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Now that Owen explained the algorithm, I think I implemented it right for

Browse Source 
* gdk-pixbuf/pixops/pixops.c: (pixops_composite_nearest),
	(composite_pixel), (composite_line):
	* gdk-pixbuf/test-gdk-pixbuf.c: (simple_composite_test_one_type):
	Now that Owen explained the algorithm, I think I implemented it
	right for the cases where the destination pixbuf is not opaque.
	The test does seem to confirm it.
This commit is contained in:
Darin Adler 2000-05-05 02:50:24 +00:00
parent 24fa8a64bc
commit 0f038c9e32
3 changed files with 63 additions and 15 deletions
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9
gdk-pixbuf/ChangeLog
View File

@ -1,3 +1,12 @@
2000-05-04 Darin Adler <darin@eazel.com>
* gdk-pixbuf/pixops/pixops.c: (pixops_composite_nearest),
(composite_pixel), (composite_line):
* gdk-pixbuf/test-gdk-pixbuf.c: (simple_composite_test_one_type):
Now that Owen explained the algorithm, I think I implemented it
right for the cases where the destination pixbuf is not opaque.
The test does seem to confirm it.
2000-05-04 Darin Adler <darin@eazel.com>
* gdk-pixbuf/.cvsignore:

66
gdk-pixbuf/pixops/pixops.c
View File

@ -177,10 +177,24 @@ pixops_composite_nearest (guchar *dest_buf,
if (dest_has_alpha)
{
dest[0] = (a0 * src[0] + (0xff - a0) * dest[0]) / 0xff;
dest[1] = (a0 * src[1] + (0xff - a0) * dest[1]) / 0xff;
dest[2] = (a0 * src[2] + (0xff - a0) * dest[2]) / 0xff;
dest[3] = (0xff * a0 + (0xff - a0) * dest[3]) / 0xff;
unsigned int w0 = 0xff * a0;
unsigned int w1 = (0xff - a0) * dest[3];
unsigned int w = w0 + w1;
if (w != 0)
{
dest[0] = (w0 * src[0] + w1 * dest[0]) / w;
dest[1] = (w0 * src[1] + w1 * dest[1]) / w;
dest[2] = (w0 * src[2] + w1 * dest[2]) / w;
dest[3] = w / 0xff;
}
else
{
dest[0] = 0;
dest[1] = 0;
dest[2] = 0;
dest[3] = 0;
}
}
else
{
@ -296,12 +310,24 @@ composite_pixel (guchar *dest, int dest_x, int dest_channels, int dest_has_alpha
{
if (dest_has_alpha)
{
unsigned int w = (0xff0000 - a) * dest[3];
unsigned int w0 = a - (a >> 8);
unsigned int w1 = ((0xff0000 - a) >> 8) * dest[3];
unsigned int w = w0 + w1;
dest[0] = (r + (0xff0000 - a) * dest[0]) / 0xff0000;
dest[1] = (g + (0xff0000 - a) * dest[1]) / 0xff0000;
dest[2] = (b + (0xff0000 - a) * dest[2]) / 0xff0000;
dest[3] = (0xff * a + (0xff0000 - a) * dest[3]) / 0xff0000;
if (w != 0)
{
dest[0] = (r - (r >> 8) + w1 * dest[0]) / w;
dest[1] = (g - (g >> 8) + w1 * dest[1]) / w;
dest[2] = (b - (b >> 8) + w1 * dest[2]) / w;
dest[3] = w / 0xff00;
}
else
{
dest[0] = 0;
dest[1] = 0;
dest[2] = 0;
dest[3] = 0;
}
}
else
{
@ -354,12 +380,24 @@ composite_line (int *weights, int n_x, int n_y,
if (dest_has_alpha)
{
unsigned int w = (0xff0000 - a) * dest[3];
unsigned int w0 = a - (a >> 8);
unsigned int w1 = ((0xff0000 - a) >> 8) * dest[3];
unsigned int w = w0 + w1;
dest[0] = (r + (0xff0000 - a) * dest[0]) / 0xff0000;
dest[1] = (g + (0xff0000 - a) * dest[1]) / 0xff0000;
dest[2] = (b + (0xff0000 - a) * dest[2]) / 0xff0000;
dest[3] = (0xff * a + (0xff0000 - a) * dest[3]) / 0xff0000;
if (w != 0)
{
dest[0] = (r - (r >> 8) + w1 * dest[0]) / w;
dest[1] = (g - (g >> 8) + w1 * dest[1]) / w;
dest[2] = (b - (b >> 8) + w1 * dest[2]) / w;
dest[3] = w / 0xff00;
}
else
{
dest[0] = 0;
dest[1] = 0;
dest[2] = 0;
dest[3] = 0;
}
}
else
{

3
gdk-pixbuf/test-gdk-pixbuf.c
View File

@ -201,7 +201,8 @@ simple_composite_test_one_type (GdkInterpType type)
success &= simple_composite_test_one (type, 0x00000000, TRUE, 0xFF0000FF, TRUE, 0xFF0000FF);
success &= simple_composite_test_one (type, 0x00000000, TRUE, 0x00FF00FF, TRUE, 0x00FF00FF);
success &= simple_composite_test_one (type, 0x00000000, TRUE, 0x0000FFFF, TRUE, 0x0000FFFF);
success &= simple_composite_test_one (type, 0x00FF0080, TRUE, 0xFFFFFF00, TRUE, 0x7FFF7F80);
success &= simple_composite_test_one (type, 0x00FF0080, TRUE, 0xFFFFFF00, TRUE, 0x00FF0080);
success &= simple_composite_test_one (type, 0xFF000080, TRUE, 0x00FF0040, TRUE, 0xCC32009F);
success &= simple_composite_test_one (type, 0xFFFFFFFF, TRUE, 0xFFFFFFFF, TRUE, 0xFFFFFFFF);
return success;