Add 'in place' option for the rgb2hed function (and similar)

[hwarden162]

Description:

In functions such as remove_small_holes there is the option to edit the matrix in place, that is to pass in a mask and have the same mask be edited by the function to save memory. I work on very large H-DAB and H&E images and currently I have to try and tile my image and pass it through a tile at a time to try and save memory. If I could run it in place it would resolve this memory issue for me and other people working with these large images.

Many thanks

[stefanv]

We should do that. Are there any other rgb2 functions that can be adjusted to do the same?

[hwarden162]

It would probably be useful to have it on any function in the skimage.color module that converts between color spaces (any that have a 2 in the name). Purely from personal experience rgb2hed and hed2rgb would be useful ones as those images tend to be quite large( the one I'm currently working on is 37632 x 65536 x 3). I don't know much about the uses of the other colour spaces but there are probably ones there that also are used for large images that would find it useful.

[hmaarrfk]

Is an out parameter better than in place? Seems more generic but maybe comes at some performance loss?

[stefanv]

For functions where input and output sizes are the same, and out argument makes sense. You can just use the input array as the output array then. This is the NumPy pattern.

[github-actions]

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