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/9a98022a-ab9b-4469-bbea-c24c4f43316cn%40googlegroups.com.
