = [](const char* prefix, const SkMatrix& matrix) -> void {
SkString typeMask;
typeMask += SkMatrix::kIdentity_Mask == matrix.getType() ? "kIdentity_Mask " : "";
typeMask += SkMatrix::kTranslate_Mask & matrix.getType() ? "kTranslate_Mask " : "";
typeMask += SkMatrix::kScale_Mask & matrix.getType() ? "kScale_Mask " : "";
typeMask += SkMatrix::kAffine_Mask & matrix.getType() ? "kAffine_Mask " : "";
typeMask += SkMatrix::kPerspective_Mask & matrix.getType() ? "kPerspective_Mask" : "";
SkDebugf("after %s: %s\n", prefix, typeMask.c_str());
};
SkMatrix matrix;
matrix.reset();
debugster("reset", matrix);
matrix.postTranslate(1, 0);
debugster("postTranslate", matrix);
matrix.postScale(2, 1);
debugster("postScale", matrix);
matrix.postRotate(45);
debugster("postScale", matrix);
SkPoint polys[][4] = {{{0, 0}, {0, 1}, {1, 1}, {1, 0}}, {{0, 0}, {0, 1}, {2, 1}, {1, 0}}};
matrix.setPolyToPoly(polys[0], polys[1], 4);
debugster("setPolyToPoly", matrix);
#StdOut
after reset: kIdentity_Mask
after postTranslate: kTranslate_Mask
after postScale: kTranslate_Mask kScale_Mask
after postScale: kTranslate_Mask kScale_Mask kAffine_Mask
after setPolyToPoly: kTranslate_Mask kScale_Mask kAffine_Mask kPerspective_Mask
##
##
#SeeAlso getType
##
# ------------------------------------------------------------------------------
#Method TypeMask getType() const
Returns a bit field describing the transformations the matrix may
perform. The bit field is computed conservatively, so it may include
false positives. For example, when kPerspective_Mask is set, all
other bits are set.
#Return kIdentity_Mask, or combinations of: kTranslate_Mask, kScale_Mask,
kAffine_Mask, kPerspective_Mask
##
#Example
SkMatrix matrix;
matrix.setAll(1, 0, 0, 0, 1, 0, 0, 0, 1);
SkDebugf("identity flags hex: %0x decimal: %d\n", matrix.getType(), matrix.getType());
matrix.setAll(1, 0, 0, 0, 1, 0, 0, 0, .5f);
SkDebugf("set all flags hex: %0x decimal: %d\n", matrix.getType(), matrix.getType());
#StdOut
identity flags hex: 0 decimal: 0
set all flags hex: f decimal: 15
##
##
#SeeAlso TypeMask
##
# ------------------------------------------------------------------------------
#Method bool isIdentity() const
Returns true if Matrix is identity. Identity matrix is:
#Code
#Literal
| 1 0 0 |
| 0 1 0 |
| 0 0 1 |
##
#Return true if Matrix has no effect ##
#Example
SkMatrix matrix;
matrix.setAll(1, 0, 0, 0, 1, 0, 0, 0, 1);
SkDebugf("is identity: %s\n", matrix.isIdentity() ? "true" : "false");
matrix.setAll(1, 0, 0, 0, 1, 0, 0, 0, 2);
SkDebugf("is identity: %s\n", matrix.isIdentity() ? "true" : "false");
#StdOut
is identity: true
is identity: false
##
##
#SeeAlso reset() setIdentity getType
##
# ------------------------------------------------------------------------------
#Method bool isScaleTranslate() const
Returns true if Matrix at most scales and translates. Matrix may be identity,
contain only scale elements, only translate elements, or both. Matrix form is:
#Code
#Literal
| scale-x 0 translate-x |
| 0 scale-y translate-y |
| 0 0 1 |
##
#Return true if Matrix is identity; or scales, translates, or both ##
#Example
SkMatrix matrix;
for (SkScalar scaleX : { 1, 2 } ) {
for (SkScalar translateX : { 0, 20 } ) {
matrix.setAll(scaleX, 0, translateX, 0, 1, 0, 0, 0, 1);
SkDebugf("is scale-translate: %s\n", matrix.isScaleTranslate() ? "true" : "false");
}
}
#StdOut
is scale-translate: true
is scale-translate: true
is scale-translate: true
is scale-translate: true
##
##
#SeeAlso setScale isTranslate setTranslate getType
##
# ------------------------------------------------------------------------------
#Method bool isTranslate() const
Returns true if Matrix is identity, or translates. Matrix form is:
#Code
#Literal
| 1 0 translate-x |
| 0 1 translate-y |
| 0 0 1 |
##
#Return true if Matrix is identity, or translates ##
#Example
SkMatrix matrix;
for (SkScalar scaleX : { 1, 2 } ) {
for (SkScalar translateX : { 0, 20 } ) {
matrix.setAll(scaleX, 0, translateX, 0, 1, 0, 0, 0, 1);
SkDebugf("is translate: %s\n", matrix.isTranslate() ? "true" : "false");
}
}
#StdOut
is translate: true
is translate: true
is translate: false
is translate: false
##
##
#SeeAlso setTranslate getType
##
# ------------------------------------------------------------------------------
#Method bool rectStaysRect() const
Returns true Matrix maps Rect to another Rect. If true, Matrix is identity,
or scales, or rotates a multiple of 90 degrees, or mirrors in x or y. In all
cases, Matrix may also have translation. Matrix form is either:
#Code
#Literal
| scale-x 0 translate-x |
| 0 scale-y translate-y |
| 0 0 1 |
##
or
#Code
#Literal
| 0 rotate-x translate-x |
| rotate-y 0 translate-y |
| 0 0 1 |
##
for non-zero values of scale-x, scale-y, rotate-x, and rotate-y.
Also called preservesAxisAlignment; use the one that provides better inline
documentation.
#Return true if Matrix maps one Rect into another ##
#Example
SkMatrix matrix;
for (SkScalar angle: { 0, 90, 180, 270 } ) {
matrix.setRotate(angle);
SkDebugf("rectStaysRect: %s\n", matrix.rectStaysRect() ? "true" : "false");
}
#StdOut
rectStaysRect: true
rectStaysRect: true
rectStaysRect: true
rectStaysRect: true
##
##
#SeeAlso preservesAxisAlignment preservesRightAngles
##
# ------------------------------------------------------------------------------
#Method bool preservesAxisAlignment() const
Returns true Matrix maps Rect to another Rect. If true, Matrix is identity,
or scales, or rotates a multiple of 90 degrees, or mirrors in x or y. In all
cases, Matrix may also have translation. Matrix form is either:
#Code
#Literal
| scale-x 0 translate-x |
| 0 scale-y translate-y |
| 0 0 1 |
##
or
#Code
#Literal
| 0 rotate-x translate-x |
| rotate-y 0 translate-y |
| 0 0 1 |
##
for non-zero values of scale-x, scale-y, rotate-x, and rotate-y.
Also called rectStaysRect; use the one that provides better inline
documentation.
#Return true if Matrix maps one Rect into another ##
#Example
SkMatrix matrix;
for (SkScalar angle: { 0, 90, 180, 270 } ) {
matrix.setRotate(angle);
SkDebugf("preservesAxisAlignment: %s\n", matrix.preservesAxisAlignment() ? "true" : "false");
}
#StdOut
preservesAxisAlignment: true
preservesAxisAlignment: true
preservesAxisAlignment: true
preservesAxisAlignment: true
##
##
#SeeAlso rectStaysRect preservesRightAngles
##
# ------------------------------------------------------------------------------
#Method bool hasPerspective() const
Returns true if the matrix contains perspective elements. Matrix form is:
#Code
#Literal
| -- -- -- |
| -- -- -- |
| perspective-x perspective-y perspective-scale |
##
where perspective-x or perspective-y is non-zero, or perspective-scale is
not one. All other elements may have any value.
#Return true if Matrix is in most general form ##
#Example
#Image 4
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
canvas->concat(matrix);
SkString string;
string.printf("hasPerspective %s", matrix.hasPerspective() ? "true" : "false");
canvas->drawBitmap(source, 0, 0);
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(48);
canvas->drawString(string, 0, source.bounds().height() + 48, paint);
##
#SeeAlso setAll set9 MakeAll
##
# ------------------------------------------------------------------------------
#Method bool isSimilarity(SkScalar tol = SK_ScalarNearlyZero) const
Returns true if Matrix contains only translation, rotation, reflection, and
uniform scale.
Returns false if Matrix contains different scales, skewing, perspective, or
degenerate forms that collapse to a line or point.
Describes that the Matrix makes rendering with and without the matrix are
visually alike; a transformed circle remains a circle. Mathematically, this is
referred to as similarity of a Euclidean_Space, or a similarity transformation.
Preserves right angles, keeping the arms of the angle equal lengths.
#Param tol to be deprecated ##
#Return true if Matrix only rotates, uniformly scales, translates ##
#Example
#Description
String is drawn four times through but only two are visible. Drawing the pair
with isSimilarity false reveals the pair not visible through the matrix.
##
SkPaint p;
p.setAntiAlias(true);
SkMatrix m;
int below = 175;
for (SkScalar sx : { -1, 1 } ) {
for (SkScalar sy : { -1, 1 } ) {
m.setAll(sx, 1, 128, 1, sy, 32, 0, 0, 1);
bool isSimilarity = m.isSimilarity();
SkString str;
str.printf("sx: %g sy: %g sim: %s", sx, sy, isSimilarity ? "true" : "false");
{
SkAutoCanvasRestore autoRestore(canvas, true);
canvas->concat(m);
canvas->drawString(str, 0, 0, p);
}
if (!isSimilarity) {
canvas->drawString(str, 40, below, p);
below += 20;
}
}
}
##
#SeeAlso isScaleTranslate preservesRightAngles rectStaysRect isFixedStepInX
##
# ------------------------------------------------------------------------------
#Method bool preservesRightAngles(SkScalar tol = SK_ScalarNearlyZero) const
Returns true if Matrix contains only translation, rotation, reflection, and
scale. Scale may differ along rotated axes.
Returns false if Matrix skewing, perspective, or degenerate forms that collapse
to a line or point.
Preserves right angles, but not requiring that the arms of the angle
retain equal lengths.
#Param tol to be deprecated ##
#Return true if Matrix only rotates, scales, translates ##
#Example
#Height 128
#Description
Equal scale is both similar and preserves right angles.
Unequal scale is not similar but preserves right angles.
Skews are not similar and do not preserve right angles.
##
SkPaint p;
p.setAntiAlias(true);
SkMatrix m;
int pos = 0;
for (SkScalar sx : { 1, 2 } ) {
for (SkScalar kx : { 0, 1 } ) {
m.setAll(sx, kx, 16, 0, 1, 32, 0, 0, 1);
bool isSimilarity = m.isSimilarity();
bool preservesRightAngles = m.preservesRightAngles();
SkString str;
str.printf("sx: %g kx: %g %s %s", sx, kx, isSimilarity ? "sim" : "",
preservesRightAngles ? "right" : "");
SkAutoCanvasRestore autoRestore(canvas, true);
canvas->concat(m);
canvas->drawString(str, 0, pos, p);
pos += 20;
}
}
##
#SeeAlso isScaleTranslate isSimilarity rectStaysRect isFixedStepInX
##
# ------------------------------------------------------------------------------
#Enum
#Code
enum {
kMScaleX,
kMSkewX,
kMTransX,
kMSkewY,
kMScaleY,
kMTransY,
kMPersp0,
kMPersp1,
kMPersp2,
};
##
Matrix organizes its values in row order. These members correspond to
each value in Matrix.
#Const kMScaleX 0
horizontal scale factor
##
#Const kMSkewX 1
horizontal skew factor
##
#Const kMTransX 2
horizontal translation
##
#Const kMSkewY 3
vertical skew factor
##
#Const kMScaleY 4
vertical scale factor
##
#Const kMTransY 5
vertical translation
##
#Const kMPersp0 6
input x perspective factor
##
#Const kMPersp1 7
input y perspective factor
##
#Const kMPersp2 8
perspective bias
##
#Example
SkPaint black;
black.setAntiAlias(true);
black.setTextSize(48);
SkPaint gray = black;
gray.setColor(0xFF9f9f9f);
SkScalar offset[] = { 1.5f, 1.5f, 20, 1.5f, 1.5f, 20, .03f, .01f, 2 };
for (int i : { SkMatrix::kMScaleX, SkMatrix::kMSkewX, SkMatrix::kMTransX,
SkMatrix::kMSkewY, SkMatrix::kMScaleY, SkMatrix::kMTransY,
SkMatrix::kMPersp0, SkMatrix::kMPersp1, SkMatrix::kMPersp2 } ) {
SkMatrix m;
m.setIdentity();
m.set(i, offset[i]);
SkAutoCanvasRestore autoRestore(canvas, true);
canvas->translate(22 + (i % 3) * 88, 44 + (i / 3) * 88);
canvas->drawString("&", 0, 0, gray);
canvas->concat(m);
canvas->drawString("&", 0, 0, black);
}
##
#SeeAlso get() set()
##
# ------------------------------------------------------------------------------
#Enum
#Code
enum {
kAScaleX,
kASkewY,
kASkewX,
kAScaleY,
kATransX,
kATransY,
};
##
Affine arrays are in column major order to match the matrix used by
PDF and XPS.
#Const kAScaleX 0
horizontal scale factor
##
#Const kASkewY 1
vertical skew factor
##
#Const kASkewX 2
horizontal skew factor
##
#Const kAScaleY 3
vertical scale factor
##
#Const kATransX 4
horizontal translation
##
#Const kATransY 5
vertical translation
##
#NoExample
##
#SeeAlso SetAffineIdentity asAffine setAffine
##
# ------------------------------------------------------------------------------
#Method SkScalar operator[](int index)_const
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is
defined.
#Param index one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY,
kMPersp0, kMPersp1, kMPersp2
##
#Return value corresponding to index ##
#Example
SkMatrix matrix;
matrix.setScale(42, 24);
SkDebugf("matrix[SkMatrix::kMScaleX] %c= 42\n", matrix[SkMatrix::kMScaleX] == 42 ? '=' : '!');
SkDebugf("matrix[SkMatrix::kMScaleY] %c= 24\n", matrix[SkMatrix::kMScaleY] == 24 ? '=' : '!');
#StdOut
matrix[SkMatrix::kMScaleX] == 42
matrix[SkMatrix::kMScaleY] == 24
##
##
#SeeAlso get set
##
# ------------------------------------------------------------------------------
#Method SkScalar get(int index) const
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is
defined.
#Param index one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY,
kMPersp0, kMPersp1, kMPersp2
##
#Return value corresponding to index ##
#Example
SkMatrix matrix;
matrix.setSkew(42, 24);
SkDebugf("matrix.get(SkMatrix::kMSkewX) %c= 42\n",
matrix.get(SkMatrix::kMSkewX) == 42 ? '=' : '!');
SkDebugf("matrix.get(SkMatrix::kMSkewY) %c= 24\n",
matrix.get(SkMatrix::kMSkewY) == 24 ? '=' : '!');
#StdOut
matrix.get(SkMatrix::kMSkewX) == 42
matrix.get(SkMatrix::kMSkewY) == 24
##
##
#SeeAlso operator[](int index) set
##
# ------------------------------------------------------------------------------
#Method SkScalar getScaleX() const
Returns scale factor multiplied by x input, contributing to x output.
With mapPoints, scales Points along the x-axis.
#Return horizontal scale factor ##
#Example
SkMatrix matrix;
matrix.setScale(42, 24);
SkDebugf("matrix.getScaleX() %c= 42\n", matrix.getScaleX() == 42 ? '=' : '!');
#StdOut
matrix.getScaleX() == 42
##
##
#SeeAlso get getScaleY setScaleX setScale
##
# ------------------------------------------------------------------------------
#Method SkScalar getScaleY() const
Returns scale factor multiplied by y input, contributing to y output.
With mapPoints, scales Points along the y-axis.
#Return vertical scale factor ##
#Example
SkMatrix matrix;
matrix.setScale(42, 24);
SkDebugf("matrix.getScaleY() %c= 24\n", matrix.getScaleY() == 24 ? '=' : '!');
#StdOut
matrix.getScaleY() == 24
##
##
#SeeAlso get getScaleX setScaleY setScale
##
# ------------------------------------------------------------------------------
#Method SkScalar getSkewY() const
Returns scale factor multiplied by x input, contributing to y output.
With mapPoints, skews Points along the y-axis.
Skew x and y together can rotate Points.
#Return vertical skew factor ##
#Example
SkMatrix matrix;
matrix.setSkew(42, 24);
SkDebugf("matrix.getSkewY() %c= 24\n", matrix.getSkewY() == 24 ? '=' : '!');
#StdOut
matrix.getSkewY() == 24
##
##
#SeeAlso get getSkewX setSkewY setSkew
##
# ------------------------------------------------------------------------------
#Method SkScalar getSkewX() const
Returns scale factor multiplied by y input, contributing to x output.
With mapPoints, skews Points along the x-axis.
Skew x and y together can rotate Points.
#Return horizontal scale factor ##
#Example
SkMatrix matrix;
matrix.setSkew(42, 24);
SkDebugf("matrix.getSkewX() %c= 42\n", matrix.getSkewX() == 42 ? '=' : '!');
#StdOut
matrix.getSkewX() == 42
##
##
#SeeAlso get getSkewY setSkewX setSkew
##
# ------------------------------------------------------------------------------
#Method SkScalar getTranslateX() const
Returns translation contributing to x output.
With mapPoints, moves Points along the x-axis.
#Return horizontal translation factor ##
#Example
SkMatrix matrix;
matrix.setTranslate(42, 24);
SkDebugf("matrix.getTranslateX() %c= 42\n", matrix.getTranslateX() == 42 ? '=' : '!');
#StdOut
matrix.getTranslateX() == 42
##
##
#SeeAlso get getTranslateY setTranslateX setTranslate
##
# ------------------------------------------------------------------------------
#Method SkScalar getTranslateY() const
Returns translation contributing to y output.
With mapPoints, moves Points along the y-axis.
#Return vertical translation factor ##
#Example
SkMatrix matrix;
matrix.setTranslate(42, 24);
SkDebugf("matrix.getTranslateY() %c= 24\n", matrix.getTranslateY() == 24 ? '=' : '!');
#StdOut
matrix.getTranslateY() == 24
##
##
#SeeAlso get getTranslateX setTranslateY setTranslate
##
# ------------------------------------------------------------------------------
#Method SkScalar getPerspX() const
Returns factor scaling input x relative to input y.
#Return input x perspective factor ##
#Example
SkMatrix m;
m.setIdentity();
m.set(SkMatrix::kMPersp0, -0.004f);
SkAutoCanvasRestore autoRestore(canvas, true);
canvas->translate(22, 144);
SkPaint black;
black.setAntiAlias(true);
black.setTextSize(24);
SkPaint gray = black;
gray.setColor(0xFF9f9f9f);
SkString string;
string.appendScalar(m.getPerspX());
canvas->drawString(string, 0, -72, gray);
canvas->concat(m);
canvas->drawString(string, 0, 0, black);
##
#SeeAlso kMPersp0 getPerspY
##
# ------------------------------------------------------------------------------
#Method SkScalar getPerspY() const
Returns factor scaling input y relative to input x.
#Return input y perspective factor ##
#Example
SkMatrix m;
m.setIdentity();
m.set(SkMatrix::kMPersp1, -0.004f);
SkAutoCanvasRestore autoRestore(canvas, true);
canvas->translate(22, 144);
SkPaint black;
black.setAntiAlias(true);
black.setTextSize(24);
SkPaint gray = black;
gray.setColor(0xFF9f9f9f);
SkString string;
string.appendScalar(m.getPerspY());
canvas->drawString(string, 0, -72, gray);
canvas->concat(m);
canvas->drawString(string, 0, 0, black);
##
#SeeAlso kMPersp1 getPerspX
##
# ------------------------------------------------------------------------------
#Method SkScalar& operator[](int index)
Returns writable Matrix value. Asserts if index is out of range and SK_DEBUG is
defined. Clears internal cache anticipating that caller will change Matrix value.
Next call to read Matrix state may recompute cache; subsequent writes to Matrix
value must be followed by dirtyMatrixTypeCache.
#Param index one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY,
kMPersp0, kMPersp1, kMPersp2
##
#Return writable value corresponding to index ##
#Example
SkMatrix matrix;
matrix.setIdentity();
SkDebugf("with identity matrix: x = %g\n", matrix.mapXY(24, 42).fX);
SkScalar& skewRef = matrix[SkMatrix::kMSkewX];
skewRef = 0;
SkDebugf("after skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
skewRef = 1;
SkDebugf("after 2nd skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
matrix.dirtyMatrixTypeCache();
SkDebugf("after dirty cache: x = %g\n", matrix.mapXY(24, 42).fX);
#StdOut
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 24
after dirty cache: x = 66
##
##
#SeeAlso get dirtyMatrixTypeCache set
##
# ------------------------------------------------------------------------------
#Method void set(int index, SkScalar value)
Sets Matrix value. Asserts if index is out of range and SK_DEBUG is
defined. Safer than operator[]; internal cache is always maintained.
#Param index one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY,
kMPersp0, kMPersp1, kMPersp2
##
#Param value Scalar to store in Matrix ##
#Example
SkMatrix matrix;
matrix.setIdentity();
SkDebugf("with identity matrix: x = %g\n", matrix.mapXY(24, 42).fX);
matrix.set(SkMatrix::kMSkewX, 0);
SkDebugf("after skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
matrix.set(SkMatrix::kMSkewX, 1);
SkDebugf("after 2nd skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
#StdOut
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 66
##
##
#SeeAlso operator[] get
#Method ##
# ------------------------------------------------------------------------------
#Method void setScaleX(SkScalar v)
Sets horizontal scale factor.
#Param v horizontal scale factor to store ##
#Example
#Height 64
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 12, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setScaleX(3);
canvas->concat(matrix);
canvas->drawString("x scale", 0, 48, paint);
##
#SeeAlso set setScale setScaleY
#Method ##
# ------------------------------------------------------------------------------
#Method void setScaleY(SkScalar v)
Sets vertical scale factor.
#Param v vertical scale factor to store ##
#Example
#Height 192
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 12, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setScaleY(3);
canvas->concat(matrix);
canvas->drawString("y scale", 12, 48, paint);
##
#SeeAlso set setScale setScaleX
#Method ##
# ------------------------------------------------------------------------------
#Method void setSkewY(SkScalar v)
Sets vertical skew factor.
#Param v vertical skew factor to store ##
#Example
#Height 96
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 12, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setSkewY(.3f);
canvas->concat(matrix);
canvas->drawString("y skew", 12, 48, paint);
##
#SeeAlso set setSkew setSkewX
#Method ##
# ------------------------------------------------------------------------------
#Method void setSkewX(SkScalar v)
Sets horizontal skew factor.
#Param v horizontal skew factor to store ##
#Example
#Height 64
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 12, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setSkewX(-.7f);
canvas->concat(matrix);
canvas->drawString("x skew", 36, 48, paint);
##
#SeeAlso set setSkew setSkewX
#Method ##
# ------------------------------------------------------------------------------
#Method void setTranslateX(SkScalar v)
Sets horizontal translation.
#Param v horizontal translation to store ##
#Example
#Height 48
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 8, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setTranslateX(96);
canvas->concat(matrix);
canvas->drawString("x translate", 8, 24, paint);
##
#SeeAlso set setTranslate setTranslateY
#Method ##
# ------------------------------------------------------------------------------
#Method void setTranslateY(SkScalar v)
Sets vertical translation.
#Param v vertical translation to store ##
#Example
#Height 64
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 8, 24, paint);
SkMatrix matrix;
matrix.setIdentity();
matrix.setTranslateY(24);
canvas->concat(matrix);
canvas->drawString("y translate", 8, 24, paint);
##
#SeeAlso set setTranslate setTranslateX
#Method ##
# ------------------------------------------------------------------------------
#Method void setPerspX(SkScalar v)
Sets input x perspective factor, which causes mapXY to vary input x inversely
proportional to input y.
#Param v perspective factor ##
#Example
#Image 4
for (SkScalar perspX : { -.003f, 0.f, .003f, .012f } ) {
SkMatrix matrix;
matrix.setIdentity();
matrix.setPerspX(perspX);
canvas->save();
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
canvas->restore();
canvas->translate(64, 64);
}
##
#SeeAlso getPerspX set setAll set9 MakeAll
#Method ##
# ------------------------------------------------------------------------------
#Method void setPerspY(SkScalar v)
Sets input y perspective factor, which causes mapXY to vary input y inversely
proportional to input x.
#Param v perspective factor ##
#Example
#Image 4
for (SkScalar perspX : { -.003f, 0.f, .003f, .012f } ) {
SkMatrix matrix;
matrix.setIdentity();
matrix.setPerspY(perspX);
canvas->save();
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
canvas->restore();
canvas->translate(64, 64);
}
##
#SeeAlso getPerspY set setAll set9 MakeAll
#Method ##
# ------------------------------------------------------------------------------
#Method void setAll(SkScalar scaleX, SkScalar skewX, SkScalar transX,
SkScalar skewY, SkScalar scaleY, SkScalar transY,
SkScalar persp0, SkScalar persp1, SkScalar persp2)
Sets all values from parameters. Sets matrix to:
#Code
#Literal
| scaleX skewX transX |
| skewY scaleY transY |
| persp0 persp1 persp2 |
##
#Param scaleX horizontal scale factor to store ##
#Param skewX horizontal skew factor to store ##
#Param transX horizontal translation to store ##
#Param skewY vertical skew factor to store ##
#Param scaleY vertical scale factor to store ##
#Param transY vertical translation to store ##
#Param persp0 input x perspective factor to store ##
#Param persp1 input y perspective factor to store ##
#Param persp2 perspective scale factor to store ##
#Example
#Height 128
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(64);
SkMatrix m;
for (SkScalar sx : { -1, 1 } ) {
for (SkScalar sy : { -1, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
m.setAll(sx, 1, 128, 0, sy, 64, 0, 0, 1);
canvas->concat(m);
canvas->drawString("K", 0, 0, p);
}
}
##
#SeeAlso set9 MakeAll
#Method ##
# ------------------------------------------------------------------------------
#Method void get9(SkScalar buffer[9]) const
Copies nine Scalar values contained by Matrix into buffer, in member value
ascending order: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY,
kMPersp0, kMPersp1, kMPersp2.
#Param buffer storage for nine Scalar values ##
#Example
SkMatrix matrix = SkMatrix::MakeRectToRect({0, 0, 1, 1}, {3, 4, 7, 9},
SkMatrix::kFill_ScaleToFit);
SkScalar b[9];
matrix.get9(b);
SkDebugf("{%g, %g, %g},\n{%g, %g, %g},\n{%g, %g, %g}\n", b[0], b[1], b[2],
b[3], b[4], b[5], b[6], b[7], b[8]);
#StdOut
{4, 0, 3},
{0, 5, 4},
{0, 0, 1}
##
##
#SeeAlso set9
#Method ##
# ------------------------------------------------------------------------------
#Method void set9(const SkScalar buffer[9])
Sets Matrix to nine Scalar values in buffer, in member value ascending order:
kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1,
kMPersp2.
Sets matrix to:
#Code
#Literal
| buffer[0] buffer[1] buffer[2] |
| buffer[3] buffer[4] buffer[5] |
| buffer[6] buffer[7] buffer[8] |
##
In the future, set9 followed by get9 may not return the same values. Since Matrix
maps non-homogeneous coordinates, scaling all nine values produces an equivalent
transformation, possibly improving precision.
#Param buffer nine Scalar values ##
#Example
#Image 4
SkMatrix m;
SkScalar buffer[9] = {4, 0, 3, 0, 5, 4, 0, 0, 1};
m.set9(buffer);
canvas->concat(m);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso setAll get9 MakeAll
#Method ##
# ------------------------------------------------------------------------------
#Method void reset()
Sets Matrix to identity; which has no effect on mapped Points. Sets Matrix to:
#Code
#Literal
| 1 0 0 |
| 0 1 0 |
| 0 0 1 |
##
Also called setIdentity(); use the one that provides better inline
documentation.
#Example
SkMatrix m;
m.reset();
SkDebugf("m.isIdentity(): %s\n", m.isIdentity() ? "true" : "false");
#StdOut
m.isIdentity(): true
##
##
#SeeAlso isIdentity setIdentity
#Method ##
# ------------------------------------------------------------------------------
#Method void setIdentity()
Sets Matrix to identity; which has no effect on mapped Points. Sets Matrix to:
#Code
#Literal
| 1 0 0 |
| 0 1 0 |
| 0 0 1 |
##
Also called reset(); use the one that provides better inline
documentation.
#Example
SkMatrix m;
m.setIdentity();
SkDebugf("m.isIdentity(): %s\n", m.isIdentity() ? "true" : "false");
#StdOut
m.isIdentity(): true
##
##
#SeeAlso isIdentity reset
#Method ##
# ------------------------------------------------------------------------------
#Method void setTranslate(SkScalar dx, SkScalar dy)
Sets Matrix to translate by (dx, dy).
#Param dx horizontal translation ##
#Param dy vertical translation ##
#Example
#Height 64
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 8, 24, paint);
SkMatrix matrix;
matrix.setTranslate(96, 24);
canvas->concat(matrix);
canvas->drawString("translate", 8, 24, paint);
##
#SeeAlso setTranslateX setTranslateY
#Method ##
# ------------------------------------------------------------------------------
#Method void setTranslate(const SkVector& v)
Sets Matrix to translate by (v.fX, v.fY).
#Param v Vector containing horizontal and vertical translation ##
#Example
#Height 64
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
canvas->drawString("normal", 8, 24, paint);
SkMatrix matrix;
matrix.setTranslate({96, 24});
canvas->concat(matrix);
canvas->drawString("translate", 8, 24, paint);
##
#SeeAlso setTranslateX setTranslateY MakeTrans
#Method ##
# ------------------------------------------------------------------------------
#Method void setScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets Matrix to scale by sx and sy, about a pivot point at (px, py).
The pivot point is unchanged when mapped with Matrix.
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Height 128
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(64);
SkMatrix m;
for (SkScalar sx : { -1, 1 } ) {
for (SkScalar sy : { -1, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
m.setScale(sx, sy, 128, 64);
canvas->concat(m);
canvas->drawString("%", 128, 64, p);
}
}
##
#SeeAlso setScaleX setScaleY MakeScale preScale postScale
#Method ##
# ------------------------------------------------------------------------------
#Method void setScale(SkScalar sx, SkScalar sy)
Sets Matrix to scale by sx and sy about at pivot point at (0, 0).
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Example
#Height 128
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(64);
SkMatrix m;
for (SkScalar sx : { -1, 1 } ) {
for (SkScalar sy : { -1, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
m.setScale(sx, sy);
m.postTranslate(128, 64);
canvas->concat(m);
canvas->drawString("@", 0, 0, p);
}
}
##
#SeeAlso setScaleX setScaleY MakeScale preScale postScale
#Method ##
# ------------------------------------------------------------------------------
#Method void setRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets Matrix to rotate by degrees about a pivot point at (px, py).
The pivot point is unchanged when mapped with Matrix.
Positive degrees rotates clockwise.
#Param degrees angle of axes relative to upright axes ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Height 128
SkPaint paint;
paint.setColor(SK_ColorGRAY);
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
SkMatrix matrix;
matrix.setRotate(25, rect.centerX(), rect.centerY());
canvas->concat(matrix);
canvas->drawRect(rect, paint);
##
#SeeAlso setSinCos preRotate postRotate
#Method ##
# ------------------------------------------------------------------------------
#Method void setRotate(SkScalar degrees)
Sets Matrix to rotate by degrees about a pivot point at (0, 0).
Positive degrees rotates clockwise.
#Param degrees angle of axes relative to upright axes ##
#Example
#Height 128
SkPaint paint;
paint.setColor(SK_ColorGRAY);
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
SkMatrix matrix;
matrix.setRotate(25);
canvas->translate(rect.centerX(), rect.centerY());
canvas->concat(matrix);
canvas->translate(-rect.centerX(), -rect.centerY());
canvas->drawRect(rect, paint);
##
#SeeAlso setSinCos preRotate postRotate
#Method ##
# ------------------------------------------------------------------------------
#Method void setSinCos(SkScalar sinValue, SkScalar cosValue,
SkScalar px, SkScalar py)
Sets Matrix to rotate by sinValue and cosValue, about a pivot point at (px, py).
The pivot point is unchanged when mapped with Matrix.
Vector (sinValue, cosValue) describes the angle of rotation relative to (0, 1).
Vector length specifies scale.
#Param sinValue rotation vector x component ##
#Param cosValue rotation vector y component ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Height 128
SkPaint paint;
paint.setColor(SK_ColorGRAY);
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
SkMatrix matrix;
matrix.setSinCos(.25f, .85f, rect.centerX(), rect.centerY());
canvas->concat(matrix);
canvas->drawRect(rect, paint);
##
#SeeAlso setRotate setScale setRSXform
#Method ##
# ------------------------------------------------------------------------------
#Method void setSinCos(SkScalar sinValue, SkScalar cosValue)
Sets Matrix to rotate by sinValue and cosValue, about a pivot point at (0, 0).
Vector (sinValue, cosValue) describes the angle of rotation relative to (0, 1).
Vector length specifies scale.
#Param sinValue rotation vector x component ##
#Param cosValue rotation vector y component ##
#Example
#Description
Canvas needs offset after applying Matrix to pivot about Rect center.
##
#Height 128
SkPaint paint;
paint.setColor(SK_ColorGRAY);
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
SkMatrix matrix;
matrix.setSinCos(.25f, .85f);
matrix.postTranslate(rect.centerX(), rect.centerY());
canvas->concat(matrix);
canvas->translate(-rect.centerX(), -rect.centerY());
canvas->drawRect(rect, paint);
##
#SeeAlso setRotate setScale setRSXform
#Method ##
# ------------------------------------------------------------------------------
#Method SkMatrix& setRSXform(const SkRSXform& rsxForm)
Sets Matrix to rotate, scale, and translate using a compressed matrix form.
Vector (rsxForm.fSSin, rsxForm.fSCos) describes the angle of rotation relative
to (0, 1). Vector length specifies scale. Mapped point is rotated and scaled
by Vector, then translated by (rsxForm.fTx, rsxForm.fTy).
#Param rsxForm compressed RSXform matrix ##
#Return reference to Matrix ##
#Example
#Description
Canvas needs offset after applying Matrix to pivot about Rect center.
##
#Height 128
SkPaint paint;
paint.setColor(SK_ColorGRAY);
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
SkMatrix matrix;
matrix.setRSXform(SkRSXform::Make(.85f, .25f, rect.centerX(), rect.centerY()));
canvas->concat(matrix);
canvas->translate(-rect.centerX(), -rect.centerY());
canvas->drawRect(rect, paint);
##
#SeeAlso setSinCos setScale setTranslate
#Method ##
# ------------------------------------------------------------------------------
#Method void setSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets Matrix to skew by kx and ky, about a pivot point at (px, py).
The pivot point is unchanged when mapped with Matrix.
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(48);
SkMatrix m;
for (SkScalar sx : { -1, 0, 1 } ) {
for (SkScalar sy : { -1, 0, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
m.setSkew(sx, sy, 96 + 64 * sx, 128 + 48 * sy);
canvas->concat(m);
canvas->drawString("K", 96 + 64 * sx, 128 + 48 * sy, p);
}
}
##
#SeeAlso setSkewX setSkewY preSkew postSkew
#Method ##
# ------------------------------------------------------------------------------
#Method void setSkew(SkScalar kx, SkScalar ky)
Sets Matrix to skew by kx and ky, about a pivot point at (0, 0).
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Example
SkPaint p;
p.setAntiAlias(true);
p.setTextSize(48);
SkMatrix m;
for (SkScalar sx : { -1, 0, 1 } ) {
for (SkScalar sy : { -1, 0, 1 } ) {
SkAutoCanvasRestore autoRestore(canvas, true);
m.setSkew(sx, sy);
m.postTranslate(96 + 64 * sx, 128 + 48 * sy);
canvas->concat(m);
canvas->drawString("K", 0, 0, p);
}
}
##
#SeeAlso setSkewX setSkewY preSkew postSkew
#Method ##
# ------------------------------------------------------------------------------
#Method void setConcat(const SkMatrix& a, const SkMatrix& b)
Sets Matrix to Matrix a multiplied by Matrix b. Either a or b may be this.
Given:
#Code
#Literal
| A B C | | J K L |
a = | D E F |, b = | M N O |
| G H I | | P Q R |
##
sets Matrix to:
#Code
#Literal
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR |
a * b = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR |
| G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
##
#Param a Matrix on left side of multiply expression ##
#Param b Matrix on right side of multiply expression ##
#Example
#Image 3
#Description
setPolyToPoly creates perspective matrices, one the inverse of the other.
Multiplying the matrix by its inverse turns into an identity matrix.
##
SkMatrix matrix, matrix2;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix2.setPolyToPoly(perspect, bitmapBounds, 4);
matrix.setConcat(matrix, matrix2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso Concat preConcat postConcat SkCanvas::concat
#Method ##
# ------------------------------------------------------------------------------
#Method void preTranslate(SkScalar dx, SkScalar dy)
Sets Matrix to Matrix multiplied by Matrix constructed from translation (dx, dy).
This can be thought of as moving the point to be mapped before applying Matrix.
Given:
#Code
#Literal
| A B C | | 1 0 dx |
Matrix = | D E F |, T(dx, dy) = | 0 1 dy |
| G H I | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| A B C | | 1 0 dx | | A B A*dx+B*dy+C |
Matrix * T(dx, dy) = | D E F | | 0 1 dy | = | D E D*dx+E*dy+F |
| G H I | | 0 0 1 | | G H G*dx+H*dy+I |
##
#Param dx x translation before applying Matrix ##
#Param dy y translation before applying Matrix ##
#Example
#Height 160
SkPaint paint;
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
for (int i = 0; i < 2; ++i ) {
SkMatrix matrix;
i == 0 ? matrix.reset(): matrix.setRotate(25, rect.centerX(), 320);
{
SkAutoCanvasRestore acr(canvas, true);
canvas->concat(matrix);
paint.setColor(SK_ColorGRAY);
canvas->drawRect(rect, paint);
}
paint.setColor(SK_ColorRED);
for (int j = 0; j < 2; ++j ) {
SkAutoCanvasRestore acr(canvas, true);
matrix.preTranslate(40, 40);
canvas->concat(matrix);
canvas->drawCircle(0, 0, 3, paint);
}
}
##
#SeeAlso postTranslate setTranslate MakeTrans
#Method ##
# ------------------------------------------------------------------------------
#Method void preScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets Matrix to Matrix multiplied by Matrix constructed from scaling by (sx, sy)
about pivot point (px, py).
This can be thought of as scaling about a pivot point before applying Matrix.
Given:
#Code
#Literal
| A B C | | sx 0 dx |
Matrix = | D E F |, S(sx, sy, px, py) = | 0 sy dy |
| G H I | | 0 0 1 |
##
where
#Code
#Literal
dx = px - sx * px
dy = py - sy * py
##
sets Matrix to:
#Code
#Literal
| A B C | | sx 0 dx | | A*sx B*sy A*dx+B*dy+C |
Matrix * S(sx, sy, px, py) = | D E F | | 0 sy dy | = | D*sx E*sy D*dx+E*dy+F |
| G H I | | 0 0 1 | | G*sx H*sy G*dx+H*dy+I |
##
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preScale(.75f, 1.5f, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postScale setScale MakeScale
#Method ##
# ------------------------------------------------------------------------------
#Method void preScale(SkScalar sx, SkScalar sy)
Sets Matrix to Matrix multiplied by Matrix constructed from scaling by (sx, sy)
about pivot point (0, 0).
This can be thought of as scaling about the origin before applying Matrix.
Given:
#Code
#Literal
| A B C | | sx 0 0 |
Matrix = | D E F |, S(sx, sy) = | 0 sy 0 |
| G H I | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| A B C | | sx 0 0 | | A*sx B*sy C |
Matrix * S(sx, sy) = | D E F | | 0 sy 0 | = | D*sx E*sy F |
| G H I | | 0 0 1 | | G*sx H*sy I |
##
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preScale(.75f, 1.5f);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postScale setScale MakeScale
#Method ##
# ------------------------------------------------------------------------------
#Method void preRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets Matrix to Matrix multiplied by Matrix constructed from rotating by degrees
about pivot point (px, py).
This can be thought of as rotating about a pivot point before applying Matrix.
Positive degrees rotates clockwise.
Given:
#Code
#Literal
| A B C | | c -s dx |
Matrix = | D E F |, R(degrees, px, py) = | s c dy |
| G H I | | 0 0 1 |
##
where
#Code
#Literal
c = cos(degrees)
s = sin(degrees)
dx = s * py + (1 - c) * px
dy = -s * px + (1 - c) * py
##
sets Matrix to:
#Code
#Literal
| A B C | | c -s dx | | Ac+Bs -As+Bc A*dx+B*dy+C |
Matrix * R(degrees, px, py) = | D E F | | s c dy | = | Dc+Es -Ds+Ec D*dx+E*dy+F |
| G H I | | 0 0 1 | | Gc+Hs -Gs+Hc G*dx+H*dy+I |
##
#Param degrees angle of axes relative to upright axes ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preRotate(45, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postRotate setRotate
#Method ##
# ------------------------------------------------------------------------------
#Method void preRotate(SkScalar degrees)
Sets Matrix to Matrix multiplied by Matrix constructed from rotating by degrees
about pivot point (0, 0).
This can be thought of as rotating about the origin before applying Matrix.
Positive degrees rotates clockwise.
Given:
#Code
#Literal
| A B C | | c -s 0 |
Matrix = | D E F |, R(degrees, px, py) = | s c 0 |
| G H I | | 0 0 1 |
##
where
#Code
#Literal
c = cos(degrees)
s = sin(degrees)
##
sets Matrix to:
#Code
#Literal
| A B C | | c -s 0 | | Ac+Bs -As+Bc C |
Matrix * R(degrees, px, py) = | D E F | | s c 0 | = | Dc+Es -Ds+Ec F |
| G H I | | 0 0 1 | | Gc+Hs -Gs+Hc I |
##
#Param degrees angle of axes relative to upright axes ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preRotate(45);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postRotate setRotate
#Method ##
# ------------------------------------------------------------------------------
#Method void preSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets Matrix to Matrix multiplied by Matrix constructed from skewing by (kx, ky)
about pivot point (px, py).
This can be thought of as skewing about a pivot point before applying Matrix.
Given:
#Code
#Literal
| A B C | | 1 kx dx |
Matrix = | D E F |, K(kx, ky, px, py) = | ky 1 dy |
| G H I | | 0 0 1 |
##
where
#Code
#Literal
dx = -kx * py
dy = -ky * px
##
sets Matrix to:
#Code
#Literal
| A B C | | 1 kx dx | | A+B*ky A*kx+B A*dx+B*dy+C |
Matrix * K(kx, ky, px, py) = | D E F | | ky 1 dy | = | D+E*ky D*kx+E D*dx+E*dy+F |
| G H I | | 0 0 1 | | G+H*ky G*kx+H G*dx+H*dy+I |
##
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preSkew(.5f, 0, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postSkew setSkew
#Method ##
# ------------------------------------------------------------------------------
#Method void preSkew(SkScalar kx, SkScalar ky)
Sets Matrix to Matrix multiplied by Matrix constructed from skewing by (kx, ky)
about pivot point (0, 0).
This can be thought of as skewing about the origin before applying Matrix.
Given:
#Code
#Literal
| A B C | | 1 kx 0 |
Matrix = | D E F |, K(kx, ky) = | ky 1 0 |
| G H I | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| A B C | | 1 kx 0 | | A+B*ky A*kx+B C |
Matrix * K(kx, ky) = | D E F | | ky 1 0 | = | D+E*ky D*kx+E F |
| G H I | | 0 0 1 | | G+H*ky G*kx+H I |
##
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.preSkew(.5f, 0);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postSkew setSkew
#Method ##
# ------------------------------------------------------------------------------
#Method void preConcat(const SkMatrix& other)
Sets Matrix to Matrix multiplied by Matrix other.
This can be thought of mapping by other before applying Matrix.
Given:
#Code
#Literal
| A B C | | J K L |
Matrix = | D E F |, other = | M N O |
| G H I | | P Q R |
##
sets Matrix to:
#Code
#Literal
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR |
Matrix * other = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR |
| G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
##
#Param other Matrix on right side of multiply expression ##
#Example
#Image 3
#Description
setPolyToPoly creates perspective matrices, one the inverse of the other.
Multiplying the matrix by its inverse turns into an identity matrix.
##
SkMatrix matrix, matrix2;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix2.setPolyToPoly(perspect, bitmapBounds, 4);
matrix.preConcat(matrix2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postConcat setConcat Concat
#Method ##
# ------------------------------------------------------------------------------
#Method void postTranslate(SkScalar dx, SkScalar dy)
Sets Matrix to Matrix constructed from translation (dx, dy) multiplied by Matrix.
This can be thought of as moving the point to be mapped after applying Matrix.
Given:
#Code
#Literal
| J K L | | 1 0 dx |
Matrix = | M N O |, T(dx, dy) = | 0 1 dy |
| P Q R | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| 1 0 dx | | J K L | | J+dx*P K+dx*Q L+dx*R |
T(dx, dy) * Matrix = | 0 1 dy | | M N O | = | M+dy*P N+dy*Q O+dy*R |
| 0 0 1 | | P Q R | | P Q R |
##
#Param dx x translation after applying Matrix ##
#Param dy y translation after applying Matrix ##
#Example
#Height 160
#Description
Compare with preTranslate example.
##
SkPaint paint;
paint.setAntiAlias(true);
SkRect rect = {20, 20, 100, 100};
for (int i = 0; i < 2; ++i ) {
SkMatrix matrix;
i == 0 ? matrix.reset(): matrix.setRotate(25, rect.centerX(), 320);
{
SkAutoCanvasRestore acr(canvas, true);
canvas->concat(matrix);
paint.setColor(SK_ColorGRAY);
canvas->drawRect(rect, paint);
}
paint.setColor(SK_ColorRED);
for (int j = 0; j < 2; ++j ) {
SkAutoCanvasRestore acr(canvas, true);
matrix.postTranslate(40, 40);
canvas->concat(matrix);
canvas->drawCircle(0, 0, 3, paint);
}
}
##
#SeeAlso preTranslate setTranslate MakeTrans
#Method ##
# ------------------------------------------------------------------------------
#Method void postScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py)
Sets Matrix to Matrix constructed from scaling by (sx, sy) about pivot point
(px, py), multiplied by Matrix.
This can be thought of as scaling about a pivot point after applying Matrix.
Given:
#Code
#Literal
| J K L | | sx 0 dx |
Matrix = | M N O |, S(sx, sy, px, py) = | 0 sy dy |
| P Q R | | 0 0 1 |
##
where
#Code
#Literal
dx = px - sx * px
dy = py - sy * py
##
sets Matrix to:
#Code
#Literal
| sx 0 dx | | J K L | | sx*J+dx*P sx*K+dx*Q sx*L+dx+R |
S(sx, sy, px, py) * Matrix = | 0 sy dy | | M N O | = | sy*M+dy*P sy*N+dy*Q sy*O+dy*R |
| 0 0 1 | | P Q R | | P Q R |
##
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postScale(.75f, 1.5f, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preScale setScale MakeScale
##
# ------------------------------------------------------------------------------
#Method void postScale(SkScalar sx, SkScalar sy)
Sets Matrix to Matrix constructed from scaling by (sx, sy) about pivot point
(0, 0), multiplied by Matrix.
This can be thought of as scaling about the origin after applying Matrix.
Given:
#Code
#Literal
| J K L | | sx 0 0 |
Matrix = | M N O |, S(sx, sy) = | 0 sy 0 |
| P Q R | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| sx 0 0 | | J K L | | sx*J sx*K sx*L |
S(sx, sy) * Matrix = | 0 sy 0 | | M N O | = | sy*M sy*N sy*O |
| 0 0 1 | | P Q R | | P Q R |
##
#Param sx horizontal scale factor ##
#Param sy vertical scale factor ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postScale(.75f, 1.5f);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preScale setScale MakeScale
##
# ------------------------------------------------------------------------------
#Method bool postIDiv(int divx, int divy)
Sets Matrix to Matrix constructed from scaling by
#Formula
(1/divx, 1/divy)
##
about pivot point (px, py), multiplied by Matrix.
Returns false if either divx or divy is zero.
Given:
#Code
#Literal
| J K L | | sx 0 0 |
Matrix = | M N O |, I(divx, divy) = | 0 sy 0 |
| P Q R | | 0 0 1 |
##
where
#Code
#Literal
sx = 1 / divx
sy = 1 / divy
##
sets Matrix to:
#Code
#Literal
| sx 0 0 | | J K L | | sx*J sx*K sx*L |
I(divx, divy) * Matrix = | 0 sy 0 | | M N O | = | sy*M sy*N sy*O |
| 0 0 1 | | P Q R | | P Q R |
##
#Param divx integer divisor for inverse scale in x ##
#Param divy integer divisor for inverse scale in y ##
#Return true on successful scale ##
#Example
#Image 3
SkMatrix matrix, matrix2;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postIDiv(1, 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso postScale MakeScale
##
# ------------------------------------------------------------------------------
#Method void postRotate(SkScalar degrees, SkScalar px, SkScalar py)
Sets Matrix to Matrix constructed from rotating by degrees about pivot point
(px, py), multiplied by Matrix.
This can be thought of as rotating about a pivot point after applying Matrix.
Positive degrees rotates clockwise.
Given:
#Code
#Literal
| J K L | | c -s dx |
Matrix = | M N O |, R(degrees, px, py) = | s c dy |
| P Q R | | 0 0 1 |
##
where
#Code
#Literal
c = cos(degrees)
s = sin(degrees)
dx = s * py + (1 - c) * px
dy = -s * px + (1 - c) * py
##
sets Matrix to:
#Code
#Literal
|c -s dx| |J K L| |cJ-sM+dx*P cK-sN+dx*Q cL-sO+dx+R|
R(degrees, px, py) * Matrix = |s c dy| |M N O| = |sJ+cM+dy*P sK+cN+dy*Q sL+cO+dy*R|
|0 0 1| |P Q R| | P Q R|
##
#Param degrees angle of axes relative to upright axes ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postRotate(45, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preRotate setRotate
##
# ------------------------------------------------------------------------------
#Method void postRotate(SkScalar degrees)
Sets Matrix to Matrix constructed from rotating by degrees about pivot point
(0, 0), multiplied by Matrix.
This can be thought of as rotating about the origin after applying Matrix.
Positive degrees rotates clockwise.
Given:
#Code
#Literal
| J K L | | c -s 0 |
Matrix = | M N O |, R(degrees, px, py) = | s c 0 |
| P Q R | | 0 0 1 |
##
where
#Code
#Literal
c = cos(degrees)
s = sin(degrees)
##
sets Matrix to:
#Code
#Literal
| c -s dx | | J K L | | cJ-sM cK-sN cL-sO |
R(degrees, px, py) * Matrix = | s c dy | | M N O | = | sJ+cM sK+cN sL+cO |
| 0 0 1 | | P Q R | | P Q R |
##
#Param degrees angle of axes relative to upright axes ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postRotate(45);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preRotate setRotate
##
# ------------------------------------------------------------------------------
#Method void postSkew(SkScalar kx, SkScalar ky, SkScalar px, SkScalar py)
Sets Matrix to Matrix constructed from skewing by (kx, ky) about pivot point
(px, py), multiplied by Matrix.
This can be thought of as skewing about a pivot point after applying Matrix.
Given:
#Code
#Literal
| J K L | | 1 kx dx |
Matrix = | M N O |, K(kx, ky, px, py) = | ky 1 dy |
| P Q R | | 0 0 1 |
##
where
#Code
#Literal
dx = -kx * py
dy = -ky * px
##
sets Matrix to:
#Code
#Literal
| 1 kx dx| |J K L| |J+kx*M+dx*P K+kx*N+dx*Q L+kx*O+dx+R|
K(kx, ky, px, py) * Matrix = |ky 1 dy| |M N O| = |ky*J+M+dy*P ky*K+N+dy*Q ky*L+O+dy*R|
| 0 0 1| |P Q R| | P Q R|
##
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Param px pivot x ##
#Param py pivot y ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postSkew(.5f, 0, source.width() / 2, source.height() / 2);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preSkew setSkew
##
# ------------------------------------------------------------------------------
#Method void postSkew(SkScalar kx, SkScalar ky)
Sets Matrix to Matrix constructed from skewing by (kx, ky) about pivot point
(0, 0), multiplied by Matrix.
This can be thought of as skewing about the origin after applying Matrix.
Given:
#Code
#Literal
| J K L | | 1 kx 0 |
Matrix = | M N O |, K(kx, ky) = | ky 1 0 |
| P Q R | | 0 0 1 |
##
sets Matrix to:
#Code
#Literal
| 1 kx 0 | | J K L | | J+kx*M K+kx*N L+kx*O |
K(kx, ky) * Matrix = | ky 1 0 | | M N O | = | ky*J+M ky*K+N ky*L+O |
| 0 0 1 | | P Q R | | P Q R |
##
#Param kx horizontal skew factor ##
#Param ky vertical skew factor ##
#Example
#Image 3
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postSkew(.5f, 0);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preSkew setSkew
##
# ------------------------------------------------------------------------------
#Method void postConcat(const SkMatrix& other)
Sets Matrix to Matrix other multiplied by Matrix.
This can be thought of mapping by other after applying Matrix.
Given:
#Code
#Literal
| J K L | | A B C |
Matrix = | M N O |, other = | D E F |
| P Q R | | G H I |
##
sets Matrix to:
#Code
#Literal
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR |
other * Matrix = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR |
| G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
##
#Param other Matrix on left side of multiply expression ##
#Example
#Image 3
#Height 64
SkMatrix matrix, matrix2;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix.postConcat(matrix);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preConcat setConcat Concat
##
# ------------------------------------------------------------------------------
#Enum ScaleToFit
#Code
enum ScaleToFit {
kFill_ScaleToFit,
kStart_ScaleToFit,
kCenter_ScaleToFit,
kEnd_ScaleToFit,
};
##
ScaleToFit describes how Matrix is constructed to map one Rect to another.
ScaleToFit may allow Matrix to have unequal horizontal and vertical scaling,
or may restrict Matrix to square scaling. If restricted, ScaleToFit specifies
how Matrix maps to the side or center of the destination Rect.
#Const kFill_ScaleToFit 0
Computes Matrix that scales in x and y independently, so that source Rect is
mapped to completely fill destination Rect. The aspect ratio of source Rect
may change.
##
#Const kStart_ScaleToFit 1
Computes Matrix that maintains source Rect aspect ratio, mapping source Rect
width or height to destination Rect. Aligns mapping to left and top edges
of destination Rect.
##
#Const kCenter_ScaleToFit 2
Computes Matrix that maintains source Rect aspect ratio, mapping source Rect
width or height to destination Rect. Aligns mapping to center of destination
Rect.
##
#Const kEnd_ScaleToFit 3
Computes Matrix that maintains source Rect aspect ratio, mapping source Rect
width or height to destination Rect. Aligns mapping to right and bottom
edges of destination Rect.
##
#Example
const char* labels[] = { "Fill", "Start", "Center", "End" };
SkRect rects[] = {{5, 5, 59, 59}, {5, 74, 59, 108}, {10, 123, 44, 172}, {10, 187, 54, 231}};
SkRect bounds;
source.getBounds(&bounds);
SkPaint paint;
paint.setAntiAlias(true);
for (auto fit : { SkMatrix::kFill_ScaleToFit, SkMatrix::kStart_ScaleToFit,
SkMatrix::kCenter_ScaleToFit, SkMatrix::kEnd_ScaleToFit } ) {
for (auto rect : rects ) {
canvas->drawRect(rect, paint);
SkMatrix matrix;
if (!matrix.setRectToRect(bounds, rect, fit)) {
continue;
}
SkAutoCanvasRestore acr(canvas, true);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
}
canvas->drawString(labels[fit], 10, 255, paint);
canvas->translate(64, 0);
}
##
#SeeAlso setRectToRect MakeRectToRect setPolyToPoly
##
# ------------------------------------------------------------------------------
#Method bool setRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf)
Sets Matrix to scale and translate src Rect to dst Rect. stf selects whether
mapping completely fills dst or preserves the aspect ratio, and how to align
src within dst. Returns false if src is empty, and sets Matrix to identity.
Returns true if dst is empty, and sets Matrix to:
#Code
#Literal
| 0 0 0 |
| 0 0 0 |
| 0 0 1 |
##
#Param src Rect to map from ##
#Param dst Rect to map to ##
#Param stf one of: kFill_ScaleToFit, kStart_ScaleToFit,
kCenter_ScaleToFit, kEnd_ScaleToFit
##
#Return true if Matrix can represent Rect mapping ##
#Example
const SkRect srcs[] = { {0, 0, 0, 0}, {1, 2, 3, 4} };
const SkRect dsts[] = { {0, 0, 0, 0}, {5, 6, 8, 9} };
for (auto src : srcs) {
for (auto dst : dsts) {
SkMatrix matrix;
matrix.setAll(-1, -1, -1, -1, -1, -1, -1, -1, -1);
bool success = matrix.setRectToRect(src, dst, SkMatrix::kFill_ScaleToFit);
SkDebugf("src: %g, %g, %g, %g dst: %g, %g, %g, %g success: %s\n",
src.fLeft, src.fTop, src.fRight, src.fBottom,
dst.fLeft, dst.fTop, dst.fRight, dst.fBottom, success ? "true" : "false");
matrix.dump();
}
}
#StdOut
src: 0, 0, 0, 0 dst: 0, 0, 0, 0 success: false
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 0, 0, 0, 0 dst: 5, 6, 8, 9 success: false
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 1, 2, 3, 4 dst: 0, 0, 0, 0 success: true
[ 0.0000 0.0000 0.0000][ 0.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 1, 2, 3, 4 dst: 5, 6, 8, 9 success: true
[ 1.5000 0.0000 3.5000][ 0.0000 1.5000 3.0000][ 0.0000 0.0000 1.0000]
##
##
#SeeAlso MakeRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
##
# ------------------------------------------------------------------------------
#Method static SkMatrix MakeRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit stf)
Returns Matrix set to scale and translate src Rect to dst Rect. stf selects
whether mapping completely fills dst or preserves the aspect ratio, and how to
align src within dst. Returns the identity Matrix if src is empty. If dst is
empty, returns Matrix set to:
#Code
#Literal
| 0 0 0 |
| 0 0 0 |
| 0 0 1 |
##
#Param src Rect to map from ##
#Param dst Rect to map to ##
#Param stf one of: kFill_ScaleToFit, kStart_ScaleToFit,
kCenter_ScaleToFit, kEnd_ScaleToFit
##
#Return Matrix mapping src to dst ##
#Example
const SkRect srcs[] = { {0, 0, 0, 0}, {1, 2, 3, 4} };
const SkRect dsts[] = { {0, 0, 0, 0}, {5, 6, 8, 9} };
for (auto src : srcs) {
for (auto dst : dsts) {
SkMatrix matrix = SkMatrix::MakeRectToRect(src, dst, SkMatrix::kFill_ScaleToFit);
SkDebugf("src: %g, %g, %g, %g dst: %g, %g, %g, %g\n",
src.fLeft, src.fTop, src.fRight, src.fBottom,
dst.fLeft, dst.fTop, dst.fRight, dst.fBottom);
matrix.dump();
}
}
#StdOut
src: 0, 0, 0, 0 dst: 0, 0, 0, 0
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 0, 0, 0, 0 dst: 5, 6, 8, 9
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 1, 2, 3, 4 dst: 0, 0, 0, 0
[ 0.0000 0.0000 0.0000][ 0.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
src: 1, 2, 3, 4 dst: 5, 6, 8, 9
[ 1.5000 0.0000 3.5000][ 0.0000 1.5000 3.0000][ 0.0000 0.0000 1.0000]
##
##
#SeeAlso setRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
##
# ------------------------------------------------------------------------------
#Method bool setPolyToPoly(const SkPoint src[], const SkPoint dst[], int count)
Sets Matrix to map src to dst. count must be zero or greater, and four or less.
If count is zero, sets Matrix to identity and returns true.
If count is one, sets Matrix to translate and returns true.
If count is two or more, sets Matrix to map Points if possible; returns false
if Matrix cannot be constructed. If count is four, Matrix may include
perspective.
#Param src Points to map from ##
#Param dst Points to map to ##
#Param count number of Points in src and dst ##
#Return true if Matrix was constructed successfully
##
#Example
const SkPoint src[] = { { 0, 0}, {30, 0}, {30, -30}, { 0, -30} };
const SkPoint dst[] = { {50, 0}, {80, -10}, {90, -30}, {60, -40} };
SkPaint blackPaint;
blackPaint.setAntiAlias(true);
blackPaint.setTextSize(42);
SkPaint redPaint = blackPaint;
redPaint.setColor(SK_ColorRED);
for (int count : { 1, 2, 3, 4 } ) {
canvas->translate(35, 55);
for (int index = 0; index < count; ++index) {
canvas->drawCircle(src[index], 3, blackPaint);
canvas->drawCircle(dst[index], 3, blackPaint);
if (index > 0) {
canvas->drawLine(src[index], src[index - 1], blackPaint);
canvas->drawLine(dst[index], dst[index - 1], blackPaint);
}
}
SkMatrix matrix;
matrix.setPolyToPoly(src, dst, count);
canvas->drawString("A", src[0].fX, src[0].fY, redPaint);
SkAutoCanvasRestore acr(canvas, true);
canvas->concat(matrix);
canvas->drawString("A", src[0].fX, src[0].fY, redPaint);
}
##
#SeeAlso setRectToRect MakeRectToRect
##
# ------------------------------------------------------------------------------
#Method bool SK_WARN_UNUSED_RESULT invert(SkMatrix* inverse) const
Sets inverse to reciprocal matrix, returning true if Matrix can be inverted.
Geometrically, if Matrix maps from source to destination, inverse Matrix
maps from destination to source. If Matrix can not be inverted, inverse is
unchanged.
#Param inverse storage for inverted Matrix; may be nullptr ##
#Return true if Matrix can be inverted ##
#Example
#Height 128
const SkPoint src[] = { { 10, 120}, {120, 120}, {120, 10}, { 10, 10} };
const SkPoint dst[] = { {150, 120}, {200, 100}, {240, 30}, { 130, 40} };
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
matrix.setPolyToPoly(src, dst, 4);
canvas->drawPoints(SkCanvas::kPolygon_PointMode, 4, src, paint);
canvas->drawPoints(SkCanvas::kPolygon_PointMode, 4, dst, paint);
paint.setColor(SK_ColorBLUE);
paint.setStrokeWidth(3);
paint.setStrokeCap(SkPaint::kRound_Cap);
canvas->drawPoints(SkCanvas::kPoints_PointMode, 4, dst, paint);
matrix.invert(&matrix);
canvas->concat(matrix);
canvas->drawPoints(SkCanvas::kPoints_PointMode, 4, dst, paint);
##
#SeeAlso Concat
##
# ------------------------------------------------------------------------------
#Method static void SetAffineIdentity(SkScalar affine[6])
Fills affine with identity values in column major order.
Sets affine to:
#Code
#Literal
| 1 0 0 |
| 0 1 0 |
##
Affine 3x2 matrices in column major order are used by OpenGL and XPS.
#Param affine storage for 3x2 affine matrix ##
#Example
SkScalar affine[6];
SkMatrix::SetAffineIdentity(affine);
const char* names[] = { "ScaleX", "SkewY", "SkewX", "ScaleY", "TransX", "TransY" };
for (int i = 0; i < 6; ++i) {
SkDebugf("%s: %g ", names[i], affine[i]);
}
SkDebugf("\n");
#StdOut
ScaleX: 1 SkewY: 0 SkewX: 0 ScaleY: 1 TransX: 0 TransY: 0
##
##
#SeeAlso setAffine asAffine
##
# ------------------------------------------------------------------------------
#Method bool SK_WARN_UNUSED_RESULT asAffine(SkScalar affine[6]) const
Fills affine in column major order. Sets affine to:
#Code
#Literal
| scale-x skew-x translate-x |
| skew-y scale-y translate-y |
##
If Matrix contains perspective, returns false and leaves affine unchanged.
#Param affine storage for 3x2 affine matrix; may be nullptr ##
#Return true if Matrix does not contain perspective ##
#Example
SkMatrix matrix;
matrix.setAll(2, 3, 4, 5, 6, 7, 0, 0, 1);
SkScalar affine[6];
matrix.asAffine(affine);
const char* names[] = { "ScaleX", "SkewY", "SkewX", "ScaleY", "TransX", "TransY" };
for (int i = 0; i < 6; ++i) {
SkDebugf("%s: %g ", names[i], affine[i]);
}
SkDebugf("\n");
#StdOut
ScaleX: 2 SkewY: 5 SkewX: 3 ScaleY: 6 TransX: 4 TransY: 7
##
##
#SeeAlso setAffine SetAffineIdentity
##
# ------------------------------------------------------------------------------
#Method void setAffine(const SkScalar affine[6])
Sets Matrix to affine values, passed in column major order. Given affine,
column, then row, as:
#Code
#Literal
| scale-x skew-x translate-x |
| skew-y scale-y translate-y |
##
Matrix is set, row, then column, to:
#Code
#Literal
| scale-x skew-x translate-x |
| skew-y scale-y translate-y |
| 0 0 1 |
##
#Param affine 3x2 affine matrix ##
#Example
SkMatrix matrix;
matrix.setAll(2, 3, 4, 5, 6, 7, 0, 0, 1);
SkScalar affine[6];
matrix.asAffine(affine);
const char* names[] = { "ScaleX", "SkewY", "SkewX", "ScaleY", "TransX", "TransY" };
for (int i = 0; i < 6; ++i) {
SkDebugf("%s: %g ", names[i], affine[i]);
}
SkDebugf("\n");
matrix.reset();
matrix.setAffine(affine);
matrix.dump();
#StdOut
ScaleX: 2 SkewY: 5 SkewX: 3 ScaleY: 6 TransX: 4 TransY: 7
[ 2.0000 3.0000 4.0000][ 5.0000 6.0000 7.0000][ 0.0000 0.0000 1.0000]
##
##
#SeeAlso asAffine SetAffineIdentity
##
# ------------------------------------------------------------------------------
#Method void mapPoints(SkPoint dst[], const SkPoint src[], int count) const
Maps src Point array of length count to dst Point array of equal or greater
length. Points are mapped by multiplying each Point by Matrix. Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
##
where
#Code
#Literal
for (i = 0; i < count; ++i) {
x = src[i].fX
y = src[i].fY
}
##
each dst Point is computed as:
#Code
#Literal
|A B C| |x| Ax+By+C Dx+Ey+F
Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
src and dst may point to the same storage.
#Param dst storage for mapped Points ##
#Param src Points to transform ##
#Param count number of Points to transform ##
#Example
SkMatrix matrix;
matrix.reset();
const int count = 4;
SkPoint src[count];
matrix.mapRectToQuad(src, {40, 70, 180, 220} );
SkPaint paint;
paint.setARGB(77, 23, 99, 154);
for (int i = 0; i < 5; ++i) {
SkPoint dst[count];
matrix.mapPoints(dst, src, count);
canvas->drawPoints(SkCanvas::kPolygon_PointMode, count, dst, paint);
matrix.preRotate(35, 128, 128);
}
##
#SeeAlso mapXY mapHomogeneousPoints mapVectors
##
# ------------------------------------------------------------------------------
#Method void mapPoints(SkPoint pts[], int count) const
Maps pts Point array of length count in place. Points are mapped by multiplying
each Point by Matrix. Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
##
where
#Code
#Literal
for (i = 0; i < count; ++i) {
x = pts[i].fX
y = pts[i].fY
}
##
each resulting pts Point is computed as:
#Code
#Literal
|A B C| |x| Ax+By+C Dx+Ey+F
Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
#Param pts storage for mapped Points ##
#Param count number of Points to transform ##
#Example
SkMatrix matrix;
matrix.setRotate(35, 128, 128);
const int count = 4;
SkPoint pts[count];
matrix.mapRectToQuad(pts, {40, 70, 180, 220} );
SkPaint paint;
paint.setARGB(77, 23, 99, 154);
for (int i = 0; i < 5; ++i) {
canvas->drawPoints(SkCanvas::kPolygon_PointMode, count, pts, paint);
matrix.mapPoints(pts, count);
}
##
#SeeAlso mapXY mapHomogeneousPoints mapVectors
##
# ------------------------------------------------------------------------------
#Method void mapHomogeneousPoints(SkPoint3 dst[], const SkPoint3 src[], int count) const
Maps src Point3 array of length count to dst Point3 array, which must of length count or
greater. Point3 array is mapped by multiplying each Point3 by Matrix. Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, src = | y |
| G H I | | z |
##
each resulting dst Point is computed as:
#Code
#Literal
|A B C| |x|
Matrix * src = |D E F| |y| = |Ax+By+Cz Dx+Ey+Fz Gx+Hy+Iz|
|G H I| |z|
##
#Param dst storage for mapped Point3 array ##
#Param src Point3 array to transform ##
#Param count items in Point3 array to transform ##
#Example
SkPoint3 src[] = {{3, 3, 1}, {8, 2, 2}, {5, 0, 4}, {0, 1, 3},
{3, 7, 1}, {8, 6, 2}, {5, 4, 4}, {0, 5, 3}};
int lines[] = { 0, 1, 1, 2, 2, 3, 3, 0, 4, 5, 5, 6, 6, 7, 7, 4, 0, 4, 1, 5, 2, 6, 3, 7 };
constexpr int count = SK_ARRAY_COUNT(src);
auto debugster = [=](SkPoint3 src[]) -> void {
for (size_t i = 0; i < SK_ARRAY_COUNT(lines); i += 2) {
const SkPoint3& s = src[lines[i]];
const SkPoint3& e = src[lines[i + 1]];
SkPaint paint;
paint.setARGB(77, 23, 99, 154);
canvas->drawLine(s.fX / s.fZ, s.fY / s.fZ, e.fX / e.fZ, e.fY / e.fZ, paint);
}
};
canvas->save();
canvas->translate(5, 5);
canvas->scale(15, 15);
debugster(src);
canvas->restore();
canvas->translate(128, 128);
SkMatrix matrix;
matrix.setAll(15, 0, 0, 0, 15, 0, -0.08, 0.04, 1);
matrix.mapHomogeneousPoints(src, src, count);
debugster(src);
##
#SeeAlso mapPoints mapXY mapVectors
##
# ------------------------------------------------------------------------------
#Method void mapXY(SkScalar x, SkScalar y, SkPoint* result) const
Maps Point (x, y) to result. Point is mapped by multiplying by Matrix. Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
##
result is computed as:
#Code
#Literal
|A B C| |x| Ax+By+C Dx+Ey+F
Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
#Param x x-coordinate of Point to map ##
#Param y y-coordinate of Point to map ##
#Param result storage for mapped Point ##
#Example
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
matrix.setRotate(60, 128, 128);
SkPoint lines[] = {{50, 50}, {150, 50}, {150, 150}};
for (size_t i = 0; i < SK_ARRAY_COUNT(lines); ++i) {
SkPoint pt;
matrix.mapXY(lines[i].fX, lines[i].fY, &pt);
canvas->drawCircle(pt.fX, pt.fY, 3, paint);
}
canvas->concat(matrix);
canvas->drawPoints(SkCanvas::kPolygon_PointMode, SK_ARRAY_COUNT(lines), lines, paint);
##
#SeeAlso mapPoints mapVectors
##
# ------------------------------------------------------------------------------
#Method SkPoint mapXY(SkScalar x, SkScalar y) const
Returns Point (x, y) multiplied by Matrix. Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
##
result is computed as:
#Code
#Literal
|A B C| |x| Ax+By+C Dx+Ey+F
Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
#Param x x-coordinate of Point to map ##
#Param y y-coordinate of Point to map ##
#Return mapped Point ##
#Example
#Image 4
SkMatrix matrix;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {30, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
SkPaint paint;
paint.setAntiAlias(true);
paint.setStrokeWidth(3);
for (int x : { 0, source.width() } ) {
for (int y : { 0, source.height() } ) {
canvas->drawPoint(matrix.mapXY(x, y), paint);
}
}
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso mapPoints mapVectors
##
# ------------------------------------------------------------------------------
#Method void mapVectors(SkVector dst[], const SkVector src[], int count) const
Maps src Vector array of length count to Vector Point array of equal or greater
length. Vectors are mapped by multiplying each Vector by Matrix, treating
Matrix translation as zero. Given:
#Code
#Literal
| A B 0 | | x |
Matrix = | D E 0 |, src = | y |
| G H I | | 1 |
##
where
#Code
#Literal
for (i = 0; i < count; ++i) {
x = src[i].fX
y = src[i].fY
}
##
each dst Vector is computed as:
#Code
#Literal
|A B 0| |x| Ax+By Dx+Ey
Matrix * src = |D E 0| |y| = |Ax+By Dx+Ey Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
src and dst may point to the same storage.
#Param dst storage for mapped Vectors ##
#Param src Vectors to transform ##
#Param count number of Vectors to transform ##
#Example
SkPaint paint;
paint.setAntiAlias(true);
paint.setStyle(SkPaint::kStroke_Style);
SkMatrix matrix;
matrix.reset();
const SkVector radii[] = {{8, 4}, {9, 1}, {6, 2}, {7, 3}};
for (int i = 0; i < 4; ++i) {
SkVector rScaled[4];
matrix.preScale(1.5f, 2.f);
matrix.mapVectors(rScaled, radii, SK_ARRAY_COUNT(radii));
SkRRect rrect;
rrect.setRectRadii({20, 20, 180, 70}, rScaled);
canvas->drawRRect(rrect, paint);
canvas->translate(0, 60);
}
##
#SeeAlso mapVector mapPoints mapXY
##
# ------------------------------------------------------------------------------
#Method void mapVectors(SkVector vecs[], int count) const
Maps vecs Vector array of length count in place, multiplying each Vector by
Matrix, treating Matrix translation as zero. Given:
#Code
#Literal
| A B 0 | | x |
Matrix = | D E 0 |, vec = | y |
| G H I | | 1 |
##
where
#Code
#Literal
for (i = 0; i < count; ++i) {
x = vecs[i].fX
y = vecs[i].fY
}
##
each result Vector is computed as:
#Code
#Literal
|A B 0| |x| Ax+By Dx+Ey
Matrix * vec = |D E 0| |y| = |Ax+By Dx+Ey Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
#Param vecs Vectors to transform, and storage for mapped Vectors ##
#Param count number of Vectors to transform ##
#Example
SkPaint paint;
paint.setAntiAlias(true);
paint.setStyle(SkPaint::kStroke_Style);
SkMatrix matrix;
matrix.setScale(2, 3);
SkVector radii[] = {{7, 7}, {3, 3}, {2, 2}, {4, 0}};
for (int i = 0; i < 4; ++i) {
SkRRect rrect;
rrect.setRectRadii({20, 20, 180, 70}, radii);
canvas->drawRRect(rrect, paint);
canvas->translate(0, 60);
matrix.mapVectors(radii, SK_ARRAY_COUNT(radii));
}
##
#SeeAlso mapVector mapPoints mapXY
##
# ------------------------------------------------------------------------------
#Method void mapVector(SkScalar dx, SkScalar dy, SkVector* result) const
Maps Vector (x, y) to result. Vector is mapped by multiplying by Matrix,
treating Matrix translation as zero. Given:
#Code
#Literal
| A B 0 | | dx |
Matrix = | D E 0 |, vec = | dy |
| G H I | | 1 |
##
each result Vector is computed as:
#Code
#Literal
#Outdent
|A B 0| |dx| A*dx+B*dy D*dx+E*dy
Matrix * vec = |D E 0| |dy| = |A*dx+B*dy D*dx+E*dy G*dx+H*dy+I| = ----------- , -----------
|G H I| | 1| G*dx+H*dy+I G*dx+*dHy+I
##
#Param dx x-coordinate of Vector to map ##
#Param dy y-coordinate of Vector to map ##
#Param result storage for mapped Vector ##
#Example
SkPaint paint;
paint.setColor(SK_ColorGREEN);
paint.setAntiAlias(true);
paint.setTextSize(48);
SkMatrix matrix;
matrix.setRotate(90);
SkVector offset = { 7, 7 };
for (int i = 0; i < 4; ++i) {
paint.setImageFilter(SkDropShadowImageFilter::Make(offset.fX, offset.fY, 3, 3,
SK_ColorBLUE, SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode, nullptr));
matrix.mapVector(offset.fX, offset.fY, &offset);
canvas->translate(0, 60);
canvas->drawString("Text", 50, 0, paint);
}
##
#SeeAlso mapVectors mapPoints mapXY
##
# ------------------------------------------------------------------------------
#Method SkVector mapVector(SkScalar dx, SkScalar dy) const
Returns Vector (x, y) multiplied by Matrix, treating Matrix translation as zero.
Given:
#Code
#Literal
| A B 0 | | dx |
Matrix = | D E 0 |, vec = | dy |
| G H I | | 1 |
##
each result Vector is computed as:
#Code
#Literal
#Outdent
|A B 0| |dx| A*dx+B*dy D*dx+E*dy
Matrix * vec = |D E 0| |dy| = |A*dx+B*dy D*dx+E*dy G*dx+H*dy+I| = ----------- , -----------
|G H I| | 1| G*dx+H*dy+I G*dx+*dHy+I
##
#Param dx x-coordinate of Vector to map ##
#Param dy y-coordinate of Vector to map ##
#Return mapped Vector ##
#Example
SkPaint paint;
paint.setColor(SK_ColorGREEN);
paint.setAntiAlias(true);
paint.setTextSize(48);
SkMatrix matrix;
matrix.setRotate(90);
SkVector offset = { 7, 7 };
for (int i = 0; i < 4; ++i) {
paint.setImageFilter(SkDropShadowImageFilter::Make(offset.fX, offset.fY, 3, 3,
SK_ColorBLUE, SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode, nullptr));
offset = matrix.mapVector(offset.fX, offset.fY);
canvas->translate(0, 60);
canvas->drawString("Text", 50, 0, paint);
}
##
#SeeAlso mapVectors mapPoints mapXY
##
# ------------------------------------------------------------------------------
#Method bool mapRect(SkRect* dst, const SkRect& src) const
Sets dst to bounds of src corners mapped by Matrix.
Returns true if mapped corners are dst corners.
Returned value is the same as calling rectStaysRect.
#Param dst storage for bounds of mapped Points ##
#Param src Rect to map ##
#Return true if dst is equivalent to mapped src ##
#Example
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
matrix.setRotate(45, 128, 128);
SkRect rotatedBounds, bounds = {40, 50, 190, 200};
matrix.mapRect(&rotatedBounds, bounds );
paint.setColor(SK_ColorGRAY);
canvas->drawRect(rotatedBounds, paint);
canvas->concat(matrix);
paint.setColor(SK_ColorRED);
canvas->drawRect(bounds, paint);
##
#SeeAlso mapPoints rectStaysRect
##
# ------------------------------------------------------------------------------
#Method bool mapRect(SkRect* rect) const
Sets rect to bounds of rect corners mapped by Matrix.
Returns true if mapped corners are computed rect corners.
Returned value is the same as calling rectStaysRect.
#Param rect rectangle to map, and storage for bounds of mapped corners ##
#Return true if result is equivalent to mapped src ##
#Example
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
matrix.setRotate(45, 128, 128);
SkRect bounds = {40, 50, 190, 200};
matrix.mapRect(&bounds);
paint.setColor(SK_ColorGRAY);
canvas->drawRect(bounds, paint);
canvas->concat(matrix);
paint.setColor(SK_ColorRED);
canvas->drawRect({40, 50, 190, 200}, paint);
##
#SeeAlso mapRectScaleTranslate mapPoints rectStaysRect
##
# ------------------------------------------------------------------------------
#Method void mapRectToQuad(SkPoint dst[4], const SkRect& rect) const
Maps four corners of rect to dst. Points are mapped by multiplying each
rect corner by Matrix. rect corner is processed in this order:
(rect.fLeft, rect.fTop), (rect.fRight, rect.fTop), (rect.fRight, rect.fBottom),
(rect.fLeft, rect.fBottom).
rect may be empty: rect.fLeft may be greater than or equal to rect.fRight;
rect.fTop may be greater than or equal to rect.fBottom.
Given:
#Code
#Literal
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
##
where pt is initialized from each of (rect.fLeft, rect.fTop),
(rect.fRight, rect.fTop), (rect.fRight, rect.fBottom), (rect.fLeft, rect.fBottom),
each dst Point is computed as:
#Code
#Literal
|A B C| |x| Ax+By+C Dx+Ey+F
Matrix * pt = |D E F| |y| = |Ax+By+C Dx+Ey+F Gx+Hy+I| = ------- , -------
|G H I| |1| Gx+Hy+I Gx+Hy+I
##
#Param dst storage for mapped corner Points ##
#Param rect Rect to map ##
#Example
#Height 192
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
matrix.setRotate(60, 128, 128);
SkRect rect = {50, 50, 150, 150};
SkPoint pts[4];
matrix.mapRectToQuad(pts, rect);
for (int i = 0; i < 4; ++i) {
canvas->drawCircle(pts[i].fX, pts[i].fY, 3, paint);
}
canvas->concat(matrix);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawRect(rect, paint);
##
#SeeAlso mapRect mapRectScaleTranslate
##
# ------------------------------------------------------------------------------
#Method void mapRectScaleTranslate(SkRect* dst, const SkRect& src) const
Sets dst to bounds of src corners mapped by Matrix. If matrix contains
elements other than scale or translate: asserts if SK_DEBUG is defined;
otherwise, results are undefined.
#Param dst storage for bounds of mapped Points ##
#Param src Rect to map ##
#Example
SkPaint paint;
SkMatrix matrix;
SkRect rect = {100, 50, 150, 180};
matrix.setScale(2, .5f, rect.centerX(), rect.centerY());
SkRect rotated;
matrix.mapRectScaleTranslate(&rotated, rect);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawRect(rect, paint);
paint.setColor(SK_ColorRED);
canvas->drawRect(rotated, paint);
##
#SeeAlso mapRect mapRectToQuad isScaleTranslate rectStaysRect
##
# ------------------------------------------------------------------------------
#Method SkScalar mapRadius(SkScalar radius) const
Returns geometric mean radius of ellipse formed by constructing Circle of
size radius, and mapping constructed Circle with Matrix. The result squared is
equal to the major axis length times the minor axis length.
Result is not meaningful if Matrix contains perspective elements.
#Param radius Circle size to map ##
#Return average mapped radius ##
#Example
#Description
The area enclosed by a square with sides equal to mappedRadius is the same as
the area enclosed by the ellipse major and minor axes.
##
SkPaint paint;
paint.setAntiAlias(true);
SkMatrix matrix;
const SkPoint center = {108, 93};
matrix.setScale(2, .5f, center.fX, center.fY);
matrix.postRotate(45, center.fX, center.fY);
const SkScalar circleRadius = 50;
SkScalar mappedRadius = matrix.mapRadius(circleRadius);
SkVector minorAxis, majorAxis;
matrix.mapVector(0, circleRadius, &minorAxis);
matrix.mapVector(circleRadius, 0, &majorAxis);
SkString mappedArea;
mappedArea.printf("area = %g", mappedRadius * mappedRadius);
canvas->drawString(mappedArea, 145, 250, paint);
canvas->drawString("mappedRadius", center.fX + mappedRadius + 3, center.fY, paint);
paint.setColor(SK_ColorRED);
SkString axArea;
axArea.printf("area = %g", majorAxis.length() * minorAxis.length());
paint.setStyle(SkPaint::kFill_Style);
canvas->drawString(axArea, 15, 250, paint);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawRect({10, 200, 10 + majorAxis.length(), 200 + minorAxis.length()}, paint);
paint.setColor(SK_ColorBLACK);
canvas->drawLine(center.fX, center.fY, center.fX + mappedRadius, center.fY, paint);
canvas->drawLine(center.fX, center.fY, center.fX, center.fY + mappedRadius, paint);
canvas->drawRect({140, 180, 140 + mappedRadius, 180 + mappedRadius}, paint);
canvas->concat(matrix);
canvas->drawCircle(center.fX, center.fY, circleRadius, paint);
paint.setColor(SK_ColorRED);
canvas->drawLine(center.fX, center.fY, center.fX + circleRadius, center.fY, paint);
canvas->drawLine(center.fX, center.fY, center.fX, center.fY + circleRadius, paint);
##
#SeeAlso mapVector
##
# ------------------------------------------------------------------------------
#Method bool isFixedStepInX() const
Returns true if a unit step in x at some y mapped through Matrix can be
represented by a constant Vector. Returns true if getType returns kIdentity_Mask,
or combinations of: kTranslate_Mask, kScale_Mask, and kAffine_Mask.
May return true if getType returns kPerspective_Mask, but only when Matrix
does not include rotation or skewing along the y-axis.
#Return true if Matrix does not have complex perspective ##
#Example
SkMatrix matrix;
for (SkScalar px : { 0.0f, 0.1f } ) {
for (SkScalar py : { 0.0f, 0.1f } ) {
for (SkScalar sy : { 1, 2 } ) {
matrix.setAll(1, 0, 0, 0, sy, 0, px, py, 1);
matrix.dump();
SkDebugf("isFixedStepInX: %s\n", matrix.isFixedStepInX() ? "true" : "false");
}
}
}
#StdOut
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
isFixedStepInX: true
[ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.0000 0.0000 1.0000]
isFixedStepInX: true
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.0000 0.1000 1.0000]
isFixedStepInX: true
[ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.0000 0.1000 1.0000]
isFixedStepInX: true
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.1000 0.0000 1.0000]
isFixedStepInX: false
[ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.1000 0.0000 1.0000]
isFixedStepInX: false
[ 1.0000 0.0000 0.0000][ 0.0000 1.0000 0.0000][ 0.1000 0.1000 1.0000]
isFixedStepInX: false
[ 1.0000 0.0000 0.0000][ 0.0000 2.0000 0.0000][ 0.1000 0.1000 1.0000]
isFixedStepInX: false
##
##
#SeeAlso fixedStepInX getType
##
# ------------------------------------------------------------------------------
#Method SkVector fixedStepInX(SkScalar y) const
Returns Vector representing a unit step in x at y mapped through Matrix.
If isFixedStepInX is false, returned value is undefined.
#Param y position of line parallel to x-axis ##
#Return Vector advance of mapped unit step in x ##
#Example
#Image 3
SkMatrix matrix;
const SkPoint center = { 128, 128 };
matrix.setScale(20, 25, center.fX, center.fY);
matrix.postRotate(75, center.fX, center.fY);
{
SkAutoCanvasRestore acr(canvas, true);
canvas->concat(matrix);
canvas->drawBitmap(source, 0, 0);
}
if (matrix.isFixedStepInX()) {
SkPaint paint;
paint.setAntiAlias(true);
SkVector step = matrix.fixedStepInX(128);
SkVector end = center + step;
canvas->drawLine(center, end, paint);
SkVector arrow = { step.fX + step.fY, step.fY - step.fX};
arrow = arrow * .25f;
canvas->drawLine(end, end - arrow, paint);
canvas->drawLine(end, {end.fX + arrow.fY, end.fY - arrow.fX}, paint);
}
##
#SeeAlso isFixedStepInX getType
##
# ------------------------------------------------------------------------------
#Method bool cheapEqualTo(const SkMatrix& m) const
Returns true if Matrix equals m, using an efficient comparison.
Returns false when the sign of zero values is the different; when one
matrix has positive zero value and the other has negative zero value.
Returns true even when both Matrices contain NaN.
NaN never equals any value, including itself. To improve performance, NaN values
are treated as bit patterns that are equal if their bit patterns are equal.
#Param m Matrix to compare ##
#Return true if m and Matrix are represented by identical bit patterns ##
#Example
auto debugster = [](const char* prefix, const SkMatrix& a, const SkMatrix& b) -> void {
SkDebugf("%s: a %c= b a.cheapEqualTo(b): %s\n", prefix,
a == b ? '=' : '!', a.cheapEqualTo(b) ? "true" : "false");
};
SkMatrix a, b;
a.setAll(1, 0, 0, 0, 1, 0, 0, 0, 1);
b.setIdentity();
debugster("identity", a, b);
a.setAll(1, -0.0f, 0, 0, 1, 0, 0, 0, 1);
debugster("neg zero", a, b);
a.setAll(1, SK_ScalarNaN, 0, 0, 1, 0, 0, 0, 1);
debugster(" one NaN", a, b);
b.setAll(1, SK_ScalarNaN, 0, 0, 1, 0, 0, 0, 1);
debugster("both NaN", a, b);
#StdOut
identity: a == b a.cheapEqualTo(b): true
neg zero: a == b a.cheapEqualTo(b): false
one NaN: a != b a.cheapEqualTo(b): false
both NaN: a != b a.cheapEqualTo(b): true
##
##
#SeeAlso operator==(const SkMatrix& a, const SkMatrix& b)
##
# ------------------------------------------------------------------------------
#Method bool operator==(const SkMatrix& a, const SkMatrix& b)
Compares a and b; returns true if a and b are numerically equal. Returns true
even if sign of zero values are different. Returns false if either Matrix
contains NaN, even if the other Matrix also contains NaN.
#Param a Matrix to compare ##
#Param b Matrix to compare ##
#Return true if m and Matrix are numerically equal ##
#Example
auto debugster = [](const char* prefix, const SkMatrix& a, const SkMatrix& b) -> void {
SkDebugf("%s: a %c= b a.cheapEqualTo(b): %s\n", prefix,
a == b ? '=' : '!', a.cheapEqualTo(b) ? "true" : "false");
};
SkMatrix a, b;
a.setAll(1, 0, 0, 0, 1, 0, 0, 0, 1);
b.setScale(2, 4);
b.postScale(0.5f, 0.25f);
debugster("identity", a, b);
#StdOut
identity: a == b a.cheapEqualTo(b): true
##
##
#SeeAlso cheapEqualTo operator!=(const SkMatrix& a, const SkMatrix& b)
##
# ------------------------------------------------------------------------------
#Method bool operator!=(const SkMatrix& a, const SkMatrix& b)
Compares a and b; returns true if a and b are not numerically equal. Returns false
even if sign of zero values are different. Returns true if either Matrix
contains NaN, even if the other Matrix also contains NaN.
#Param a Matrix to compare ##
#Param b Matrix to compare ##
#Return true if m and Matrix are numerically not equal ##
#Example
auto debugster = [](const char* prefix, const SkMatrix& a, const SkMatrix& b) -> void {
SkDebugf("%s: a %c= b a.cheapEqualTo(b): %s\n", prefix,
a != b ? '!' : '=', a.cheapEqualTo(b) ? "true" : "false");
};
SkMatrix a, b;
a.setAll(1, 0, 0, 0, 1, 0, 1, 0, 1);
a.invert(&b);
debugster("identity", a, b);
##
#SeeAlso cheapEqualTo operator==(const SkMatrix& a, const SkMatrix& b)
##
# ------------------------------------------------------------------------------
#Method void dump() const
Writes text representation of Matrix to standard output. Floating point values
are written with limited precision; it may not be possible to reconstruct
original Matrix from output.
#Example
SkMatrix matrix;
matrix.setRotate(45);
matrix.dump();
SkMatrix nearlyEqual;
nearlyEqual.setAll(0.7071f, -0.7071f, 0, 0.7071f, 0.7071f, 0, 0, 0, 1);
nearlyEqual.dump();
SkDebugf("matrix %c= nearlyEqual\n", matrix == nearlyEqual ? '=' : '!');
#StdOut
[ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000]
[ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000]
matrix != nearlyEqual
##
##
#SeeAlso toString
##
# ------------------------------------------------------------------------------
#Method void toString(SkString* str) const
Creates string representation of Matrix. Floating point values
are written with limited precision; it may not be possible to reconstruct
original Matrix from output.
#Param str storage for string representation of Matrix ##
#Example
SkMatrix matrix;
matrix.setRotate(45);
SkString mStr, neStr;
matrix.toString(&mStr);
SkMatrix nearlyEqual;
nearlyEqual.setAll(0.7071f, -0.7071f, 0, 0.7071f, 0.7071f, 0, 0, 0, 1);
nearlyEqual.toString(&neStr);
SkDebugf("mStr %s\n", mStr.c_str());
SkDebugf("neStr %s\n", neStr.c_str());
SkDebugf("matrix %c= nearlyEqual\n", matrix == nearlyEqual ? '=' : '!');
#StdOut
mStr [ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000]
neStr [ 0.7071 -0.7071 0.0000][ 0.7071 0.7071 0.0000][ 0.0000 0.0000 1.0000]
matrix != nearlyEqual
##
##
#SeeAlso dump
##
# ------------------------------------------------------------------------------
#Method SkScalar getMinScale() const
Returns the minimum scaling factor of Matrix by decomposing the scaling and
skewing elements.
Returns -1 if scale factor overflows or Matrix contains perspective.
#Return minimum scale factor
##
#Example
SkMatrix matrix;
matrix.setScale(42, 24);
SkDebugf("matrix.getMinScale() %g\n", matrix.getMinScale());
#StdOut
matrix.getMinScale() 24
##
##
#SeeAlso getMaxScale getMinMaxScales
##
# ------------------------------------------------------------------------------
#Method SkScalar getMaxScale() const
Returns the maximum scaling factor of Matrix by decomposing the scaling and
skewing elements.
Returns -1 if scale factor overflows or Matrix contains perspective.
#Return maximum scale factor
##
#Example
SkMatrix matrix;
matrix.setScale(42, 24);
SkDebugf("matrix.getMaxScale() %g\n", matrix.getMaxScale());
#StdOut
matrix.getMaxScale() 42
##
##
#SeeAlso getMinScale getMinMaxScales
##
# ------------------------------------------------------------------------------
#Method bool SK_WARN_UNUSED_RESULT getMinMaxScales(SkScalar scaleFactors[2]) const
Sets scaleFactors[0] to the minimum scaling factor, and scaleFactors[1] to the
maximum scaling factor. Scaling factors are computed by decomposing
the Matrix scaling and skewing elements.
Returns true if scaleFactors are found; otherwise, returns false and sets
scaleFactors to undefined values.
#Param scaleFactors storage for minimum and maximum scale factors ##
#Return true if scale factors were computed correctly ##
#Example
SkMatrix matrix;
matrix.setAll(1, 0, 0, 0, 1, 0, 0, 0, 0);
matrix.invert(&matrix);
SkScalar factor[2] = {2, 2};
bool result = matrix.getMinMaxScales(factor);
SkDebugf("matrix.getMinMaxScales() %s %g %g\n", result ? "true" : "false", factor[0], factor[1]);
#StdOut
matrix.getMinMaxScales() false 2 2
##
##
#SeeAlso getMinScale getMaxScale
##
# ------------------------------------------------------------------------------
#Method bool decomposeScale(SkSize* scale, SkMatrix* remaining = nullptr) const
Decomposes Matrix into scale components and whatever remains. Returns false if
Matrix could not be decomposed.
Sets scale to portion of Matrix that scales in x and y. Sets remaining to Matrix
with x and y scaling factored out. remaining may be passed as nullptr
to determine if Matrix can be decomposed without computing remainder.
Returns true if scale components are found. scale and remaining are
unchanged if Matrix contains perspective; scale factors are not finite, or
are nearly zero.
On success
#Formula
Matrix = scale * Remaining
##
#Param scale x and y scaling factors; may be nullptr ##
#Param remaining Matrix without scaling; may be nullptr ##
#Return true if scale can be computed ##
#Example
SkMatrix matrix;
matrix.setRotate(90 * SK_Scalar1);
matrix.postScale(1.f / 4, 1.f / 2);
matrix.dump();
SkSize scale = {SK_ScalarNaN, SK_ScalarNaN};
SkMatrix remaining;
remaining.reset();
bool success = matrix.decomposeScale(&scale, &remaining);
SkDebugf("success: %s ", success ? "true" : "false");
SkDebugf("scale: %g, %g\n", scale.width(), scale.height());
remaining.dump();
SkMatrix scaleMatrix = SkMatrix::MakeScale(scale.width(), scale.height());
SkMatrix combined = SkMatrix::Concat(scaleMatrix, remaining);
combined.dump();
#StdOut
[ 0.0000 -0.2500 0.0000][ 0.5000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
success: true scale: 0.5, 0.25
[ 0.0000 -0.5000 0.0000][ 2.0000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
[ 0.0000 -0.2500 0.0000][ 0.5000 0.0000 0.0000][ 0.0000 0.0000 1.0000]
##
##
#SeeAlso setScale MakeScale
##
# ------------------------------------------------------------------------------
#Method static const SkMatrix& I()
Returns reference to const identity Matrix. Returned Matrix is set to:
#Code
#Literal
| 1 0 0 |
| 0 1 0 |
| 0 0 1 |
##
#Return const identity Matrix ##
#Example
SkMatrix m1, m2, m3;
m1.reset();
m2.setIdentity();
m3 = SkMatrix::I();
SkDebugf("m1 %c= m2\n", m1 == m2 ? '=' : '!');
SkDebugf("m2 %c= m3\n", m1 == m2 ? '=' : '!');
#StdOut
m1 == m2
m2 == m3
##
##
#SeeAlso reset() setIdentity
##
# ------------------------------------------------------------------------------
#Method static const SkMatrix& InvalidMatrix()
Returns reference to a const Matrix with invalid values. Returned Matrix is set
to:
#Code
#Literal
| SK_ScalarMax SK_ScalarMax SK_ScalarMax |
| SK_ScalarMax SK_ScalarMax SK_ScalarMax |
| SK_ScalarMax SK_ScalarMax SK_ScalarMax |
##
#Return const invalid Matrix ##
#Example
SkDebugf("scaleX %g\n", SkMatrix::InvalidMatrix().getScaleX());
#StdOut
scaleX 3.40282e+38
##
##
#SeeAlso SeeAlso getType
##
# ------------------------------------------------------------------------------
#Method static SkMatrix Concat(const SkMatrix& a, const SkMatrix& b)
Returns Matrix a multiplied by Matrix b.
Given:
#Code
#Literal
| A B C | | J K L |
a = | D E F |, b = | M N O |
| G H I | | P Q R |
##
sets Matrix to:
#Code
#Literal
| A B C | | J K L | | AJ+BM+CP AK+BN+CQ AL+BO+CR |
a * b = | D E F | * | M N O | = | DJ+EM+FP DK+EN+FQ DL+EO+FR |
| G H I | | P Q R | | GJ+HM+IP GK+HN+IQ GL+HO+IR |
##
#Param a Matrix on left side of multiply expression ##
#Param b Matrix on right side of multiply expression ##
#Return Matrix computed from a times b ##
#Example
#Height 64
#Image 4
#Description
setPolyToPoly creates perspective matrices, one the inverse of the other.
Multiplying the matrix by its inverse turns into an identity matrix.
##
SkMatrix matrix, matrix2;
SkPoint bitmapBounds[4], perspect[4] = {{50, 10}, {180, 40}, {236, 176}, {10, 206}};
SkRect::Make(source.bounds()).toQuad(bitmapBounds);
matrix.setPolyToPoly(bitmapBounds, perspect, 4);
matrix2.setPolyToPoly(perspect, bitmapBounds, 4);
SkMatrix concat = SkMatrix::Concat(matrix, matrix2);
canvas->concat(concat);
canvas->drawBitmap(source, 0, 0);
##
#SeeAlso preConcat postConcat
##
# ------------------------------------------------------------------------------
#Method void dirtyMatrixTypeCache()
Sets internal cache to unknown state. Use to force update after repeated
modifications to Matrix element reference returned by operator[](int index).
#Example
SkMatrix matrix;
matrix.setIdentity();
SkDebugf("with identity matrix: x = %g\n", matrix.mapXY(24, 42).fX);
SkScalar& skewRef = matrix[SkMatrix::kMSkewX];
skewRef = 0;
SkDebugf("after skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
skewRef = 1;
SkDebugf("after 2nd skew x mod: x = %g\n", matrix.mapXY(24, 42).fX);
matrix.dirtyMatrixTypeCache();
SkDebugf("after dirty cache: x = %g\n", matrix.mapXY(24, 42).fX);
#StdOut
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 24
after dirty cache: x = 66
##
##
#SeeAlso operator[](int index) getType
##
# ------------------------------------------------------------------------------
#Method void setScaleTranslate(SkScalar sx, SkScalar sy, SkScalar tx, SkScalar ty)
Initializes Matrix with scale and translate elements.
#Code
#Literal
| sx 0 tx |
| 0 sy ty |
| 0 0 1 |
##
#Param sx horizontal scale factor to store ##
#Param sy vertical scale factor to store ##
#Param tx horizontal translation to store ##
#Param ty vertical translation to store ##
#Example
SkMatrix matrix;
matrix.setScaleTranslate(1, 2, 3, 4);
matrix.dump();
#StdOut
[ 1.0000 0.0000 3.0000][ 0.0000 2.0000 4.0000][ 0.0000 0.0000 1.0000]
##
##
#SeeAlso setScale preTranslate postTranslate
##
# ------------------------------------------------------------------------------
#Method bool isFinite() const
Returns true if all elements of the matrix are finite. Returns false if any
element is infinity, or NaN.
#Return true if matrix has only finite elements ##
#Example
SkMatrix matrix = SkMatrix::MakeTrans(SK_ScalarNaN, 0);
matrix.dump();
SkDebugf("matrix is finite: %s\n", matrix.isFinite() ? "true" : "false");
SkDebugf("matrix %c= matrix\n", matrix == matrix ? '=' : '!');
#StdOut
[ 1.0000 0.0000 nan][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
matrix is finite: false
matrix != matrix
##
##
#SeeAlso operator==
##
#Class SkMatrix ##
#Topic Matrix ##
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