spectrogram questions

[Uwe]

I found what Qcp's color interpoalation corresponds in Qwt ! I only have to call setResampleMode(QwtMatrixRasterData::BilinearInter polation);

IIRC Qcp does not do any interpolation - it is generating the image first and then uses image processing operations offered by QImage( Qt::SmoothTransformation ). This is different to Qwt, that does a resampling ( in this case interpolation ) on the data before creating the image. When the resolution of the screen is below the resolution of the data this makes a difference as you don't lose values when downsampling.

With the QwtMatrixRasterData::BilinearInterpolation I don't have crashes when the spectrogram is extermely zoomed out ! What do you think about that ??!!??

Asking me to speculate does not make much sense - use the debugger and/or sanitizer and you will know the truth. If you have understood the problem and believe, that there is a bug in Qwt - please file a bug report.

Uwe