How do I convert any image to a 4-color paletted image using the Python Imaging Library?

Question

I have a device that supports 4-color graphics (much like CGA in the old days).

I wanted to use PIL to read the image and convert it using my 4-color palette (of red

Answer 1

John, I found that first link as well, but it didn't directly help me with the problem. It did make me look deeper into quantize though.

I came up with this yesterday before going to bed:

import sys

import PIL
import Image

PALETTE = [
    0,   0,   0,  # black,  00
    0,   255, 0,  # green,  01
    255, 0,   0,  # red,    10
    255, 255, 0,  # yellow, 11
] + [0, ] * 252 * 3

# a palette image to use for quant
pimage = Image.new("P", (1, 1), 0)
pimage.putpalette(PALETTE)

# open the source image
image = Image.open(sys.argv[1])
image = image.convert("RGB")

# quantize it using our palette image
imagep = image.quantize(palette=pimage)

# save
imagep.save('/tmp/cga.png')

TZ.TZIOY, your solution seems to work along the same principles. Kudos, I should have stopped working on it and waited for your reply. Mine is a bit simpler, although definately not more logical than yours. PIL is cumbersome to use. Yours explains what's going on to do it.