# how to segment hand from an image with non uniform lighting?

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H on 12 Jul 2014
Commented: Image Analyst on 14 Nov 2020
I'm trying to segment the hand from the image but due to the non uniform lighting the result come out like this
the result in uniform lighting
how to solve this problem?

Image Analyst on 12 Jul 2014
Just fix the lighting - it's so simple! It's almost always easier to prevent the problem than to fix it with software and that is definitely the case here.
If you don't want to get the job done in the most sensible, easy, straightforward, and best way (by fixing the illumination), then there are more complicated ways that you can do it, but you have to make some assumptions, like on the size of the hand, or its color, or on the smoothness of the background, or things like that. Some fix you make for one situation might not work for another. Like if you have that picture and then another where the hand is in front of a flesh colored screen, or a screen with a paisley background - those may all take different algorithms.
For what it's worth, I attach a background correction demo.
Image Analyst on 14 Jul 2014
If you know your background is always neutral colored and your hands are not, then you can convert to hsv color space and threshold for reddish pixels. See my demo : http://www.mathworks.com/matlabcentral/fileexchange/28512-simple-color-detection-by-hue

Laila Kazemi on 12 Jul 2014
You need adaptive threshold since the background changes. I have not yet found a good code in matlab for this. you might have to find your own algorithm and code it.
H on 14 Jul 2014
Here I used graythresh(). but I also tried many different levels for the shareholding other than this level but it didn't work. I also used diifferent segmentation techniques and the result is the same. I think the first step should be fixing the illumination.

Prasad Kalane on 14 Jul 2014
% Do some image illumination correction.
background = imopen(I,strel('disk',15));
I = I - backgroundbackground
% level = graythresh(I);
bw = im2bw(I,0.3*level);

Milion Negewo on 14 Nov 2020
background = imopen(I,strel('disk',15));
I = I - backgroundbackground
% level = graythresh(I);
bw = im2bw(I,0.3*level);
Image Analyst on 14 Nov 2020
% Display original image.
subplot(2, 3, 1);
imshow(I);
title('Original Image');
% Convert to gray scale so we can call imopen().
I = rgb2gray(I);
% Display original image.
subplot(2, 3, 2);
imshow(I);
title('Gray Scale Image');
background = imopen(I, strel('disk',15));
% Display image.
subplot(2, 3, 3);
imshow(background);
title('Background Image');
I = mat2gray(double(I) - double(background));
% Display image.
subplot(2, 3, 4);
imshow(I);
title('Background Subtracted Image');
level = graythresh(I);
bw = im2bw(I, 0.3*level);
% Display image.
subplot(2, 3, 5:6);
imshow(bw);
title('Final Binary Image');
The final image doesn't look so good. I think you need to work on it some more.

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