diamond = np.array([[  0,   0,   0,   0, 255,   0,   0,   0,   0],
       [  0,   0,   0, 255,   0, 255,   0,   0,   0],
       [  0,   0, 255,   0,   0,   0, 255,   0,   0],
       [  0, 255,   0,   0,   0,   0,   0, 255,   0],
       [255,   0,   0,   0,   0,   0,   0,   0, 255],
       [  0, 255,   0,   0,   0,   0,   0, 255,   0],
       [  0,   0, 255,   0,   0,   0, 255,   0,   0],
       [  0,   0,   0, 255,   0, 255,   0,   0,   0],
       [  0,   0,   0,   0, 255,   0,   0,   0,   0]], dtype=uint8)

size = 36
my_dpi = mpl.rcParams['figure.dpi']
plt.subplots(figsize=(size/my_dpi, size/my_dpi))
plt.axis('off')
img = Image.fromarray(diamond, 'L')
img.resize((size,size)).save('diamond.ppm')
plt.imshow(img)