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.
