## How can I do the histogram equalization?

### Tomas (view profile)

on 10 Nov 2012

Hello

I think that the histogram equalization on the 3 components of a color image has the effect of increasing the contrast in order to facilitate the detection of the region of interest that is darker than the other part of the image. How can I do this using matlab? thanks

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### Aneesh Balaji (view profile)

on 14 Nov 2012

Hey For a color image split into 3 components and perform histeq on each of them and then recombine them.

Tomas

### Tomas (view profile)

on 14 Nov 2012

I used these lines but i got this result

```r=im(:,:,1);
v=im(:,:,2);
b=im(:,:,3);
r1 = histeq(r);
v1 = histeq(v);
b1 = histeq(b);
img = cat(3,r1,v1,b1);
```

http://s12.postimage.org/cqjo80qpp/result.jpg

### Image Analyst (view profile)

on 14 Nov 2012

Using histeq() on individual color channels is not a good method. You will introduce color artifacts which may be severe. You're best off converting to hsv color space, then using histeq() or adapthisteq() on only the v channel, then recombine and transform back to rgb color space.

Image Analyst

### Image Analyst (view profile)

on 15 Nov 2012

Looks like it should be right. Maybe it's some kind of uint8/double conflict. Can you post your image somewhere?

Tomas

### Tomas (view profile)

on 16 Nov 2012

I'm working on a large number of images. I just need to equalize the histogram to facilitate detection of the dark object. this is an example http://s13.postimage.org/99yr0g2p3/image.jpg

Image Analyst

### Image Analyst (view profile)

on 16 Nov 2012

Histogram equalization is not necessary for that purpose. In fact, it's rarely necessary for anything. And it looks like you'd do best with a texture filter, like entropyfilt() or stdfilt(), at least for the one image you posted.

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