Matlab image intensity level adjustment

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Chen Zhang
Chen Zhang 2017-4-29
评论： Image Analyst 2017-4-30

I have a specific question to ask about the intensity adjustment for image processing. I need high constraint value to find small gaps in the image. I used a manual threshold value 0.99 to convert the grayscale image. However, as the illumination on the surface did not distribute evenly, some parts of the image is lost. I used adaptive method, however, the results is similar to a global threshold. Orignial picture:

Red point as intereted area:

Detail in Binary Image:

I0 = imread('1_2.jpg');
[R,C,K] = size(I0);
if K==1
    I1 = I0;
else
    I1 = rgb2gray(I0);
end

%Adjsut image to get a standar binary picture
%Adjust image intensity value
I1 = imadjust(I1,[0.1 0.7],[]);
BW0   = im2bw(I1,0.99);
    figure;
BW0   = bwareaopen(BW0,10000);
%Fill non_crack hole error
BW0   = bwareaopen(1-BW0,500);
BW0   = 1-BW0;
    imshow(BW0);

After this process, only half of the image will be left. I want a whole image with local intensity threshold which can show the same feature as the high-level threshold. What can I do?

Thanks

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回答（1 个）

Image Analyst
Image Analyst 2017-4-29
You need to do a background correction to get rid of any lens shading. I attach a demo.
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Chen Zhang
Chen Zhang 2017-4-30

Not really, the problem is I have 5 different samples, this manual method may not find all the gaps sometime. I want to generate a universal way to find the location in some other image accurately. Here is another image:

This feature may not be that easy to detect.

Image Analyst
Image Analyst 2017-4-30
Why not use a template - a reference image. Take a perfect version and get the perfect binary image. Then take your test image, call imregister() to align it, then binarize and subtract. Any defects will be super bright.

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