[jpollock]

I am really curious about the search algorithm. I love the palette hack, how did you find candidates to then start searching through the possible palettes?

I can sort of think of:

1) Collapse the colours in the palette to the minimum necessary to be seen as "Waldo". The more slack in the gif palette the better - 24bit colour vs 16 colours (or fewer) in the starting image?

2) For each substring in Pi, map the hex value to a colour (or close to the colour) to match the expected image.

3) find best match - how?

How to backtrack though?

Perhaps pin important fragments?

The glasses and chin seem more important?

[jpollock]

Another pass.

We're looking for a substring with the largest number of unique values. If we have unique values, we can paint each value with a colour close enough to the expected value that humans will see them as the same.

Maybe?

[kundor]

Yes, it helps to have more unique values. We want each repeated byte to occur in part of the pattern where a color also repeats.

What I do is search for substrings with the fewest repeated bytes that don't match the target pattern. I prioritize first minimizing conflicts between light (white and tan) vs. dark (black and red). Reducing other conflicts is a tie-breaker.

The featured gif has 79 "mismatched" pixels out of 494, by the black/white metric. I've found candidates with as few as 75, but subjectively I didn't think they looked as good.