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vwebp/animation: fix background dispose

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buffer the last frame's details to perform DISPOSE_BACKGROUND on the
image's area, rather than the entire canvas.

also fixes transparent backgrounds with animated images

Change-Id: I53e4d70c441e1eeb136f1d01e7c88de4f9ecff53
This commit is contained in:
James Zern 2013-03-23 12:45:11 -07:00
parent 401f7b856f
commit 04c7a2ecf0
1 changed files with 33 additions and 1 deletions
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34
examples/vwebp.c
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@ -62,6 +62,11 @@ static struct {
const WebPDecBuffer* pic;
WebPDemuxer* dmux;
WebPIterator frameiter;
struct {
int width, height;
int x_offset, y_offset;
enum WebPMuxAnimDispose dispose_method;
} prev_frame;
WebPChunkIterator iccp;
} kParams;
@ -287,9 +292,31 @@ static void HandleDisplay(void) {
glRasterPos2f(-1.f + xoff, 1.f - yoff);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_UNPACK_ROW_LENGTH, pic->u.RGBA.stride / 4);
if (iter->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
if (kParams.prev_frame.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
// TODO(later): these offsets and those above should factor in window size.
// they will be incorrect if the window is resized.
// glScissor() takes window coordinates (0,0 at bottom left).
const int window_x = kParams.prev_frame.x_offset;
const int window_y = kParams.canvas_height -
kParams.prev_frame.y_offset -
kParams.prev_frame.height;
glEnable(GL_SCISSOR_TEST);
// Only updated the requested area, not the whole canvas.
glScissor(window_x, window_y,
kParams.prev_frame.width, kParams.prev_frame.height);
glClear(GL_COLOR_BUFFER_BIT); // use clear color
DrawCheckerBoard();
glDisable(GL_SCISSOR_TEST);
}
kParams.prev_frame.width = iter->width;
kParams.prev_frame.height = iter->height;
kParams.prev_frame.x_offset = iter->x_offset;
kParams.prev_frame.y_offset = iter->y_offset;
kParams.prev_frame.dispose_method = iter->dispose_method;
glDrawPixels(pic->width, pic->height,
GL_RGBA, GL_UNSIGNED_BYTE,
(GLvoid*)pic->u.RGBA.rgba);
@ -426,6 +453,11 @@ int main(int argc, char *argv[]) {
printf("Canvas: %d x %d\n", kParams.canvas_width, kParams.canvas_height);
}
kParams.prev_frame.width = kParams.canvas_width;
kParams.prev_frame.height = kParams.canvas_height;
kParams.prev_frame.x_offset = kParams.prev_frame.y_offset = 0;
kParams.prev_frame.dispose_method = WEBP_MUX_DISPOSE_BACKGROUND;
memset(&kParams.iccp, 0, sizeof(kParams.iccp));
kParams.has_color_profile =
!!(WebPDemuxGetI(kParams.dmux, WEBP_FF_FORMAT_FLAGS) & ICCP_FLAG);