blendshadow.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation (qt-info@nokia.com)
 **
 ** 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
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of Nokia Corporation 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.
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #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" );
 }