Matplotlib plot grid as colormap only in specific area of plot

Question

I hope this hasn't been posted before: I should plot the difference in altitude over time with a picture of a mountain. But I should only plot the colormap in a certain area (black line). I get the colormap usind a grid for 2 different years and calculating the difference in altitude.

My result:

plt.imshow(bild1, extent = [-1100,-200, 1500, 2100], cmap = "Greys_r")
plt.imshow(grid_delta, cmap = "jet", vmin = -5, vmax = 17, origin = "lower", extent = [-1100,-200,1500,2100])
plt.colorbar(boundaries = bounds, ticks = bounds)
plt.plot(studienbereich_x, studienbereich_y, "black", label="Studienbereich", linewidth = 2)
plt.xlim(-1100, -200)
plt.ylim(1500, 2100)
plt.savefig("example.png")

This is what I get: https://i.stack.imgur.com/hy5MH.jpg

This is what I should get: https://i.stack.imgur.com/xQdd7.jpg

I also tried figuring out the data points inside the area of need before interpolating the grids but in the end it didn't fit the area very well.

Answer 1

Change your code to following may solve your problem:

fig = plt.imshow(
    grid_delta,
    cmap="jet",
    vmin=-5,
    vmax=17,
    origin="lower",
    extent=[-1100,-200,1500,2100]
)
cbar = plt.colorbar(fig)

Reference: https://matplotlib.org/examples/pylab_examples/colorbar_tick_labelling_demo.html