QCustomPlot Discussion and Comments

colormap display error.Return to overview

While analyzing a signal with size 60000x100. i.e. 6 million points the colormap display shows a funny result:
https://photos.app.goo.gl/L0E0mapT4ILh2Znt2
Has anyone seen this problem before? Any recommendations for a fix.

Best regards

Peter

This might be a limitation internal to Qt's QPixmap/QImage classes, when using so large dimensions. I suggest splitting the data up into multiple segments, e.g. ten 6000x100 color maps.
I know this is a bit tedious, but there's no obvious solution other than rewriting the entire QPixmap/QImage classes with this extreme case in mind.

// Of course: do this only after verifying 100% that your data is in order, and not actually the reason for how this looks. It's come up many times before that people suspect a problem in Qt or QCustomPlot and in the end their data input was not what they thought it was.

Thanks for your promptly reply! The first thing I did was check the data being plotted and it seems correct. A funny thing happens when I zoom. In the figures below there are two screenshots before and after zoom. The data seems ok when you just zoom in just a little bit. Once I zoom out the incorrect section at the bottom reappears. I put a tracker on a mouse event and if I hover over this area I get the right values of the data.

before zooming
https://photos.app.goo.gl/B9zngcDaInC9fAb22
after zooming
https://photos.app.goo.gl/lEDbaceEZvFQ3TyN2