View source for Manipulate image and apply RGB mask

{{Cleanup | reason=Auto-imported from ExpressionEngine.}}

[[Category:Snippets::Misc]]

Small snippet showing how to take a QImage, run through its pixels and modify them based on certain conditions.

Here img is an input image, the application form has 4 checkboxes, which define the component of the color (ARGB) that is to be masked.

<code>
 // img is the input original image
 QRect rect = img->rect();
 QImage *result = new QImage(wd, ht, img->format());
 uint *output=0, *input = 0;
 for (int y = rect.top(); y < rect.bottom(); y+'')
 {
 input = (uint*)img->scanLine(y - rect.top());
 output = (uint*)result->scanLine(y - rect.top());
 for (int x = rect.left(); x < rect.right(); x)
 {
 int col = *input;
 if (col  Qt::transparent || col  Qt::color0)
 {
 *output''+ = *input+'';
 continue;
 }
 QColor qcol = QColor::fromRgba(col);
 if (ui->redBox->checkState()  0) qcol.setRed(0);
            if (ui->greenBox->checkState()  0) qcol.setGreen(0);
 if (ui->blueBox->checkState()  0) qcol.setBlue(0);
            if (ui->alphaBox->checkState()  0) qcol.setAlpha(0);
 *output''+ = qcol.rgba();
 input+'';
 }
 }
 // At this point result will have the modified QImage
</code>

Here is an alternative version which should be quite a bit faster, but is less readable, perhaps:

<code>
 // img is the input original image
 QRect rect = img->rect();
 QImage *result = new QImage(wd, ht, img->format());
 // Mask is suitable for colors in ARGB byte order.
 uint mask = 0;
 if (ui->redBox->checkState() != 0)
 mask = mask | 0x00ff0000;
 if (ui->greenBox->checkState() != 0)
 mask = mask | 0x0000ff00;
 if (ui->blueBox->checkState() != 0)
 mask = mask | 0x000000ff;
 if (ui->alphaBox->checkState() != 0)
 mask = mask | 0xff000000;
 for (int y = rect.top(); y < rect.bottom(); y)
 {
 uint* input = (uint*)img->scanLine(y - rect.top());
 uint* output = (uint*)result->scanLine(y - rect.top());
 for (int x = rect.left(); x < rect.right(); x)
 {
 *output = *input & mask;
 output;
 input''+;
 }
 }
 // At this point result will have the modified QImage