QPainter CompositionMode or Interactive PseudoColor Mapping

by Martin Fitzpatrick Last updated FAQ
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lee5378 | 2020-07-14 20:44:12 UTC | #1

I have been playing with the 36 QPainter Modes [Composition and RasterOp] in order to achieve an additive paint application. I expected to be able to paint shapes(rectangles) over each other in a fashion that the overlap between two or more rectangles is another color (say bright red) while leaving the non-overlapping part the same (say dull green). The issue is that I expected the rectangle to add pixel values together first then utilize a colormap, colortable, palette to colorize the individual pixels based on intensity. Perhaps CompostionMode is not the technique I should use. How can this be accomplished? I'd like to see the changes as the rectangles are being painted for an interactive application.

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QPainter CompositionMode or Interactive PseudoColor Mapping was written by Martin Fitzpatrick .

Martin Fitzpatrick has been developing Python/Qt apps for 8 years. Building desktop applications to make data-analysis tools more user-friendly, Python was the obvious choice. Starting with Tk, later moving to wxWidgets and finally adopting PyQt.

QPainter CompositionMode or Interactive PseudoColor Mapping was published in faq on (updated ) . Feedback & Corrections welcome in our public issue tracker.