Question

I’m attempting to create a process manager based on QPixmaps. These pixmaps are updated via a timer callback at 20Hz, so it appears like they’re spinning.

Below is a screenshot of my current window.

The pixmap is a 2D array with [20][14] elements. 20 is the amount of time slices, 14 is the process status indicator. I know, there are only 13 displayed here on the screen.

I’m currently using the painter object and composition modes to add QImages together with the following code:

QImage textImage(mapIcon.size(), QImage::Format_ARGB32);
QImage resultImage(mapIcon.size(), QImage::Format_ARGB32);

QPainter textPainter(&textImage);

textPainter.setCompositionMode(QPainter::CompositionMode_Source);
textPainter.fillRect(mapIcon.rect(), Qt::black);
textPainter.setCompositionMode(QPainter::CompositionMode_SourceOver);
textPainter.setFont(QFont("Arial", 8, QFont::Bold));
textPainter.setPen(QPen(Qt::white));
textPainter.drawText(QRectF(0, 0, mapIcon.width(), mapIcon.height()),
    Qt::AlignCenter, name);
textPainter.end();

QPainter resultPainter(&resultImage);
resultPainter.setCompositionMode(QPainter::CompositionMode_Source);
resultPainter.drawImage(0, 0, mapIcon);
resultPainter.setCompositionMode(QPainter::CompositionMode_Exclusion);
resultPainter.drawImage(0, 0, textImage);

resultPainter.setRenderHint(QPainter::SmoothPixmapTransform, true);
resultPainter.setRenderHint(QPainter::HighQualityAntialiasing, true);

runnerIcons[x][y] = QPixmap::fromImage(resultImage);

My question is this: I don’t want the inverted color scheme seen on the green labels, I want that color black. The white on black is ok, but the magenta isn’t my favorite.

Is this possible in Qt? Or maybe ya’ll have some suggestions to alternative solutions?

Thanks in advance.

Answer 1

There are a couple things you can do. You might check out the QPainter::setCompositionMode (mode) method. Maybe one of the other composition modes would be useful to you? Particularly QPainter::CompositionMode_Exclusion or QPainter::RasterOp_SourceXorDestination.

You could also use a complimentary color for the text. Magenta (blue+red) is opposite green on the color wheel. If you made the text magenta, it would probably show up well against both black and green. (I’m not saying it will look great – just that it will show up well.) Or maybe you could make the text 50% gray so that there is contrast in the luminance as well as in the color?

Also, you only have 13 icons, not 14. Not sure if it makes any difference.