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cairooverlay: Pre-multiply and un-premultiply alpha in case of ARGB32

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Cairo expects pre-multiplied alpha, we work on un-premultiplied alpha.

https://bugzilla.gnome.org/show_bug.cgi?id=797091
This commit is contained in:
Sebastian Dröge 2018-09-25 15:34:40 +03:00
parent 9844bdbf7a
commit f1c5a22a7a
1 changed files with 129 additions and 2 deletions
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131
ext/cairo/gstcairooverlay.c
View file

@ -188,6 +188,130 @@ gst_cairo_overlay_set_info (GstVideoFilter * vfilter, GstCaps * in_caps,
return TRUE;
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_premultiply_0 (GstVideoFrame * frame)
{
int i, j;
for (j = 0; j < GST_VIDEO_FRAME_HEIGHT (frame); ++j) {
guint8 *line;
line = GST_VIDEO_FRAME_PLANE_DATA (frame, 0);
line += GST_VIDEO_FRAME_PLANE_STRIDE (frame, 0) * j;
for (i = 0; i < GST_VIDEO_FRAME_WIDTH (frame); ++i) {
int a = line[0];
line[1] = line[1] * a / 255;
line[2] = line[2] * a / 255;
line[3] = line[3] * a / 255;
line += 4;
}
}
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_premultiply_3 (GstVideoFrame * frame)
{
int i, j;
for (j = 0; j < GST_VIDEO_FRAME_HEIGHT (frame); ++j) {
guint8 *line;
line = GST_VIDEO_FRAME_PLANE_DATA (frame, 0);
line += GST_VIDEO_FRAME_PLANE_STRIDE (frame, 0) * j;
for (i = 0; i < GST_VIDEO_FRAME_WIDTH (frame); ++i) {
int a = line[3];
line[0] = line[0] * a / 255;
line[1] = line[1] * a / 255;
line[2] = line[2] * a / 255;
line += 4;
}
}
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_premultiply (GstVideoFrame * frame)
{
gint alpha_offset;
alpha_offset = GST_VIDEO_FRAME_COMP_POFFSET (frame, 3);
switch (alpha_offset) {
case 0:
gst_video_overlay_rectangle_premultiply_0 (frame);
break;
case 3:
gst_video_overlay_rectangle_premultiply_3 (frame);
break;
default:
g_assert_not_reached ();
break;
}
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_unpremultiply_0 (GstVideoFrame * frame)
{
int i, j;
for (j = 0; j < GST_VIDEO_FRAME_HEIGHT (frame); ++j) {
guint8 *line;
line = GST_VIDEO_FRAME_PLANE_DATA (frame, 0);
line += GST_VIDEO_FRAME_PLANE_STRIDE (frame, 0) * j;
for (i = 0; i < GST_VIDEO_FRAME_WIDTH (frame); ++i) {
int a = line[0];
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 += 4;
}
}
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_unpremultiply_3 (GstVideoFrame * frame)
{
int i, j;
for (j = 0; j < GST_VIDEO_FRAME_HEIGHT (frame); ++j) {
guint8 *line;
line = GST_VIDEO_FRAME_PLANE_DATA (frame, 0);
line += GST_VIDEO_FRAME_PLANE_STRIDE (frame, 0) * j;
for (i = 0; i < GST_VIDEO_FRAME_WIDTH (frame); ++i) {
int a = line[3];
if (a) {
line[0] = MIN ((line[0] * 255 + a / 2) / a, 255);
line[1] = MIN ((line[1] * 255 + a / 2) / a, 255);
line[2] = MIN ((line[2] * 255 + a / 2) / a, 255);
}
line += 4;
}
}
}
/* Copy from video-overlay-composition.c */
static void
gst_video_overlay_rectangle_unpremultiply (GstVideoFrame * frame)
{
gint alpha_offset;
alpha_offset = GST_VIDEO_FRAME_COMP_POFFSET (frame, 3);
switch (alpha_offset) {
case 0:
gst_video_overlay_rectangle_unpremultiply_0 (frame);
break;
case 3:
gst_video_overlay_rectangle_unpremultiply_3 (frame);
break;
default:
g_assert_not_reached ();
break;
}
}
static GstFlowReturn
gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
GstVideoFrame * frame)
@ -223,7 +347,9 @@ gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
GST_VIDEO_FRAME_WIDTH (frame), GST_VIDEO_FRAME_HEIGHT (frame));
} else {
/* FIXME: Need to pre-multiply the alpha in case of ARGB32 */
if (format == CAIRO_FORMAT_ARGB32)
gst_video_overlay_rectangle_premultiply (frame);
surface =
cairo_image_surface_create_for_data (GST_VIDEO_FRAME_PLANE_DATA (frame,
0), format, GST_VIDEO_FRAME_WIDTH (frame),
@ -284,7 +410,8 @@ gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
/* TODO: Put as meta on the buffer */
} else {
cairo_surface_destroy (surface);
/* FIXME: Need to un-premultiply the alpha in case of ARGB32 */
if (format == CAIRO_FORMAT_ARGB32)
gst_video_overlay_rectangle_unpremultiply (frame);
}
return GST_FLOW_OK;