auto crop image (need idea or code)

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symmm 2017-4-24

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https://ww2.mathworks.cn/matlabcentral/answers/337016-auto-crop-image-need-idea-or-code

评论： symmm 2017-4-26

Hey. I want to auto crop/trim the attached image. An image for every kanji character should be the solution. thanks for the help.

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Rik 2017-4-24

Unless every pixel is identical for each character, this will be very difficult. If you are in luck, you can simply look for completely white rows to separate the characters.

Image Analyst 2017-4-24

It looks like there is kerning involved, so looking for white columns won't solve the problem.

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Answer 1

Image Analyst 2017-4-24

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https://ww2.mathworks.cn/matlabcentral/answers/337016-auto-crop-image-need-idea-or-code#answer_264296

在 MATLAB Online 中打开

I suggest you look here for published solutions and algorithms that work: http://www.visionbib.com/bibliography/contentschar.html#OCR,%20Document%20Analysis%20and%20Character%20Recognition%20Systems

4.4 Chinese and Kanji Characters
4.4.1 Chinese Characters, Review, Survey, Evaluations
4.4.2 Chinese Characters, Using Stroke and Radical Analysis, Features
4.4.3 Chinese Characters, Japanese Characters, Handwritten
4.4.4 Online Recognition of Chinese Characters
4.4.5 Chinese Character Seals

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Image Analyst 2017-4-25

在 MATLAB Online 中打开

To find lines, I'd find white areas like Rik says:

verticalProfiles = sum(binaryImage, 2);

Then if depends if you want to crop the letters really tight around the black, or if you want to split them down the middle of the white zone between lines. Which is it?

So now that you've got two characters in a line, now you need to specify the two characters in the line despite the fact that there may be many separate blobs. So what you're going to do is to invert the image, so the letters are white, then label then and call regionprops and ask for centroids. If the x coordinate of the centroid is closer to 1, then the blob belongs on the left side, and if it's closer to the number of columns, then it belongs on the right. Here's a start

% For one two-character sub-image...
[labeledImage, numberOfRegions] = bwlabel(~binaryImage);
[rows, columns] = size(binaryImage);
props = regionprops(labeledImage, 'Centroid');
% Make two images for the left and right characters.
leftChar = false(rows, columns);
rightChar = false(rows, columns);
for k = 1 : numberOfRegions
    % Get a binary image of this blob alone.
    thisBlob = ismember(labeledImage, k);
    x = props(k).Centroid(1);
    if x < (columns - x)
        % Blob is closer to the left edge of the image.
        % Blob belongs to the left character.  Add it in.
        leftChar(thisBlob) = true;
    else
        % Blob is closer to the right edge of the image.
        % Blob belongs to the right character.  Add it in.
        rightChar(thisBlob) = true;
    end    
end
subplot(1, 2, 1);
imshow(leftChar);
subplot(1, 2, 2);
imshow(rightChar);

This should be able to handle kerning (where one character invades the bounding box of another character).

Image Analyst 2017-4-25

编辑：Image Analyst 2017-4-26

symmm, just try the attached code and you'll see it gets every character in every row.

symmm 2017-4-26

Thank You!

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Answer 2

symmm 2017-4-25

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bwkanji_1.jpg

Thanks for the help, but i need to solve this without using ocr(school project). I think i didn't explain the problem enough. I need to trim the strip (see red line for example).

So is there a possibility to count the white pixels between the kanji characters. Or maybe search for a box with white pixels (see black box in picture) and find out the center of the box for the x, y coordinate.