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Histogram equalization for color images #28

Merged
merged 10 commits into from
Sep 17, 2020
Merged

Histogram equalization for color images #28

merged 10 commits into from
Sep 17, 2020

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Arcadie
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@Arcadie Arcadie commented Aug 22, 2020 •
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This changes the logic of the processing for color images when histogram equalization is selected:

  • perform 98% contrast adjustment
  • colorize image
  • histogram equalization

Everything else should remain the same.

I'm converting the image to Lab, equalizing the histogram for the L value [0..100], and then converting back to RGBA.

Here is the difference between telemetry / histogram with false color

Large image warning: 6MB

telemetry-vs-historgam

@Arcadie Arcadie changed the title Histogram equalization color Histogram equalization for color images Aug 22, 2020
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Arcadie commented Aug 24, 2020

I've finally managed to make the histogram equalization work "in-place", without copying channels around.
This is more in line with the "processing pipeline" without all the re-assignments (let img = do_something(&img)).

I should have marked this as draft when I started, in case you started reviewing it and I still made some changes, sorry about that.

One thing to be aware of are the unsafe blocks in histogram equalization. It's the same algorithm used in imageproc::contrast::equalize_histogram_mut src, but adapted to work with sub-images, as accessing the pixels is done differently.

Equalizing the histogram for the L channel happens in a similar way, but in range [0..100], so vector length is 101.

Please let me know if you have any suggestions or concerns, thanks!

@Arcadie
Cargo audit, remove vulnerable crate imageproc.
7cfa639 
After running `cargo audit`, it turns out `imageproc` crate has a known vulnerability:
https://rustsec.org/advisories/RUSTSEC-2020-0023

Also, we're no longer using anything from this crate.
If we need something in the future, keep an eye on this pull request that
seems to solve the issue by swapping the vulnerable dependency in imageproc
with another crate:
image-rs/imageproc#417

Details:

```
$cargo audit

error: Vulnerable crates found!

ID:       RUSTSEC-2020-0023
Crate:    rulinalg
Version:  0.4.2
Date:     2020-02-11
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0023
Title:    Lifetime boundary for `raw_slice` and `raw_slice_mut` are incorrect
Solution:  No safe upgrade is available!
Dependency tree:
rulinalg 0.4.2
└── imageproc 0.21.0
    └── noaa-apt 1.2.0
```
martinber
martinber approved these changes Sep 4, 2020
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It's OK the way it is, these are some suggestions that I will do if I find time

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Very nice work. Sorry for taking so long. I will be very busy at least another week

@Arcadie
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Arcadie commented Sep 5, 2020

Sorry for taking so long. I will be very busy at least another week

No worries! I've addressed all the issues, thanks for taking the time to look at this!

@martinber martinber merged commit b3733c4 into martinber:master Sep 17, 2020
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Looks good!

@Arcadie Arcadie deleted the histogram-equalization-color branch September 18, 2020 08:34
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@Arcadie @martinber