import matplotlib.pyplot as plt w = 4 h = 3 d = 70 plt.figure(figsize=(w, h), dpi=d) x = [[3, 4, 5], [2, 3, 4], [1, 2, 3]] color_map = plt.imshow(x) color_map.set_cmap("Blues_r") plt.colorbar() plt.savefig("out.png")