diff options
Diffstat (limited to 'src/gui/painting/qdrawhelper_p.h')
| -rw-r--r-- | src/gui/painting/qdrawhelper_p.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h index 179900ddd2..2c222b97c2 100644 --- a/src/gui/painting/qdrawhelper_p.h +++ b/src/gui/painting/qdrawhelper_p.h @@ -882,9 +882,25 @@ template<enum QtPixelOrder> inline uint qConvertRgb32ToRgb30(QRgb); template<enum QtPixelOrder> inline QRgb qConvertA2rgb30ToArgb32(uint c); +// A combined unpremultiply and premultiply with new simplified alpha. +// Needed when alpha loses precision relative to other colors during conversion (ARGB32 -> A2RGB30). +template<unsigned int Shift> +inline QRgb qRepremultiply(QRgb p) +{ + const uint alpha = qAlpha(p); + if (alpha == 255 || alpha == 0) + return p; + p = qUnpremultiply(p); + Q_CONSTEXPR uint mult = 255 / (255 >> Shift); + const uint newAlpha = mult * (alpha >> Shift); + p = (p & ~0xff000000) | (newAlpha<<24); + return qPremultiply(p); +} + template<> inline uint qConvertArgb32ToA2rgb30<PixelOrderBGR>(QRgb c) { + c = qRepremultiply<6>(c); return (c & 0xc0000000) | (((c << 22) & 0x3fc00000) | ((c << 14) & 0x00300000)) | (((c << 4) & 0x000ff000) | ((c >> 4) & 0x00000c00)) @@ -894,6 +910,7 @@ inline uint qConvertArgb32ToA2rgb30<PixelOrderBGR>(QRgb c) template<> inline uint qConvertArgb32ToA2rgb30<PixelOrderRGB>(QRgb c) { + c = qRepremultiply<6>(c); return (c & 0xc0000000) | (((c << 6) & 0x3fc00000) | ((c >> 2) & 0x00300000)) | (((c << 4) & 0x000ff000) | ((c >> 4) & 0x00000c00)) |