How to reduce color palette with PIL

Question

I'm not sure how I would go about reducing the color palette of a PIL Image. I would like to reduce an image's palette to the 5 prominent colors found in that image. My overall goal is to do some basic color sampling.

Answer 1

That's easy, just use the undocumented colors argument:

result = image.convert('P', palette=Image.ADAPTIVE, colors=5)

I'm using Image.ADAPTIVE to avoid dithering

Answer 2

The short answer is to use the Image.quantize method. For more info, see: How do I convert any image to a 4-color paletted image using the Python Imaging Library ?

Answer 3

I assume you want to do something more sophisticated than posterize. "Sampling" as you say, will take some finesse, as the 5 most common colors in the image are likely to be similar to one another. Maybe take a look at the 5 most separated peaks in a histogram.