diff options
Diffstat (limited to 'src/XPM.cxx')
| -rw-r--r-- | src/XPM.cxx | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/XPM.cxx b/src/XPM.cxx index f95580403..380ae14c4 100644 --- a/src/XPM.cxx +++ b/src/XPM.cxx @@ -264,6 +264,21 @@ void RGBAImage::SetPixel(int x, int y, ColourDesired colour, int alpha) { pixel[3] = static_cast<unsigned char>(alpha); } +// Transform a block of pixels from RGBA to BGRA with premultiplied alpha. +// Used for DrawRGBAImage on some platforms. +void RGBAImage::BGRAFromRGBA(unsigned char *pixelsBGRA, const unsigned char *pixelsRGBA, size_t count) noexcept { + for (size_t i = 0; i < count; i++) { + const unsigned char alpha = pixelsRGBA[3]; + // Input is RGBA, output is BGRA with premultiplied alpha + pixelsBGRA[2] = pixelsRGBA[0] * alpha / 255; + pixelsBGRA[1] = pixelsRGBA[1] * alpha / 255; + pixelsBGRA[0] = pixelsRGBA[2] * alpha / 255; + pixelsBGRA[3] = alpha; + pixelsRGBA += bytesPerPixel; + pixelsBGRA += bytesPerPixel; + } +} + RGBAImageSet::RGBAImageSet() : height(-1), width(-1) { } |