How to change the values of the pixels in an Qimage?

[kid17]

I read an image with:

QString fileName = QFileDialog::getOpenFileName(this,
                                     tr("Open File"), QDir::currentPath());
  if (!fileName.isEmpty()) {
         QImage image(fileName);
 
         imageLabel->setPixmap(QPixmap::fromImage(image));
         scaleFactor = 1.0;
 
         printAct->setEnabled(true);
         fitToWindowAct->setEnabled(true);
         updateActions();
 
         if (!fitToWindowAct->isChecked())
             imageLabel->adjustSize();
  }

QString fileName = QFileDialog::getOpenFileName(this,
                                     tr("Open File"), QDir::currentPath());
  if (!fileName.isEmpty()) {
         QImage image(fileName);

         imageLabel->setPixmap(QPixmap::fromImage(image));
         scaleFactor = 1.0;

         printAct->setEnabled(true);
         fitToWindowAct->setEnabled(true);
         updateActions();

         if (!fitToWindowAct->isChecked())
             imageLabel->adjustSize();
  }

To copy to clipboard, switch view to plain text mode 

Now I want to change the values of the pixels of this image with new values. They are contained in an matrix[][] of int representing the same image equalized with my function.
The range of values in this matrix is 0-255.
I tried with:

for( int i = 0; i < r; i++ )
        for(int j = 0; j < c; j++)
        	image.setPixel(j,i,(uint)matrix[i][j]);

for( int i = 0; i < r; i++ )
        for(int j = 0; j < c; j++)
        	image.setPixel(j,i,(uint)matrix[i][j]);

To copy to clipboard, switch view to plain text mode 

but don't work, infact if I try to view it, I get a white image
Hepl me!!Thanks.