Represent bitmaps as arrays of tuples

[Ben Lippmeier]

Representing bitmaps as a 3D array isn't ideal because there's no way to perform a map over all the pixels.

With this representation

Array DIM3 Word8

Suppose we want to convert the image to greyscale in a single operation. We'd really need a function like:

map1 :: (Array DIM1 a -> Array DIM1 a) -> Array DIM3 a -> Array DIM3 a

However, that doesn't work because we can't guarantee that the worker function always returns an array of the same length as the original. Because of this we can't guarantee that the result is rectangular.

If instead we had represented bitmaps as

Array DIM2 (Word8, Word8, Word8

Then we could use the original map function and there'd be no problem.