Problems working with 8bpp and 24bpp images

[SkripT]

Hi all, I am programming a simple photo editor program in Qt4.1 with winXp. Well, one of the utilities of the editor is to paint with a given color a selected rectangular area of the image. The code to paint this area is as follows:

void FotoEditorFotos::paintRect(const QColor &color, const QRect &rectAPintar)
{
	int xMin = rectAPintar.x();
	int xMax = xMin + rectAPintar.width() - 1;
	int yMin = rectAPintar.y();
	int yMax = yMin + rectAPintar.height() - 1;
 
	if ( !imatge.valid(xMin, yMin) || !imatge.valid(xMax, yMax)) return;
 
	QRgb *pixelsLiniaFoto;
	QRgb valorColor = color.rgb();
 
	for (int j = yMin; j <= yMax; j++)
	{
		pixelsLiniaFoto = ((QRgb *) imatge.scanLine(j)) + xMin;
 
		for (int i = xMin; i <= xMax; i++)
		{
			*pixelsLiniaFoto = valorColor;
			pixelsLiniaFoto++;
		}
	}
 
	update();
}

void FotoEditorFotos::paintRect(const QColor &color, const QRect &rectAPintar)
{
	int xMin = rectAPintar.x();
	int xMax = xMin + rectAPintar.width() - 1;
	int yMin = rectAPintar.y();
	int yMax = yMin + rectAPintar.height() - 1;

	if ( !imatge.valid(xMin, yMin) || !imatge.valid(xMax, yMax)) return;

	QRgb *pixelsLiniaFoto;
	QRgb valorColor = color.rgb();

	for (int j = yMin; j <= yMax; j++)
	{
		pixelsLiniaFoto = ((QRgb *) imatge.scanLine(j)) + xMin;

		for (int i = xMin; i <= xMax; i++)
		{
			*pixelsLiniaFoto = valorColor;
			pixelsLiniaFoto++;
		}
	}

	update();
}

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The photo (imatge) is part of the class. Well the problem with the code above is that only works with images with 24 bits/pixel, but on the images with 8bpp it give me invalid results. The problem, I guess, is the cast to QRgb*. Anybody knows how to solve it? Thanks.