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video: overlay-composition: fix alpha premultiply and unpremultiply

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Fix component offsets for little endian systems.

https://bugzilla.gnome.org/show_bug.cgi?id=668483
This commit is contained in:
Tim-Philipp Müller 2012-03-14 17:46:23 +00:00
parent 027f5bb471
commit 2c4b379470
1 changed files with 22 additions and 8 deletions
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30
gst-libs/gst/video/video-overlay-composition.c
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@ -869,6 +869,19 @@ gst_video_overlay_rectangle_set_render_rectangle (GstVideoOverlayRectangle *
rectangle->render_height = render_height;
}
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
# define ARGB_A 3
# define ARGB_R 2
# define ARGB_G 1
# define ARGB_B 0
#else
# define ARGB_A 0
# define ARGB_R 1
# define ARGB_G 2
# define ARGB_B 3
#endif
/* FIXME: orc-ify */
static void
gst_video_overlay_rectangle_premultiply (GstBlendVideoFormatInfo * info)
{
@ -876,15 +889,16 @@ gst_video_overlay_rectangle_premultiply (GstBlendVideoFormatInfo * info)
for (j = 0; j < info->height; ++j) {
guint8 *line = info->pixels + info->stride[0] * j;
for (i = 0; i < info->width; ++i) {
int a = line[0];
line[1] = line[1] * a / 255;
line[2] = line[2] * a / 255;
line[3] = line[3] * a / 255;
int a = line[ARGB_A];
line[ARGB_R] = line[ARGB_R] * a / 255;
line[ARGB_G] = line[ARGB_G] * a / 255;
line[ARGB_B] = line[ARGB_B] * a / 255;
line += 4;
}
}
}
/* FIXME: orc-ify */
static void
gst_video_overlay_rectangle_unpremultiply (GstBlendVideoFormatInfo * info)
{
@ -892,11 +906,11 @@ gst_video_overlay_rectangle_unpremultiply (GstBlendVideoFormatInfo * info)
for (j = 0; j < info->height; ++j) {
guint8 *line = info->pixels + info->stride[0] * j;
for (i = 0; i < info->width; ++i) {
int a = line[0];
int a = line[ARGB_A];
if (a) {
line[1] = MIN ((line[1] * 255 + a / 2) / a, 255);
line[2] = MIN ((line[2] * 255 + a / 2) / a, 255);
line[3] = MIN ((line[3] * 255 + a / 2) / a, 255);
line[ARGB_R] = MIN ((line[ARGB_R] * 255 + a / 2) / a, 255);
line[ARGB_G] = MIN ((line[ARGB_G] * 255 + a / 2) / a, 255);
line[ARGB_B] = MIN ((line[ARGB_B] * 255 + a / 2) / a, 255);
}
line += 4;
}