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qt3/examples/canvas/blendshadow.cpp

54 lines
1.2 KiB

#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" );
}