diff options
| -rw-r--r-- | vcl/workben/vcldemo.cxx | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/vcl/workben/vcldemo.cxx b/vcl/workben/vcldemo.cxx index 7ccde7cab3b9..94d549247410 100644 --- a/vcl/workben/vcldemo.cxx +++ b/vcl/workben/vcldemo.cxx @@ -798,16 +798,25 @@ public: // we get the most precision from the largest delta long nInverseAlpha = std::max(nAR, std::max(nAG, nAB)); // (1-a) nInverseAlpha = CLAMP(nInverseAlpha, 0, 255); + long nAlpha = 255 - nInverseAlpha; pMaskAcc->SetPixel(y,x,BitmapColor((sal_Int8)CLAMP(nInverseAlpha,0,255))); // now recover the pixels - long n2R = aColW.GetRed() + aColB.GetRed(); - long n2G = aColW.GetGreen() + aColB.GetGreen(); - long n2B = aColW.GetBlue() + aColB.GetBlue(); + long nR = (aColW.GetRed() + aColB.GetRed() - nInverseAlpha) * 128; + long nG = (aColW.GetGreen() + aColB.GetGreen() - nInverseAlpha) * 128; + long nB = (aColW.GetBlue() + aColB.GetBlue() - nInverseAlpha) * 128; + if (nAlpha == 0) + { // doesn't matter what's behind transparency + nR = nG = nB = 0; + } + else + { + nR /= nAlpha; nG /= nAlpha; nB /= nAlpha; + } pRecAcc->SetPixel(y,x,BitmapColor( - (sal_uInt8)CLAMP((n2R+1)/2-nInverseAlpha,0,255), - (sal_uInt8)CLAMP((n2G+1)/2-nInverseAlpha,0,255), - (sal_uInt8)CLAMP((n2B+1)/2-nInverseAlpha,0,255))); + (sal_uInt8)CLAMP(nR,0,255), + (sal_uInt8)CLAMP(nG,0,255), + (sal_uInt8)CLAMP(nB,0,255))); #undef CLAMP } } |