diff options
| -rw-r--r-- | CHANGELOG.md | 4 | ||||
| -rw-r--r-- | png.c | 30 |
2 files changed, 31 insertions, 3 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md index d487564..607d8d6 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -11,6 +11,10 @@ ### Deprecated ### Removed ### Fixed + +* Alpha not being applied correctly to PNG images. + + ### Security ### Contributors @@ -68,12 +68,10 @@ png_load(FILE *fp, const char *path) png_set_strip_16(png_ptr); /* "pack" 16-bit colors to 8-bit */ png_set_bgr(png_ptr); - /* pixman expects pre-multiplied alpha */ - //png_set_alpha_mode(png_ptr, PNG_ALPHA_PREMULTIPLIED, 2.2); - /* Tell libpng to expand to RGB(A) when necessary, and tell pixman * whether we have alpha or not */ pixman_format_code_t format; + switch (color_type) { case PNG_COLOR_TYPE_GRAY: case PNG_COLOR_TYPE_GRAY_ALPHA: @@ -125,6 +123,32 @@ png_load(FILE *fp, const char *path) png_read_image(png_ptr, row_pointers); + /* pixman expects pre-multiplied alpha */ + if (format == PIXMAN_x8r8g8b8) { + for (int i = 0; i < height; i++) { + uint32_t *p = (uint32_t *)row_pointers[i]; + for (int j = 0; j < width; j++, p++) { + uint8_t a = (*p >> 24) & 0xff; + uint8_t r = (*p >> 16) & 0xff; + uint8_t g = (*p >> 8) & 0xff; + uint8_t b = (*p >> 0) & 0xff; + + if (a == 0xff) + continue; + + if (a == 0) { + r = g = b = 0; + } else { + r = r * a / 0xff; + g = g * a / 0xff; + b = b * a / 0xff; + } + + *p = (uint32_t)a << 24 | r << 16 | g << 8 | b; + } + } + } + pix = pixman_image_create_bits_no_clear( format, width, height, (uint32_t *)image_data, stride); |