From d9002dc181c95aa6f3358776420beda226ab2e2a Mon Sep 17 00:00:00 2001 From: Leonardo Hernández Hernández Date: Fri, 14 Jun 2024 13:58:21 -0600 Subject: webp: do alpha pre-multiplication libwebp returns the alpha as-is --- webp.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/webp.c b/webp.c index 1028f6d..2749511 100644 --- a/webp.c +++ b/webp.c @@ -54,6 +54,29 @@ webp_load(FILE *fp, const char *path) format = PIXMAN_x8b8g8r8; stride = stride_for_format_and_width(format, width); + for (uint32_t *abgr = (uint32_t *)image_data; + abgr < (uint32_t *)(image_data + (size_t)width * (size_t)height * 4); + abgr++) { + uint8_t alpha = (*abgr >> 24) & 0xff; + uint8_t red = (*abgr >> 16) & 0xff; + uint8_t green = (*abgr >> 8) & 0xff; + uint8_t blue = (*abgr >> 0) & 0xff; + + if (alpha == 0xff) + continue; + + if (alpha == 0x00) + blue = green = red = 0x00; + else { + blue = blue * alpha / 0xff; + green = green * alpha / 0xff; + red = red * alpha / 0xff; + } + + *abgr = (uint32_t)alpha << 24 | red << 16 | green << 8 | blue; + } + + ok = NULL != (pix = pixman_image_create_bits_no_clear( format, width, height, (uint32_t *)image_data, stride)); -- cgit v1.2.3