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image: check if A8 image is bilevel when analyzing transparency

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This commit is contained in:
Adrian Johnson 2011-08-05 21:15:21 +09:30
parent dd73fe9262
commit 16bc8d9361
1 changed files with 13 additions and 2 deletions
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15
src/cairo-image-surface.c
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@ -4879,10 +4879,21 @@ _cairo_image_analyze_transparency (cairo_image_surface_t *image)
return image->transparency = CAIRO_IMAGE_IS_OPAQUE;
if ((image->base.content & CAIRO_CONTENT_COLOR) == 0) {
if (image->format == CAIRO_FORMAT_A1)
if (image->format == CAIRO_FORMAT_A1) {
return image->transparency = CAIRO_IMAGE_HAS_BILEVEL_ALPHA;
else
} else if (image->format == CAIRO_FORMAT_A8) {
for (y = 0; y < image->height; y++) {
uint8_t *alpha = (uint8_t *) (image->data + y * image->stride);
for (x = 0; x < image->width; x++, alpha++) {
if (*alpha > 0 && *alpha < 255)
return image->transparency = CAIRO_IMAGE_HAS_ALPHA;
}
}
return image->transparency = CAIRO_IMAGE_HAS_BILEVEL_ALPHA;
} else {
return image->transparency = CAIRO_IMAGE_HAS_ALPHA;
}
}
if (image->format == CAIRO_FORMAT_RGB16_565) {