Hello,

i must implement a brightness/contrast filter.

So far I've managed to brighten an image as follows :

Qt Code: 
  1. QImage ConvolutionFilter:: brighten(QImage& source, int factor)
  2. {
  3. 	if (factor < -255 || factor > 255) return source;
  4. 	int red, green, blue;
  5.  
  6. 	/* for ( int y=0; y<source.height(); y++ ) { 
  7.             uchar *p = source.scanLine(y);
  8.             for (int x = 0; x < source.width(); x ++) {
  9. 		red = int((*p++) + factor);
  10. 		red = (red < 0x00) ? 0x00 : (red > 0xff) ? 0xff : red;
  11.                 green = int((*p++)+ factor);
  12. 		green = (green < 0x00) ? 0x00 : (green > 0xff) ? 0xff : green;
  13.                 blue = int((*p++) + factor);
  14. 		blue =  (blue  < 0x00) ? 0x00 : (blue  > 0xff) ? 0xff : blue ;
  15.                 int alpha = int(*p++);
  16.                 QRgb rgbaValue = qRgba(red,green,blue, alpha);
  17. 				source.setPixel(x,y, rgbaValue);
  18. 				}	
  19. 		}*/
  20.  
  21.     int pixels = source.width() * source.height();
  22.     unsigned int *data = (unsigned int *)source.bits();
  23.     for (int i = 0; i < pixels; ++i) {
  24.         red= qRed(data[i])+ factor;
  25. 	red = (red < 0x00) ? 0x00 : (red > 0xff) ? 0xff : red;
  26. 	green= qGreen(data[i])+factor;
  27. 	green = (green < 0x00) ? 0x00 : (green > 0xff) ? 0xff : green;
  28. 	blue= qBlue(data[i])+factor;
  29. 	blue =  (blue  < 0x00) ? 0x00 : (blue  > 0xff) ? 0xff : blue ;
  30.         data[i] = qRgba(red, green, blue, qAlpha(data[i]));
  31.     }
  32.     return source;
  33. }
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But I'm totally stuck with contrast.

I would deeply appreciate if someone could give me some hints how to handle this task.

Regards.