Pyplot imshow colormap not working

Question

I have the following code:

plt.figure(figsize=(15, 20))
min_v = np.min(net_l0)
max_v = np.max(net_l0)
for i in range(8):
    for j in range(4):
        num = i*4 + j
        plt.subplot(8,4, num+1)
        w_filt = net_l0[num, :3]
        w_filt = w_filt.swapaxes(0, 1).swapaxes(1, 2)
        imgplot = plt.imshow(w_filt, vmin=min_v, vmax=max_v, interpolation='none')
        imgplot.set_cmap('gray')
        plt.colorbar()
plt.show()

For some reason, however, the colormap is not applied to the image only to the colorbar? I tried and adding the cmap keyword to the imshow, but still did not work. Any ideas what I'm doing wrong?

Answer 1

Make sure the array you are displaying is actually 2-dimensional. If you (for example) load a grayscale image that actually has three channels, then imshow will happily show you the image, but it won't apply the colormap to it. The picture is "already color", after all.