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Partially rewrote rotation code due to a potential alignment problem

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@5978 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Guillermo Rodriguez Garcia 2000-02-11 23:11:40 +00:00
parent 7dd7a90614
commit b5c91ac6b3
1 changed files with 101 additions and 76 deletions
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177
src/common/image.cpp
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@ -2679,17 +2679,10 @@ unsigned long wxImage::ComputeHistogram( wxHashTable &h )
* Rotation code by Carlos Moreno
*/
struct wxRotationPixel
{
unsigned char rgb[3];
};
struct wxRotationPoint
{
wxRotationPoint (double _x, double _y) : x(_x), y(_y) {}
wxRotationPoint (const wxPoint & p) : x(p.x), y(p.y) {}
double x, y;
};
// GRG: I've removed wxRotationPoint - we already have wxRealPoint which
// does exactly the same thing. And I also got rid of wxRotationPixel
// bacause of potential problems in architectures where alignment
// is an issue, so I had to rewrite parts of the code.
static const double gs_Epsilon = 1e-10;
@ -2705,34 +2698,31 @@ static inline int wxCint (double x)
// repeating the time-consuming calls to these functions -- sin/cos can
// be computed and stored in the calling function.
inline wxRotationPoint rotated_point (const wxRotationPoint & p, double cos_angle, double sin_angle, const wxRotationPoint & p0)
inline wxRealPoint rotated_point (const wxRealPoint & p, double cos_angle, double sin_angle, const wxRealPoint & p0)
{
return wxRotationPoint (p0.x + (p.x - p0.x) * cos_angle - (p.y - p0.y) * sin_angle,
p0.y + (p.y - p0.y) * cos_angle + (p.x - p0.x) * sin_angle);
return wxRealPoint (p0.x + (p.x - p0.x) * cos_angle - (p.y - p0.y) * sin_angle,
p0.y + (p.y - p0.y) * cos_angle + (p.x - p0.x) * sin_angle);
}
inline wxRotationPoint rotated_point (double x, double y, double cos_angle, double sin_angle, const wxRotationPoint & p0)
inline wxRealPoint rotated_point (double x, double y, double cos_angle, double sin_angle, const wxRealPoint & p0)
{
return rotated_point (wxRotationPoint(x,y), cos_angle, sin_angle, p0);
return rotated_point (wxRealPoint(x,y), cos_angle, sin_angle, p0);
}
wxImage wxImage::Rotate(double angle, const wxPoint & centre_of_rotation, bool interpolating, wxPoint * offset_after_rotation) const
{
const wxImage& img = * this;
int i;
angle = -angle; // screen coordinates are a mirror image of "real" coordinates
// Create pointer-based array to accelerate access to wxImage's data
wxRotationPixel ** data = new wxRotationPixel * [img.GetHeight()];
unsigned char ** data = new unsigned char * [GetHeight()];
data[0] = (wxRotationPixel *) img.GetData();
data[0] = GetData();
for (i = 1; i < img.GetHeight(); i++)
{
data[i] = data[i - 1] + img.GetWidth();
}
for (i = 1; i < GetHeight(); i++)
data[i] = data[i - 1] + (3 * GetWidth());
// pre-compute coefficients for rotation formula
// precompute coefficients for rotation formula
// (sine and cosine of the angle)
const double cos_angle = cos(angle);
const double sin_angle = sin(angle);
@ -2741,16 +2731,15 @@ wxImage wxImage::Rotate(double angle, const wxPoint & centre_of_rotation, bool i
// First, find rectangle that covers the rotated image; to do that,
// rotate the four corners
const wxRotationPoint p0 = centre_of_rotation;
const wxRealPoint p0(centre_of_rotation.x, centre_of_rotation.y);
wxRotationPoint p1 = rotated_point (0, 0, cos_angle, sin_angle, p0);
wxRotationPoint p2 = rotated_point (0, img.GetHeight(), cos_angle, sin_angle, p0);
wxRotationPoint p3 = rotated_point (img.GetWidth(), 0, cos_angle, sin_angle, p0);
wxRotationPoint p4 = rotated_point (img.GetWidth(), img.GetHeight(), cos_angle, sin_angle, p0);
wxRealPoint p1 = rotated_point (0, 0, cos_angle, sin_angle, p0);
wxRealPoint p2 = rotated_point (0, GetHeight(), cos_angle, sin_angle, p0);
wxRealPoint p3 = rotated_point (GetWidth(), 0, cos_angle, sin_angle, p0);
wxRealPoint p4 = rotated_point (GetWidth(), GetHeight(), cos_angle, sin_angle, p0);
int x1 = (int) floor (wxMin (wxMin(p1.x, p2.x), wxMin(p3.x, p4.x)));
int y1 = (int) floor (wxMin (wxMin(p1.y, p2.y), wxMin(p3.y, p4.y)));
int x2 = (int) ceil (wxMax (wxMax(p1.x, p2.x), wxMax(p3.x, p4.x)));
int y2 = (int) ceil (wxMax (wxMax(p1.y, p2.y), wxMax(p3.y, p4.y)));
@ -2761,48 +2750,45 @@ wxImage wxImage::Rotate(double angle, const wxPoint & centre_of_rotation, bool i
*offset_after_rotation = wxPoint (x1, y1);
}
wxRotationPixel ** result_data = new wxRotationPixel * [rotated.GetHeight()];
result_data[0] = (wxRotationPixel *) rotated.GetData();
for (i = 1; i < rotated.GetHeight(); i++)
{
result_data[i] = result_data[i - 1] + rotated.GetWidth();
}
// GRG: The rotated (destination) image is always accessed
// sequentially, so there is no need for a pointer-based
// array here (and in fact it would be slower).
//
unsigned char * dst = rotated.GetData();
// GRG: if the original image has a mask, use its RGB values
// as the blank pixel, else, fall back to default (black).
//
wxRotationPixel blankPixel = {{ 0, 0, 0 }};
unsigned char blank_r = 0;
unsigned char blank_g = 0;
unsigned char blank_b = 0;
if (HasMask())
{
unsigned char r = GetMaskRed();
unsigned char g = GetMaskGreen();
unsigned char b = GetMaskBlue();
rotated.SetMaskColour( r, g, b );
blankPixel.rgb[0] = r;
blankPixel.rgb[1] = g;
blankPixel.rgb[2] = b;
blank_r = GetMaskRed();
blank_g = GetMaskGreen();
blank_b = GetMaskBlue();
rotated.SetMaskColour( blank_r, blank_g, blank_b );
}
// Now, for each point of the rotated image, find where it came from, by
// performing an inverse rotation (a rotation of -angle) and getting the
// pixel at those coordinates
// GRG: I'd suggest to take the (interpolating) test out of the loops
// GRG: I've taken the (interpolating) test out of the loops, so that
// it is done only once, instead of repeating it for each pixel.
int x;
for (x = 0; x < rotated.GetWidth(); x++)
if (interpolating)
{
for (int y = 0; y < rotated.GetHeight(); y++)
{
wxRotationPoint src = rotated_point (x + x1, y + y1, cos_angle, -sin_angle, p0);
if (interpolating)
for (x = 0; x < rotated.GetWidth(); x++)
{
if (0 < src.x && src.x < img.GetWidth() - 1 &&
0 < src.y && src.y < img.GetHeight() - 1)
wxRealPoint src = rotated_point (x + x1, y + y1, cos_angle, -sin_angle, p0);
if (0 < src.x && src.x < GetWidth() - 1 &&
0 < src.y && src.y < GetHeight() - 1)
{
// interpolate using the 4 enclosing grid-points. Those
// points can be obtained using floor and ceiling of the
@ -2815,10 +2801,11 @@ wxImage wxImage::Rotate(double angle, const wxPoint & centre_of_rotation, bool i
// get four points and the distances (square of the distance,
// for efficiency reasons) for the interpolation formula
const wxRotationPixel & v1 = data[y1][x1];
const wxRotationPixel & v2 = data[y1][x2];
const wxRotationPixel & v3 = data[y2][x2];
const wxRotationPixel & v4 = data[y2][x1];
// GRG: Do not calculate the points until they are
// really needed -- this way we can calculate
// just one, instead of four, if d1, d2, d3
// or d4 are < gs_Epsilon
const double d1 = (src.x - x1) * (src.x - x1) + (src.y - y1) * (src.y - y1);
const double d2 = (src.x - x2) * (src.x - x2) + (src.y - y1) * (src.y - y1);
@ -2833,59 +2820,97 @@ wxImage wxImage::Rotate(double angle, const wxPoint & centre_of_rotation, bool i
if (d1 < gs_Epsilon) // d1,d2,d3,d4 are positive -- no need for abs()
{
result_data[y][x] = v1;
unsigned char *p = data[y1] + (3 * x1);
*(dst++) = *(p++);
*(dst++) = *(p++);
*(dst++) = *(p++);
}
else if (d2 < gs_Epsilon)
{
result_data[y][x] = v2;
unsigned char *p = data[y1] + (3 * x2);
*(dst++) = *(p++);
*(dst++) = *(p++);
*(dst++) = *(p++);
}
else if (d3 < gs_Epsilon)
{
result_data[y][x] = v3;
unsigned char *p = data[y2] + (3 * x2);
*(dst++) = *(p++);
*(dst++) = *(p++);
*(dst++) = *(p++);
}
else if (d4 < gs_Epsilon)
{
result_data[y][x] = v4;
unsigned char *p = data[y2] + (3 * x1);
*(dst++) = *(p++);
*(dst++) = *(p++);
*(dst++) = *(p++);
}
else
{
// weights for the weighted average are proportional to the inverse of the distance
unsigned char *v1 = data[y1] + (3 * x1);
unsigned char *v2 = data[y1] + (3 * x2);
unsigned char *v3 = data[y2] + (3 * x2);
unsigned char *v4 = data[y2] + (3 * x1);
const double w1 = 1/d1, w2 = 1/d2, w3 = 1/d3, w4 = 1/d4;
for (int i = 0; i < 3; i++) // repeat calculation for R, G, and B
{
result_data[y][x].rgb[i] =
(unsigned char) ( (w1 * v1.rgb[i] + w2 * v2.rgb[i] +
w3 * v3.rgb[i] + w4 * v4.rgb[i]) /
(w1 + w2 + w3 + w4) );
}
// GRG: Unrolled.
*(dst++) = (unsigned char)
( (w1 * *(v1++) + w2 * *(v2++) +
w3 * *(v3++) + w4 * *(v4++)) /
(w1 + w2 + w3 + w4) );
*(dst++) = (unsigned char)
( (w1 * *(v1++) + w2 * *(v2++) +
w3 * *(v3++) + w4 * *(v4++)) /
(w1 + w2 + w3 + w4) );
*(dst++) = (unsigned char)
( (w1 * *(v1++) + w2 * *(v2++) +
w3 * *(v3++) + w4 * *(v4++)) /
(w1 + w2 + w3 + w4) );
}
}
else
{
result_data[y][x] = blankPixel;
*(dst++) = blank_r;
*(dst++) = blank_g;
*(dst++) = blank_b;
}
}
else
}
}
else // not interpolating
{
for (int y = 0; y < rotated.GetHeight(); y++)
{
for (x = 0; x < rotated.GetWidth(); x++)
{
const int xs = wxCint (src.x); // wxCint performs rounding to the
wxRealPoint src = rotated_point (x + x1, y + y1, cos_angle, -sin_angle, p0);
const int xs = wxCint (src.x); // wxCint rounds to the
const int ys = wxCint (src.y); // closest integer
if (0 <= xs && xs < img.GetWidth() &&
0 <= ys && ys < img.GetHeight())
if (0 <= xs && xs < GetWidth() &&
0 <= ys && ys < GetHeight())
{
result_data[y][x] = data[ys][xs];
unsigned char *p = data[ys] + (3 * xs);
*(dst++) = *(p++);
*(dst++) = *(p++);
*(dst++) = *(p++);
}
else
{
result_data[y][x] = blankPixel;
*(dst++) = blank_r;
*(dst++) = blank_g;
*(dst++) = blank_b;
}
}
}
}
delete [] data;
delete [] result_data;
return rotated;
}