Ability to assess similarity of images.

[emiln]

It would be great to be able to express flows like: If this region of the screen is similar to this old version of it, perform some command. One measure for similarity could be simple color histograms. Here's my thought on a first version:

Similarity is calculated by:

• Creating 8 buckets for each of red, green, and blue. The first is for values [0 31], the next [32 63] etc.
• For each pixel considered, increment the proper bucket for its red, green, and blue color value.
• Normalize all buckets relative to the number of pixels considered.
• Calculate the absolute differences in normalized buckets values between the two images.
• Sum up the differences.

Note that this means you can save a "fingerprint" of an image by saving its bucket values.

[emiln]

The Robot class has a nice method for getting a portion of the screen, which should work well for getting test data. Having a buffered image, you can do something along the lines of:

(let [dummy (int-array 3)]
  (for [x (range (.getWidth img))
        y (range (.getHeight img))]
    (-> img (.getData) (.getPixel x y dummy))))

to get all the pixels, which are really int arrays with three elements: red, green, and blue.