I should have asked--is this a real-time application, i.e. how fast does the display need to be? If it's a one-and-done, then you can just re-map the image...though if your algorithm is outputting spectral density in linear space, are you sure you should be plotting it on a log axis?
On Wednesday, January 25, 2023 at 8:01:19 AM UTC-5 [email protected] wrote: > It would be fairly easy using a vertex shader in vispy...but I don't know > if they've made any progress in integrating that with QUI toolkits... > > -Jim > > On Tuesday, January 24, 2023 at 8:01:35 PM UTC-5 [email protected] wrote: > >> Thanks everyone >> >> This is surprisingly difficult. I played around with matplotlib's >> pcolormesh, and it does work with log scales, but of course it's slow. >> >> I'll have to think about how to "rescale the spectrogram in log-space", >> seems like the best solution, but it's not immediately obvious to me how to >> do that. >> >> >> >> On Tuesday, January 24, 2023 at 8:38:49 AM UTC-7 [email protected] >> wrote: >> Only PlotCurveItem and ScatterPlotItem (maybe a few other GraphicsItems) >> support stretching/repositioning for log mode. None of the suggestions >> here will support stretching out image-like data. In all cases you will >> need to compute the respective coordinates in log-space yourself. >> >> PColorMeahItem and NonUniformImage will effectively do the same thing in >> this case, but with different kinds of input arguments. Easiest would >> likely be to rescale the spectrogram in log-space, but you will no doubt >> lose resolution in higher frequencies. The other solutions will likely >> work better if you want to be able to zoom in/out and don’t want to lose >> the detail/resolution from the spectrogram calculation (but more >> complicated to implement). >> >> On Tue, Jan 24, 2023 at 05:22 [email protected] <[email protected]> >> wrote: >> Sorry, meant to say I had a look at the PColorMeshItem *source code*... >> >> On Tuesday, January 24, 2023 at 8:20:49 AM UTC-5 [email protected] >> wrote: >> I just had a quick look at the PColorMeshItem, and I don't think it deals >> with nonlinear transforms either. >> >> On Monday, January 23, 2023 at 9:16:53 PM UTC-5 Patrick wrote: >> Hi, >> >> I might be wrong, but I don't think ImageItems work with logarithmic >> axes. They are simple a bitmap image that gets drawn over a rectangular >> area, and the QTransform ( >> https://doc.qt.io/qtforpython/PySide6/QtGui/QTransform.html) which is >> applied is a simple affine transform that won't apply logarithmic >> stretching. >> Perhaps you could try rendering with a PColorMeshItem ( >> https://pyqtgraph.readthedocs.io/en/latest/api_reference/graphicsItems/pcolormeshitem.html) >> >> instead? It might be a little more complex and slower to render, but since >> it renders as a series of polygons, I think it may respect the logarithmic >> coordinates. >> >> Patrick >> On Tuesday, 24 January 2023 at 5:44:34 am UTC+10:30 [email protected] >> wrote: >> (pyqtgraph vers 0.13.1) >> >> I have an application that generates a spectrogram. I use scipys >> spectrogram method, and generate the plot with... >> >> my_plotitem = pg.PlotItem() >> >> f, t, Sxx = scipy.signal.spectrogram( data, Fs=fs) >> my_transform = QtGui.QTransform() >> yscale = f[-1]/Sxx.shape[1] >> xscale = t[-1]/Sxx.shape[0] >> my_transform.scale(xscale, yscale) >> >> my_image = pg.ImageItem() >> my_image.setTransform(my_transform) >> >> my_image.setImage(Sxx) >> my_plotitem.addItem(my_image) >> >> my_plotitem.setLogMode(x=False, y=True) >> >> This works great, but I would like to have the y-axis (the frequencies) >> to be a log scale. I tried using the plotitems setLogMode method... but it >> just changes the tick labels (incorrectly) and doesn't change the plot at >> all. the image on the left is with a linear y-axis, the one on the right >> is after setting same image to setLogMode(x=False, y=True). Note that the >> correct range for the y-axis is 0 to 50. >> >> [image: linear.png][image: log.png] >> >> I've searched around and can't find anything. What is the correct way to >> do this? >> >> J >> >> -- >> You received this message because you are subscribed to the Google Groups >> "pyqtgraph" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/pyqtgraph/779632c0-591a-4ce2-96ee-1f003c1ffc69n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/pyqtgraph/779632c0-591a-4ce2-96ee-1f003c1ffc69n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "pyqtgraph" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/pyqtgraph/42f0dc94-e526-4851-afac-709b0a85958fn%40googlegroups.com.
