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.

Solution 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

Solution 2

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.

Solution 3

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 ?

Comments

[Cosine]

Thank you, that's wonderful. I've always hated the PIL documentation. How do you then convert it back? With image.convert("RGB", palette=Image.ADAPTIVE, colors=5) or something else?

[unutbu]

This is now documented under im.quantize.

[c0dehunter]

@unutbu, im.quantize is deprecated.