individual bands of image.py

1. from PIL import Image
2. import numpy as np
3.  
4. im = Image.open('heartbleed.png')
5.  
6. # In this case, it's a 3-band (red, green, blue) image
7. # so we'll unpack the bands into 3 separate 2D arrays.
8. r, g, b = np.array(im).T
9.  
10. # Let's make an alpha (transparency) band based on where blue is < 100
11. a = np.zeros_like(b)
12. a[b < 100] = 255
13.  
14. # Random math... This isn't meant to look good...
15. # Keep in mind that these are unsigned 8-bit integers, and will overflow.
16. # You may want to convert to floats for some calculations.
17. r = (b + g) * 5
18.  
19. # Put things back together and save the result...
20. im = Image.fromarray(np.dstack([item.T for item in (r,g,b,a)]))
21.  
22. im.save('output.png')