bool OverlayEffect::draw(ImageOf<PixelRgb>& src2, ImageOf<PixelRgb>& dest2) {
if (needRead) {
readEffectData();
needRead = false;
}
dest2 = src2;
if (img.isValid()) {
for (int x=0; x<dest2.width()&&x<img.width(); x++) {
for (int y=0; y<dest2.height()&&y<img.height(); y++) {
PixelBgra v = img.pixel(x,y);
if (v.a==0) {
dest2(x,y) = PixelRgb(v.r,v.g,v.b);
} else if (v.a>=127) {
// do nothing, leave copied value
} else {
PixelRgb& o = dest2(x,y);
float f = v.a/127.0;
if (f>1) f = 1;
int r = (int)((1-f)*v.r+f*o.r);
int g = (int)((1-f)*v.g+f*o.g);
int b = (int)((1-f)*v.b+f*o.b);
dest2(x,y) = PixelRgb(r,g,b);
}
}
}
}
return true;
}
