hiseq(Image,TestIma​ge,Background)

Performs a smooth histogram equalization on an image, without the missing 'chunks' in common histogram equalizers. Uses local information to rank pixel values and assign new ones. Up to three inputs:
1) Image to be equalized (required)
2) Test image for (1) to be mapped to (optional)
3) A vector of background pixel values to be omitted from equalization (optional)
Some assumptions are made to make the inputs more convenient. i.e. if you do not have a (2), you should be able to only input (1) and (3), without a placeholder for (2), and the program should be able to detect it.
In the event (2) and (3) are not used, the result is an image with a completely flat histogram, with small deviations to account for odd numbers of pixels.

If (2) is used, the resulting image will have an identical histogram to the image in (2). If (2) is not the same size as (1), it is scaled.

If (3) is used, but not (2), the result is a completely flat histogram with the exception of the values in (3) - they retain their original counts in the histogram.

If both (2) and (3) are used, the result is an image with an identical histogram to (2), with the exception of the values in (3) retaining their original counts.

This should work for any number of dimensions. But this is a greyscale-only function. To use this in color you must treat each frame independently.