diff options
Diffstat (limited to 'xBRZ/src/xbrz_tools.h')
| -rw-r--r-- | xBRZ/src/xbrz_tools.h | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/xBRZ/src/xbrz_tools.h b/xBRZ/src/xbrz_tools.h index 98164678..d6e48c0c 100644 --- a/xBRZ/src/xbrz_tools.h +++ b/xBRZ/src/xbrz_tools.h @@ -87,10 +87,35 @@ void nearestNeighborScale(PixReader srcReader /* (int x, int y, BytePixel& pix) } +inline +unsigned int uintDivRound(unsigned int num, unsigned int den) +{ + assert(den != 0); + return (num + den / 2) / den; +} + + +inline +unsigned char premultiply(unsigned char c, unsigned char alpha) +{ + return static_cast<unsigned char>(uintDivRound(static_cast<unsigned int>(c) * alpha, 255)); + //premultiply/demultiply using int div round is more accurate than int div floor/ceil pair +} + + +inline +unsigned char demultiply(unsigned char c, unsigned char alpha) +{ + return static_cast<unsigned char>(alpha == 0 ? 0 : + std::clamp(uintDivRound(static_cast<unsigned int>(c) * 255, alpha), 0U, 255U)); +} + + +//caveat: treats alpha channel like regular color! => caller needs to pre/de-multiply alpha! template <class PixReader, class PixWriter> -void bilinearScale(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int srcWidth, int srcHeight, - PixWriter trgWriter /* (const BytePixel& pix) */, int trgWidth, int trgHeight, - int yFirst, int yLast) +void bilinearScaleSimple(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int srcWidth, int srcHeight, + PixWriter trgWriter /* (const BytePixel& pix) */, int trgWidth, int trgHeight, + int yFirst, int yLast) { yFirst = std::max(yFirst, 0); yLast = std::min(yLast, trgHeight); @@ -121,7 +146,7 @@ void bilinearScale(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int const double xx1 = x / scaleX - x1; const double x2x = 1 - xx1; - buf[x] = { x1, x2, xx1, x2x }; + buf[x] = {x1, x2, xx1, x2x}; } for (int y = yFirst; y < yLast; ++y) |