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/bc9d9f4f-57a9-40f8-8472-e9bb9990c751n%40googlegroups.com.
