adapthisteq
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Hi, I am using Matlab built in function "adapthisteq" which apparently implements the CLAHE algorithm. However, I am a bit confused regarding the size of the tiles in the parameters and its influence. When I use tiles {8x8} the algorithm runs faster than that of {256x256}. Normally, when we divide the image into smaller tiles we end up with large number of processed windows which slows down the underlying algorithm like for example the "blockproc" function. It looks like the "adapthisteq" is actually implementing an {8x8} tile size when the user enters {256x256} that is because:
- The final result has a semi-visible grid of roughly the size of {8x8}
- The output on images resembles more to {8x8} implementation of CLAHE in other languages Java, C++.
I hope to hear from you soon.
Cheers. Cheddad
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Answers (1)
Teja Muppirala
on 28 Mar 2011
The 'numtiles' argument in ADAPTHISTEQ refers to the number of tiles to break the entire image into, and not the actual pixel size of each tile itself. For example, if your image size was 800 x 800, then when you say
adapthisteq(I,[8 8])
you are block processing on 100 pixels by 100 pixels sized blocks. Similarly,
adapthisteq(I,[100 100])
would operate on 8 pixels by 8 pixels sized blocks at a time. This takes much longer, since now you have to do 10000 blocks.
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