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SkMatrix Reference
Matrix
Class SkMatrix
Constant
SkMatrix related constants are defined by enum, enum class, #define, const, and constexpr.
| Topic | Description |
|---|---|
| ScaleToFit | options to map Rects |
| TypeMask | bit field for Matrix complexity |
| kAScaleX | horizontal scale factor |
| kAScaleY | vertical scale factor |
| kASkewX | horizontal skew factor |
| kASkewY | vertical skew factor |
| kATransX | horizontal translation |
| kATransY | vertical translation |
| kAffine Mask | skew or rotate Matrix |
| kCenter ScaleToFit | scales and aligns to center |
| kEnd ScaleToFit | scales and aligns to right and bottom |
| kFill ScaleToFit | scales in x and y to fill destination Rect |
| kIdentity Mask | identity Matrix; all bits clear |
| kMPersp0 | input x perspective factor |
| kMPersp1 | input y perspective factor |
| kMPersp2 | perspective bias |
| kMScaleX | horizontal scale factor |
| kMScaleY | vertical scale factor |
| kMSkewX | horizontal skew factor |
| kMSkewY | vertical skew factor |
| kMTransX | horizontal translation |
| kMTransY | vertical translation |
| kPerspective Mask | perspective Matrix |
| kScale Mask | scale Matrix |
| kStart ScaleToFit | scales and aligns to left and top |
| kTranslate Mask | translation Matrix |
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.
Overview
| Topic | Description |
|---|---|
| Constants | enum and enum class, and their const values |
| Constructors | functions that construct SkMatrix |
| Functions | global and class member functions |
| Operators | operator overloading methods |
| Related Functions | similar member functions grouped together |
Member Function
SkMatrix member functions read and modify the structure properties.
| Topic | Description |
|---|---|
| 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 |
Related Function
SkMatrix global, struct, and class related member functions share a topic.
| Topic | Description |
|---|---|
| AffineIndex | affine member indices |
| MemberIndex | member indices |
| Property | values and attributes |
| Set | sets one or more matrix values |
| Transform | map points with Matrix |
| Utility | rarely called management functions |
Constructor
SkMatrix can be constructed or initialized by these functions, including C++ class constructors.
MakeScale
static SkMatrix SK_WARN_UNUSED_RESULT MakeScale(SkScalar sx, SkScalar sy)
Sets Matrix to scale by (sx, sy). Returned matrix is:
| sx 0 0 | | 0 sy 0 | | 0 0 1 |
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
Return Value
Matrix with scale
Example
See Also
setScale[2] postScale[2] preScale[2]
static SkMatrix SK_WARN_UNUSED_RESULT MakeScale(SkScalar scale)
Sets Matrix to scale by (scale, scale). Returned matrix is:
| scale 0 0 | | 0 scale 0 | | 0 0 1 |
Parameters
scale |
horizontal and vertical scale factor |
Return Value
Example
See Also
setScale[2] postScale[2] preScale[2]
MakeTrans
static SkMatrix SK_WARN_UNUSED_RESULT MakeTrans(SkScalar dx, SkScalar dy)
Sets Matrix to translate by (dx, dy). Returned matrix is:
| 1 0 dx | | 0 1 dy | | 0 0 1 |
Parameters
dx |
horizontal translation |
dy |
vertical translation |
Return Value
Matrix with translation
Example
See Also
setTranslate[2] postTranslate preTranslate
MakeAll
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:
| scaleX skewX transX | | skewY scaleY transY | | pers0 pers1 pers2 |
Parameters
scaleX |
horizontal scale factor |
skewX |
horizontal skew factor |
transX |
horizontal translation |
skewY |
vertical skew factor |
scaleY |
vertical scale factor |
transY |
vertical translation |
pers0 |
input x perspective factor |
pers1 |
input y perspective factor |
pers2 |
perspective scale factor |
Return Value
Matrix constructed from parameters
Example
See Also
setAll set9 postConcat preConcat
Enum SkMatrix::TypeMask
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.
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::kIdentity_Mask |
0 | all bits clear if Matrix is identity |
SkMatrix::kTranslate_Mask |
1 | set if Matrix has translation |
SkMatrix::kScale_Mask |
2 | set if Matrix has x or y scale |
SkMatrix::kAffine_Mask |
4 | set if Matrix skews or rotates |
SkMatrix::kPerspective_Mask |
8 | set if Matrix has perspective |
Example
Example Output
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
See Also
Property
| Topic | Description |
|---|---|
| decomposeScale | separates scale if possible |
| 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 |
| 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 |
| 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 |
getType
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 Value
kIdentity Mask, or combinations of: kTranslate Mask, kScale Mask, kAffine Mask, kPerspective Mask
Example
Example Output
identity flags hex: 0 decimal: 0
set all flags hex: f decimal: 15
See Also
isIdentity
bool isIdentity() const
Returns true if Matrix is identity. Identity matrix is:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Return Value
true if Matrix has no effect
Example
Example Output
is identity: true
is identity: false
See Also
isScaleTranslate
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:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
Return Value
true if Matrix is identity; or scales, translates, or both
Example
Example Output
is scale-translate: true
is scale-translate: true
is scale-translate: true
is scale-translate: true
See Also
setScale[2] isTranslate setTranslate[2] getType
isTranslate
bool isTranslate() const
Returns true if Matrix is identity, or translates. Matrix form is:
| 1 0 translate-x | | 0 1 translate-y | | 0 0 1 |
Return Value
true if Matrix is identity, or translates
Example
Example Output
is translate: true
is translate: true
is translate: false
is translate: false
See Also
rectStaysRect
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:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
or
| 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 Value
true if Matrix maps one Rect into another
Example
Example Output
rectStaysRect: true
rectStaysRect: true
rectStaysRect: true
rectStaysRect: true
See Also
preservesAxisAlignment preservesRightAngles
preservesAxisAlignment
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:
| scale-x 0 translate-x | | 0 scale-y translate-y | | 0 0 1 |
or
| 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 Value
true if Matrix maps one Rect into another
Example
Example Output
preservesAxisAlignment: true
preservesAxisAlignment: true
preservesAxisAlignment: true
preservesAxisAlignment: true
See Also
rectStaysRect preservesRightAngles
hasPerspective
bool hasPerspective() const
Returns true if the matrix contains perspective elements. Matrix form is:
| -- -- -- | | -- -- -- | | 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 Value
true if Matrix is in most general form
Example
See Also
isSimilarity
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.
Parameters
tol |
to be deprecated |
Return Value
true if Matrix only rotates, uniformly scales, translates
Example
See Also
isScaleTranslate preservesRightAngles rectStaysRect isFixedStepInX
preservesRightAngles
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.
Parameters
tol |
to be deprecated |
Return Value
true if Matrix only rotates, scales, translates
Example
See Also
isScaleTranslate isSimilarity rectStaysRect isFixedStepInX
MemberIndex
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::kMScaleX |
0 | horizontal scale factor |
SkMatrix::kMSkewX |
1 | horizontal skew factor |
SkMatrix::kMTransX |
2 | horizontal translation |
SkMatrix::kMSkewY |
3 | vertical skew factor |
SkMatrix::kMScaleY |
4 | vertical scale factor |
SkMatrix::kMTransY |
5 | vertical translation |
SkMatrix::kMPersp0 |
6 | input x perspective factor |
SkMatrix::kMPersp1 |
7 | input y perspective factor |
SkMatrix::kMPersp2 |
8 | perspective bias |
static constexpr int kMScaleX = 0; static constexpr int kMSkewX = 1; static constexpr int kMTransX = 2; static constexpr int kMSkewY = 3; static constexpr int kMScaleY = 4; static constexpr int kMTransY = 5; static constexpr int kMPersp0 = 6; static constexpr int kMPersp1 = 7; static constexpr int kMPersp2 = 8;
Matrix organizes its values in row order. These members correspond to each value in Matrix.
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::kMScaleX |
0 | horizontal scale factor |
SkMatrix::kMSkewX |
1 | horizontal skew factor |
SkMatrix::kMTransX |
2 | horizontal translation |
SkMatrix::kMSkewY |
3 | vertical skew factor |
SkMatrix::kMScaleY |
4 | vertical scale factor |
SkMatrix::kMTransY |
5 | vertical translation |
SkMatrix::kMPersp0 |
6 | input x perspective factor |
SkMatrix::kMPersp1 |
7 | input y perspective factor |
SkMatrix::kMPersp2 |
8 | perspective bias |
Example
See Also
AffineIndex
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::kAScaleX |
0 | horizontal scale factor |
SkMatrix::kASkewY |
1 | vertical skew factor |
SkMatrix::kASkewX |
2 | horizontal skew factor |
SkMatrix::kAScaleY |
3 | vertical scale factor |
SkMatrix::kATransX |
4 | horizontal translation |
SkMatrix::kATransY |
5 | vertical translation |
static constexpr int kAScaleX = 0; static constexpr int kASkewY = 1; static constexpr int kASkewX = 2; static constexpr int kAScaleY = 3; static constexpr int kATransX = 4; static constexpr int kATransY = 5;
Affine arrays are in column major order to match the matrix used by PDF and XPS.
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::kAScaleX |
0 | horizontal scale factor |
SkMatrix::kASkewY |
1 | vertical skew factor |
SkMatrix::kASkewX |
2 | horizontal skew factor |
SkMatrix::kAScaleY |
3 | vertical scale factor |
SkMatrix::kATransX |
4 | horizontal translation |
SkMatrix::kATransY |
5 | vertical translation |
See Also
SetAffineIdentity asAffine setAffine
Operator
SkMatrix operators inline class member functions with arithmetic equivalents.
| Topic | Description |
|---|---|
| Concat | returns the concatenation of Matrix pair |
| cheapEqualTo | compares Matrix pair using memcmp() |
| invert | returns inverse, if possible |
| 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) | returns writable reference to Matrix value |
| operator[](int index) const | returns Matrix value |
operator[]
SkScalar operator[](int index) _const
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is defined.
Parameters
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2 |
Return Value
value corresponding to index
Example
Example Output
matrix[SkMatrix::kMScaleX] == 42
matrix[SkMatrix::kMScaleY] == 24
See Also
get
SkScalar get(int index) const
Returns one matrix value. Asserts if index is out of range and SK_DEBUG is defined.
Parameters
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2 |
Return Value
value corresponding to index
Example
Example Output
matrix.get(SkMatrix::kMSkewX) == 42
matrix.get(SkMatrix::kMSkewY) == 24
See Also
getScaleX
SkScalar getScaleX() const
Returns scale factor multiplied by x input, contributing to x output. With mapPoints, scales Points along the x-axis.
Return Value
horizontal scale factor
Example
Example Output
matrix.getScaleX() == 42
See Also
get getScaleY setScaleX setScale[2]
getScaleY
SkScalar getScaleY() const
Returns scale factor multiplied by y input, contributing to y output. With mapPoints, scales Points along the y-axis.
Return Value
vertical scale factor
Example
Example Output
matrix.getScaleY() == 24
See Also
get getScaleX setScaleY setScale[2]
getSkewY
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 Value
vertical skew factor
Example
Example Output
matrix.getSkewY() == 24
See Also
get getSkewX setSkewY setSkew[2]
getSkewX
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 Value
horizontal scale factor
Example
Example Output
matrix.getSkewX() == 42
See Also
get getSkewY setSkewX setSkew[2]
getTranslateX
SkScalar getTranslateX() const
Returns translation contributing to x output. With mapPoints, moves Points along the x-axis.
Return Value
horizontal translation factor
Example
Example Output
matrix.getTranslateX() == 42
See Also
get getTranslateY setTranslateX setTranslate[2]
getTranslateY
SkScalar getTranslateY() const
Returns translation contributing to y output. With mapPoints, moves Points along the y-axis.
Return Value
vertical translation factor
Example
Example Output
matrix.getTranslateY() == 24
See Also
get getTranslateX setTranslateY setTranslate[2]
getPerspX
SkScalar getPerspX() const
Returns factor scaling input x relative to input y.
Return Value
input x perspective factor
Example
See Also
getPerspY
SkScalar getPerspY() const
Returns factor scaling input y relative to input x.
Return Value
input y perspective factor
Example
See Also
operator[]
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.
Parameters
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2 |
Return Value
writable value corresponding to index
Example
Example Output
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 24
after dirty cache: x = 66
See Also
Set
set
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.
Parameters
index |
one of: kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY, kMPersp0, kMPersp1, kMPersp2 |
value |
Scalar to store in Matrix |
Example
Example Output
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 66
See Also
operator[] get
setScaleX
void setScaleX(SkScalar v)
Sets horizontal scale factor.
Parameters
v |
horizontal scale factor to store |
Example
See Also
setScaleY
void setScaleY(SkScalar v)
Sets vertical scale factor.
Parameters
v |
vertical scale factor to store |
Example
See Also
setSkewY
void setSkewY(SkScalar v)
Sets vertical skew factor.
Parameters
v |
vertical skew factor to store |
Example
See Also
setSkewX
void setSkewX(SkScalar v)
Sets horizontal skew factor.
Parameters
v |
horizontal skew factor to store |
Example
See Also
setTranslateX
void setTranslateX(SkScalar v)
Sets horizontal translation.
Parameters
v |
horizontal translation to store |
Example
See Also
set setTranslate[2] setTranslateY
setTranslateY
void setTranslateY(SkScalar v)
Sets vertical translation.
Parameters
v |
vertical translation to store |
Example
See Also
set setTranslate[2] setTranslateX
setPerspX
void setPerspX(SkScalar v)
Sets input x perspective factor, which causes mapXY to vary input x inversely proportional to input y.
Parameters
v |
perspective factor |
Example
See Also
getPerspX set setAll set9 MakeAll
setPerspY
void setPerspY(SkScalar v)
Sets input y perspective factor, which causes mapXY to vary input y inversely proportional to input x.
Parameters
v |
perspective factor |
Example
See Also
getPerspY set setAll set9 MakeAll
setAll
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:
| scaleX skewX transX | | skewY scaleY transY | | persp0 persp1 persp2 |
Parameters
scaleX |
horizontal scale factor to store |
skewX |
horizontal skew factor to store |
transX |
horizontal translation to store |
skewY |
vertical skew factor to store |
scaleY |
vertical scale factor to store |
transY |
vertical translation to store |
persp0 |
input x perspective factor to store |
persp1 |
input y perspective factor to store |
persp2 |
perspective scale factor to store |
Example
See Also
get9
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.
Parameters
buffer |
storage for nine Scalar values |
Example
Example Output
{4, 0, 3},
{0, 5, 4},
{0, 0, 1}
See Also
set9
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:
| 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.
Parameters
buffer |
nine Scalar values |
Example
See Also
reset
void reset()
Sets Matrix to identity; which has no effect on mapped Points. Sets Matrix to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Also called setIdentity; use the one that provides better inline documentation.
Example
Example Output
m.isIdentity(): true
See Also
setIdentity
void setIdentity()
Sets Matrix to identity; which has no effect on mapped Points. Sets Matrix to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Also called reset; use the one that provides better inline documentation.
Example
Example Output
m.isIdentity(): true
See Also
setTranslate
void setTranslate(SkScalar dx, SkScalar dy)
Sets Matrix to translate by (dx, dy).
Parameters
dx |
horizontal translation |
dy |
vertical translation |
Example
See Also
void setTranslate(const SkVector& v)
Sets Matrix to translate by (v.fX, v.fY).
Parameters
v |
Vector containing horizontal and vertical translation |
Example
See Also
setTranslateX setTranslateY MakeTrans
setScale
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.
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot x |
py |
pivot y |
Example
See Also
setScaleX setScaleY MakeScale[2] preScale[2] postScale[2]
void setScale(SkScalar sx, SkScalar sy)
Sets Matrix to scale by sx and sy about at pivot point at (0, 0).
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
Example
See Also
setScaleX setScaleY MakeScale[2] preScale[2] postScale[2]
setRotate
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.
Parameters
degrees |
angle of axes relative to upright axes |
px |
pivot x |
py |
pivot y |
Example
See Also
setSinCos[2] preRotate[2] postRotate[2]
void setRotate(SkScalar degrees)
Sets Matrix to rotate by degrees about a pivot point at (0, 0). Positive degrees rotates clockwise.
Parameters
degrees |
angle of axes relative to upright axes |
Example
See Also
setSinCos[2] preRotate[2] postRotate[2]
setSinCos
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.
Parameters
sinValue |
rotation vector x component |
cosValue |
rotation vector y component |
px |
pivot x |
py |
pivot y |
Example
See Also
setRotate[2] setScale[2] setRSXform
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.
Parameters
sinValue |
rotation vector x component |
cosValue |
rotation vector y component |
Example
See Also
setRotate[2] setScale[2] setRSXform
setRSXform
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).
Parameters
rsxForm |
compressed RSXform matrix |
Return Value
reference to Matrix
Example
See Also
setSinCos[2] setScale[2] setTranslate[2]
setSkew
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.
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot x |
py |
pivot y |
Example
See Also
setSkewX setSkewY preSkew[2] postSkew[2]
void setSkew(SkScalar kx, SkScalar ky)
Sets Matrix to skew by kx and ky, about a pivot point at (0, 0).
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
Example
See Also
setSkewX setSkewY preSkew[2] postSkew[2]
setConcat
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:
| A B C | | J K L |
a = | D E F |, b = | M N O |
| G H I | | P Q R |
sets Matrix to:
| 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 |
Parameters
a |
Matrix on left side of multiply expression |
b |
Matrix on right side of multiply expression |
Example
See Also
Concat preConcat postConcat SkCanvas::concat
preTranslate
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:
| 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:
| 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 |
Parameters
dx |
x translation before applying Matrix |
dy |
y translation before applying Matrix |
Example
See Also
postTranslate setTranslate[2] MakeTrans
preScale
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:
| 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
dx = px - sx * px dy = py - sy * py
sets Matrix to:
| 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 |
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot x |
py |
pivot y |
Example
See Also
postScale[2] setScale[2] MakeScale[2]
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:
| 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:
| 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 |
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
Example
See Also
postScale[2] setScale[2] MakeScale[2]
preRotate
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:
| A B C | | c -s dx |
Matrix = | D E F |, R(degrees, px, py) = | s c dy |
| G H I | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees) dx = s * py + (1 - c) * px dy = -s * px + (1 - c) * py
sets Matrix to:
| 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 |
Parameters
degrees |
angle of axes relative to upright axes |
px |
pivot x |
py |
pivot y |
Example
See Also
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:
| A B C | | c -s 0 |
Matrix = | D E F |, R(degrees, px, py) = | s c 0 |
| G H I | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees)
sets Matrix to:
| 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 |
Parameters
degrees |
angle of axes relative to upright axes |
Example
See Also
preSkew
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:
| 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
dx = -kx * py dy = -ky * px
sets Matrix to:
| 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 |
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot x |
py |
pivot y |
Example
See Also
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:
| 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:
| 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 |
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
Example
See Also
preConcat
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:
| A B C | | J K L |
Matrix = | D E F |, other = | M N O |
| G H I | | P Q R |
sets Matrix to:
| 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 |
Parameters
other |
Matrix on right side of multiply expression |
Example
See Also
postTranslate
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:
| 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:
| 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 |
Parameters
dx |
x translation after applying Matrix |
dy |
y translation after applying Matrix |
Example
See Also
preTranslate setTranslate[2] MakeTrans
postScale
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:
| 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
dx = px - sx * px dy = py - sy * py
sets Matrix to:
| 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 |
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
px |
pivot x |
py |
pivot y |
Example
See Also
preScale[2] setScale[2] MakeScale[2]
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:
| 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:
| 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 |
Parameters
sx |
horizontal scale factor |
sy |
vertical scale factor |
Example
See Also
preScale[2] setScale[2] MakeScale[2]
postIDiv
bool postIDiv(int divx, int divy)
Sets Matrix to Matrix constructed from scaling by(1/divx, 1/divy) about pivot point (px, py), multiplied by Matrix.
Returns false if either divx or divy is zero.
Given:
| J K L | | sx 0 0 |
Matrix = | M N O |, I(divx, divy) = | 0 sy 0 |
| P Q R | | 0 0 1 |
where
sx = 1 / divx sy = 1 / divy
sets Matrix to:
| 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 |
Parameters
divx |
integer divisor for inverse scale in x |
divy |
integer divisor for inverse scale in y |
Return Value
true on successful scale
Example
See Also
postRotate
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:
| J K L | | c -s dx |
Matrix = | M N O |, R(degrees, px, py) = | s c dy |
| P Q R | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees) dx = s * py + (1 - c) * px dy = -s * px + (1 - c) * py
sets Matrix to:
|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|
Parameters
degrees |
angle of axes relative to upright axes |
px |
pivot x |
py |
pivot y |
Example
See Also
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:
| J K L | | c -s 0 |
Matrix = | M N O |, R(degrees, px, py) = | s c 0 |
| P Q R | | 0 0 1 |
where
c = cos(degrees) s = sin(degrees)
sets Matrix to:
| 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 |
Parameters
degrees |
angle of axes relative to upright axes |
Example
See Also
postSkew
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:
| 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
dx = -kx * py dy = -ky * px
sets Matrix to:
| 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|
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
px |
pivot x |
py |
pivot y |
Example
See Also
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:
| 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:
| 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 |
Parameters
kx |
horizontal skew factor |
ky |
vertical skew factor |
Example
See Also
postConcat
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:
| J K L | | A B C |
Matrix = | M N O |, other = | D E F |
| P Q R | | G H I |
sets Matrix to:
| 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 |
Parameters
other |
Matrix on left side of multiply expression |
Example
See Also
Enum SkMatrix::ScaleToFit
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.
Constants
| Const | Value | Description |
|---|---|---|
SkMatrix::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. |
SkMatrix::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. |
SkMatrix::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. |
SkMatrix::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
See Also
setRectToRect MakeRectToRect setPolyToPoly
setRectToRect
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:
| 0 0 0 | | 0 0 0 | | 0 0 1 |
Parameters
src |
Rect to map from |
dst |
Rect to map to |
stf |
one of: kFill ScaleToFit, kStart ScaleToFit, kCenter ScaleToFit, kEnd ScaleToFit |
Return Value
true if Matrix can represent Rect mapping
Example
Example Output
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]
See Also
MakeRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
MakeRectToRect
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:
| 0 0 0 | | 0 0 0 | | 0 0 1 |
Parameters
src |
Rect to map from |
dst |
Rect to map to |
stf |
one of: kFill ScaleToFit, kStart ScaleToFit, kCenter ScaleToFit, kEnd ScaleToFit |
Return Value
Example
Example Output
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]
See Also
setRectToRect ScaleToFit setPolyToPoly SkRect::isEmpty
setPolyToPoly
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.
Parameters
src |
Points to map from |
dst |
Points to map to |
count |
number of Points in src and dst |
Return Value
true if Matrix was constructed successfully
Example
See Also
invert
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.
Parameters
inverse |
storage for inverted Matrix; may be nullptr |
Return Value
true if Matrix can be inverted
Example
See Also
SetAffineIdentity
static void SetAffineIdentity(SkScalar affine[6])
Fills affine with identity values in column major order. Sets affine to:
| 1 0 0 | | 0 1 0 |
Affine 3x2 matrices in column major order are used by OpenGL and XPS.
Parameters
affine |
storage for 3x2 affine matrix |
Example
Example Output
ScaleX: 1 SkewY: 0 SkewX: 0 ScaleY: 1 TransX: 0 TransY: 0
See Also
asAffine
bool SK_WARN_UNUSED_RESULT asAffine(SkScalar affine[6]) const
Fills affine in column major order. Sets affine to:
| scale-x skew-x translate-x | | skew-y scale-y translate-y |
If Matrix contains perspective, returns false and leaves affine unchanged.
Parameters
affine |
storage for 3x2 affine matrix; may be nullptr |
Return Value
true if Matrix does not contain perspective
Example
Example Output
ScaleX: 2 SkewY: 5 SkewX: 3 ScaleY: 6 TransX: 4 TransY: 7
See Also
setAffine
void setAffine(const SkScalar affine[6])
Sets Matrix to affine values, passed in column major order. Given affine, column, then row, as:
| scale-x skew-x translate-x | | skew-y scale-y translate-y |
Matrix is set, row, then column, to:
| scale-x skew-x translate-x | | skew-y scale-y translate-y | | 0 0 1 |
Parameters
affine |
3x2 affine matrix |
Example
Example Output
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]
See Also
Transform
| Topic | Description |
|---|---|
| mapHomogeneousPoints | maps Point3 array |
| mapPoints | maps Point array |
| mapPoints(SkPoint dst[], const SkPoint src[], int count) const | |
| mapPoints(SkPoint pts[], int count) const | |
| mapRadius | returns mean radius of mapped Circle |
| mapRect | returns bounds of mapped Rect |
| mapRect(SkRect* dst, const SkRect& src) const | |
| mapRect(SkRect* rect) const | |
| mapRect(const SkRect& src) const | |
| mapRectScaleTranslate | returns bounds of mapped Rect |
| mapRectToQuad | maps Rect to Point array |
| mapVector | maps Vector |
| mapVector(SkScalar dx, SkScalar dy, SkVector* result) const | |
| mapVector(SkScalar dx, SkScalar dy) const | |
| mapVectors | maps Vector array |
| mapVectors(SkVector dst[], const SkVector src[], int count) const | |
| mapVectors(SkVector vecs[], int count) const | |
| mapXY | maps Point |
| mapXY(SkScalar x, SkScalar y, SkPoint* result) const | |
| mapXY(SkScalar x, SkScalar y) const |
mapPoints
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:
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
where
for (i = 0; i < count; ++i) {
x = src[i].fX
y = src[i].fY
}
each dst Point is computed as:
|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.
Parameters
dst |
storage for mapped Points |
src |
Points to transform |
count |
number of Points to transform |
Example
See Also
mapXY[2] mapHomogeneousPoints mapVectors[2]
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:
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
where
for (i = 0; i < count; ++i) {
x = pts[i].fX
y = pts[i].fY
}
each resulting pts Point is computed as:
|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
Parameters
pts |
storage for mapped Points |
count |
number of Points to transform |
Example
See Also
mapXY[2] mapHomogeneousPoints mapVectors[2]
mapHomogeneousPoints
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:
| A B C | | x |
Matrix = | D E F |, src = | y |
| G H I | | z |
each resulting dst Point is computed as:
|A B C| |x|
Matrix * src = |D E F| |y| = |Ax+By+Cz Dx+Ey+Fz Gx+Hy+Iz|
|G H I| |z|
Parameters
dst |
storage for mapped Point3 array |
src |
Point3 array to transform |
count |
items in Point3 array to transform |
Example
See Also
mapPoints[2] mapXY[2] mapVectors[2]
mapXY
void mapXY(SkScalar x, SkScalar y, SkPoint* result) const
Maps Point (x, y) to result. Point is mapped by multiplying by Matrix. Given:
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
result is computed as:
|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
Parameters
x |
x-coordinate of Point to map |
y |
y-coordinate of Point to map |
result |
storage for mapped Point |
Example
See Also
SkPoint mapXY(SkScalar x, SkScalar y) const
Returns Point (x, y) multiplied by Matrix. Given:
| A B C | | x |
Matrix = | D E F |, pt = | y |
| G H I | | 1 |
result is computed as:
|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
Parameters
x |
x-coordinate of Point to map |
y |
y-coordinate of Point to map |
Return Value
mapped Point
Example
See Also
mapVectors
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:
| A B 0 | | x |
Matrix = | D E 0 |, src = | y |
| G H I | | 1 |
where
for (i = 0; i < count; ++i) {
x = src[i].fX
y = src[i].fY
}
each dst Vector is computed as:
|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.
Parameters
dst |
storage for mapped Vectors |
src |
Vectors to transform |
count |
number of Vectors to transform |
Example
See Also
mapVector[2] mapPoints[2] mapXY[2]
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:
| A B 0 | | x |
Matrix = | D E 0 |, vec = | y |
| G H I | | 1 |
where
for (i = 0; i < count; ++i) {
x = vecs[i].fX
y = vecs[i].fY
}
each result Vector is computed as:
|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
Parameters
vecs |
Vectors to transform, and storage for mapped Vectors |
count |
number of Vectors to transform |
Example
See Also
mapVector[2] mapPoints[2] mapXY[2]
mapVector
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:
| A B 0 | | dx |
Matrix = | D E 0 |, vec = | dy |
| G H I | | 1 |
each result Vector is computed as:
|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
Parameters
dx |
x-coordinate of Vector to map |
dy |
y-coordinate of Vector to map |
result |
storage for mapped Vector |
Example
See Also
mapVectors[2] mapPoints[2] mapXY[2]
SkVector mapVector(SkScalar dx, SkScalar dy) const
Returns Vector (x, y) multiplied by Matrix, treating Matrix translation as zero. Given:
| A B 0 | | dx |
Matrix = | D E 0 |, vec = | dy |
| G H I | | 1 |
each result Vector is computed as:
|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
Parameters
dx |
x-coordinate of Vector to map |
dy |
y-coordinate of Vector to map |
Return Value
mapped Vector
Example
See Also
mapVectors[2] mapPoints[2] mapXY[2]
mapRect
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.
Parameters
dst |
storage for bounds of mapped Points |
src |
Rect to map |
Return Value
true if dst is equivalent to mapped src
Example
See Also
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.
Parameters
rect |
rectangle to map, and storage for bounds of mapped corners |
Return Value
true if result is equivalent to mapped src
Example
See Also
mapRectScaleTranslate mapPoints[2] rectStaysRect
SkRect mapRect(const SkRect& src) const
Returns bounds of src corners mapped by Matrix.
Parameters
src |
rectangle to map |
Return Value
mapped bounds
Example
See Also
mapRectToQuad mapRectScaleTranslate
mapRectToQuad
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:
| 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:
|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
Parameters
dst |
storage for mapped corner Points |
rect |
Rect to map |
Example
See Also
mapRect[2][3] mapRectScaleTranslate
mapRectScaleTranslate
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.
Parameters
dst |
storage for bounds of mapped Points |
src |
Rect to map |
Example
See Also
mapRect[2][3] mapRectToQuad isScaleTranslate rectStaysRect
mapRadius
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.
Parameters
radius |
Circle size to map |
Return Value
average mapped radius
Example
See Also
isFixedStepInX
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 Value
true if Matrix does not have complex perspective
Example
Example Output
[ 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
See Also
fixedStepInX
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.
Parameters
y |
position of line parallel to x-axis |
Return Value
Vector advance of mapped unit step in x
Example
See Also
cheapEqualTo
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.
Parameters
m |
Matrix to compare |
Return Value
true if m and Matrix are represented by identical bit patterns
Example
Example Output
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
See Also
operator==(const SkMatrix& a, const SkMatrix& b)
operator==
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.
Parameters
a |
Matrix to compare |
b |
Matrix to compare |
Return Value
true if Matrix a and Matrix b are numerically equal
Example
Example Output
identity: a == b a.cheapEqualTo(b): true
See Also
cheapEqualTo operator!=(const SkMatrix& a, const SkMatrix& b)
operator!=
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.
Parameters
a |
Matrix to compare |
b |
Matrix to compare |
Return Value
true if Matrix a and Matrix b are numerically not equal
Example
See Also
cheapEqualTo operator==(const SkMatrix& a, const SkMatrix& b)
Utility
| Topic | Description |
|---|---|
| dirtyMatrixTypeCache | sets internal cache to unknown state |
| dump | sends text representation using floats to standard output |
dump
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
Example Output
[ 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
See Also
getMinScale
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 Value
minimum scale factor
Example
Example Output
matrix.getMinScale() 24
See Also
getMaxScale
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 Value
maximum scale factor
Example
Example Output
matrix.getMaxScale() 42
See Also
getMinMaxScales
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.
Parameters
scaleFactors |
storage for minimum and maximum scale factors |
Return Value
true if scale factors were computed correctly
Example
Example Output
matrix.getMinMaxScales() false 2 2
See Also
decomposeScale
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 successMatrix = scale * Remaining
Parameters
scale |
x and y scaling factors; may be nullptr |
remaining |
Matrix without scaling; may be nullptr |
Return Value
true if scale can be computed
Example
Example Output
[ 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]
See Also
I
static const SkMatrix& I()
Returns reference to const identity Matrix. Returned Matrix is set to:
| 1 0 0 | | 0 1 0 | | 0 0 1 |
Return Value
const identity Matrix
Example
Example Output
m1 == m2
m2 == m3
See Also
InvalidMatrix
static const SkMatrix& InvalidMatrix()
Returns reference to a const Matrix with invalid values. Returned Matrix is set to:
| SK_ScalarMax SK_ScalarMax SK_ScalarMax | | SK_ScalarMax SK_ScalarMax SK_ScalarMax | | SK_ScalarMax SK_ScalarMax SK_ScalarMax |
Return Value
const invalid Matrix
Example
Example Output
scaleX 3.40282e+38
See Also
SeeAlso getType
Concat
static SkMatrix Concat(const SkMatrix& a, const SkMatrix& b)
Returns Matrix a multiplied by Matrix b.
Given:
| A B C | | J K L |
a = | D E F |, b = | M N O |
| G H I | | P Q R |
sets Matrix to:
| 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 |
Parameters
a |
Matrix on left side of multiply expression |
b |
Matrix on right side of multiply expression |
Return Value
Matrix computed from a times b
Example
See Also
dirtyMatrixTypeCache
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
Example Output
with identity matrix: x = 24
after skew x mod: x = 24
after 2nd skew x mod: x = 24
after dirty cache: x = 66
See Also
setScaleTranslate
void setScaleTranslate(SkScalar sx, SkScalar sy, SkScalar tx, SkScalar ty)
Initializes Matrix with scale and translate elements.
| sx 0 tx | | 0 sy ty | | 0 0 1 |
Parameters
sx |
horizontal scale factor to store |
sy |
vertical scale factor to store |
tx |
horizontal translation to store |
ty |
vertical translation to store |
Example
Example Output
[ 1.0000 0.0000 3.0000][ 0.0000 2.0000 4.0000][ 0.0000 0.0000 1.0000]
See Also
setScale[2] preTranslate postTranslate
isFinite
bool isFinite() const
Returns true if all elements of the matrix are finite. Returns false if any element is infinity, or NaN.
Return Value
true if matrix has only finite elements
Example
Example Output
[ 1.0000 0.0000 nan][ 0.0000 1.0000 0.0000][ 0.0000 0.0000 1.0000]
matrix is finite: false
matrix != matrix
See Also
operator==