I love this engineering blog post by Facebook and always wanted to implement this while working at Realtor.com: https://engineering.fb.com/android/the-technology-behind-preview-photos/
I went as far as to begin work on a Ruby gem in my own time which used stb_image to read the source file and use a constant header. However, I never got the images as small as the FB team (200 bytes).
Really though, it was a C library disguised as a native Ruby gem.
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I may pick this project back up if I ever find a use for it and open-source my private GitHub repo that it lives in.
