device which creates a bitmap and links

[swftools.git] / lib / pdf / FullBitmapOutputDev.cc

diff --git a/lib/pdf/FullBitmapOutputDev.cc b/lib/pdf/FullBitmapOutputDev.cc
index f19fd25..d35956d 100644 (file)
--- a/lib/pdf/FullBitmapOutputDev.cc
+++ b/lib/pdf/FullBitmapOutputDev.cc
@@ -167,11 +167,13 @@ void FullBitmapOutputDev::flushBitmap()
        gfxcolor_t*out = &img->data[y*rangex];
        Guchar*ain = &alpha[(y+ymin)*width+xmin];
        for(x=0;x<rangex;x++) {
-           // blend against a white background
-           out[x].r = (in[x*3+0]*ain[x])/255 + 255-ain[x];
-           out[x].g = (in[x*3+1]*ain[x])/255 + 255-ain[x];
-           out[x].b = (in[x*3+2]*ain[x])/255 + 255-ain[x];
-           out[x].a = 255;//ain[x];
+           /* according to endPage()/compositeBackground() in xpdf/SplashOutputDev.cc, we
+              have to premultiply alpha (mix background and pixel according to the alpha channel).
+           */
+           out[x].r = (in[x*3+0]*ain[x])/255;
+           out[x].g = (in[x*3+1]*ain[x])/255;
+           out[x].b = (in[x*3+2]*ain[x])/255;
+           out[x].a = ain[x];
        }
     }
     /* transform bitmap rectangle to "device space" */
@@ -190,6 +192,9 @@ void FullBitmapOutputDev::flushBitmap()
     dev->fillbitmap(dev, line, img, &m, 0);
     gfxline_free(line);
 
+    memset(rgbdev->getBitmap()->getAlphaPtr(), 0, rgbdev->getBitmap()->getWidth()*rgbdev->getBitmap()->getHeight());
+    memset(rgbdev->getBitmap()->getDataPtr(), 0, rgbdev->getBitmap()->getRowSize()*rgbdev->getBitmap()->getHeight());
+
     free(img->data);img->data=0;free(img);img=0;
 }