Qt 4.8: blendshadow.cpp Example File (graphicsview/portedcanvas/blendshadow.cpp)

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# blendshadow.cpp Example File

graphicsview/portedcanvas/blendshadow.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
     ** Contact: http://www.qt-project.org/legal
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
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     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
     **     of its contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
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     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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     #include <qimage.h>
     #include <qcolor.h>

     static inline int blendComponent( int v, int av, int s, int as )
     {
         return as*s + av*v -(av*as*s)/255;
     }

     static inline QRgb blendShade( QRgb v, QRgb s )
     {
         //shadow image is already reduced and blurred
         int as = qAlpha(s);
         int av = qAlpha(v);
         if ( as == 0 || av == 255 )
             return v;

         int a = as + av -(as*av)/255;

         int r = blendComponent( qRed(v),av, qRed(s), as)/a;
         int g = blendComponent( qGreen(v),av, qGreen(s), as)/a;
         int b = blendComponent( qBlue(v),av, qBlue(s), as)/a;

         return qRgba(r,g,b,a);
     }

     int main( int*, char**)
     {
         QImage image( "out.png" );
         image.convertDepth( 32 );
         QImage shade( "outshade.png" );
         shade.convertDepth( 32 );
         int dx = 10;
         int dy = 5;

         int w = image.width();
         int h = image.height();

         QImage img( w+dx, h+dy, 32 );
         img.setAlphaBuffer( TRUE );

         for ( int y = 0; y < h+dy; y++ ) {
             for ( int x = 0; x < w+dx; x++ ) {
                 QRgb sh =  (x<dx||y<dy) ? 0 : shade.pixel( x-dx, y-dy );
                 QRgb pixel = (x<w&y<h) ? image.pixel( x, y ) : 0;
                 img.setPixel( x, y, blendShade( pixel, sh ) );
             }
         }
         img.save("blend.png", "PNG" );
     }