Problem of generating 4 sub-images

Question

gg 2013-11-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106058-problem-of-generating-4-sub-images

编辑： Image Analyst 2013-11-15

I want to divide a color image into 4 sub-images which are also needed to be color images. However, I got the wrong images for my implementation. Please help me. Thanks!

    % I= double(imread('2.jpg'));
% [m,n] = size(I);
% 
% r = I(:,:,1); % Get the RED matrix
% g = I(:,:,2); % Get the GREEN matrix
% b = I(:,:,3); % Get the BLUE matrix
% 
% [m,n] = size(r);
% 
% imgr{1} = r(1:m/2, 1:n/2);
% imgr{2} = r(m/2+1:m, 1:n/2);
% imgr{3} = r(1:m/2, n/2+1:n);
% imgr{4}= r(m/2+1:m, n/2+1:n);
% 
% imgg{1} = g(1:m/2, 1:n/2);
% imgg{2} = g(m/2+1:m, 1:n/2);
% imgg{3} = g(1:m/2, n/2+1:n);
% imgg{4}= g(m/2+1:m, n/2+1:n);
% 
% imgb{1} = b(1:m/2, 1:n/2);
% imgb{2} = b(m/2+1:m, 1:n/2);
% imgb{3} = b(1:m/2, n/2+1:n);
% imgb{4}= b(m/2+1:m, n/2+1:n);
% 
% final_image1(:,:,1)= imgr{1};
% final_image1(:,:,2)= imgg{1};
% final_image1(:,:,3)= imgb{1};
% 
% final_image2(:,:,1)= imgr{2};
% final_image2(:,:,2)= imgg{2};
% final_image2(:,:,3)= imgb{2};
% 
% final_image3(:,:,1)= imgr{3};
% final_image3(:,:,2)= imgg{3};
% final_image3(:,:,3)= imgb{3};
% 
% final_image4(:,:,1)= imgr{4};
% final_image4(:,:,2)= imgg{4};
% final_image4(:,:,3)= imgb{4};
% 
% filename = {final_image1,final_image2,final_image3,final_image4};
% q={'a1.bmp','a2.bmp','a3.bmp','a4.bmp'};
% 
% for i=1:4   
%     imwrite(filename{i},q{i},'bmp');
% end

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Answer 1

Simon 2013-11-14

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https://ww2.mathworks.cn/matlabcentral/answers/106058-problem-of-generating-4-sub-images#answer_115158

Hi!

What exactly is going wrong?

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gg 2013-11-15

在 MATLAB Online 中打开

Great, I did this.It works. Thank you, Simon!

      % code
% I= imread('2.jpg');
% [m,n] = size(I);
% 
% r = uint8 (I(:,:,1)); % Get the RED matrix
% g = uint8 (I(:,:,2)); % Get the GREEN matrix
% b = uint8 (I(:,:,3)); % Get the BLUE matrix
% 
% [m,n] = size(r);
% 
% imgr{1} = r(1:m/2, 1:n/2);
% imgr{2} = r(m/2+1:m, 1:n/2);
% imgr{3} = r(1:m/2, n/2+1:n);
% imgr{4}= r(m/2+1:m, n/2+1:n);
% 
% imgg{1} = g(1:m/2, 1:n/2);
% imgg{2} = g(m/2+1:m, 1:n/2);
% imgg{3} = g(1:m/2, n/2+1:n);
% imgg{4}= g(m/2+1:m, n/2+1:n);
% 
% imgb{1} = b(1:m/2, 1:n/2);
% imgb{2} = b(m/2+1:m, 1:n/2);
% imgb{3} = b(1:m/2, n/2+1:n);
% imgb{4}= b(m/2+1:m, n/2+1:n);
% 
% final_image1(:,:,1)= imgr{1};
% final_image1(:,:,2)= imgg{1};
% final_image1(:,:,3)= imgb{1};
% 
% final_image2(:,:,1)= imgr{2};
% final_image2(:,:,2)= imgg{2};
% final_image2(:,:,3)= imgb{2};
% 
% final_image3(:,:,1)= imgr{3};
% final_image3(:,:,2)= imgg{3};
% final_image3(:,:,3)= imgb{3};
% 
% final_image4(:,:,1)= imgr{4};
% final_image4(:,:,2)= imgg{4};
% final_image4(:,:,3)= imgb{4};
% 
% filename = {final_image1,final_image2,final_image3,final_image4};
% q={'a1.bmp','a2.bmp','a3.bmp','a4.bmp'};
% 
% for i=1:4   
%     imwrite(uint8(filename{i}),q{i},'bmp');
% end
    end

Simon 2013-11-15

You do not neccesarily need the "uint8" conversion of "I" upon splitting the image. If "I" was not defined as double before it will automatically be of class uint8 after "imread".

Image Analyst 2013-11-15

编辑：Image Analyst 2013-11-15

Wow, you really like to have a lot of code don't you? You could have done it in far less space simply by using imcrop() as I and David recommended. See demo code that I added in my answer to show you how simple it can be.

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Answer 2

Image Analyst 2013-11-14

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106058-problem-of-generating-4-sub-images#answer_115164

编辑：Image Analyst 2013-11-15

在 MATLAB Online 中打开

test2.m

Why not simply use imcrop() ? It would take far far fewer lines of code.

And when you do n/2, if n is an odd number, you'll get a .5 fraction off the end of the number and that will not let you do 1:n/2, so you need to do

n1 = floor(n/2);
n2 = n1+1;

Then go from 1 to n1 and from n2 to end.

[rows, columns, numberOfColorChannels] = size(rgbImage);
c1 = floor(columns/2); % Middle column
c2 = c1+1;
r1 = floor(rows/2); % Middle row
r2 = r1+1;
upperLeft = imcrop(rgbImage, [1, 1, c1, r1]);
upperRight = imcrop(rgbImage, [c2, 1, c1, r1]);
lowerLeft = imcrop(rgbImage, [1, r2, c1, r1]);
lowerRight = imcrop(rgbImage, [c2, r2, c1, r1]);

See attached for a full blown demo using MATLAB standard demo image.

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Answer 3

David Sanchez 2013-11-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106058-problem-of-generating-4-sub-images#answer_115295

在 MATLAB Online 中打开

I = your_image;
[r c l] = size(I); % image dimensions
r2 = floor(r/2); 
c2 = floor(c/2);
I1 = imcrop(I,[1 r2 1 c2];
I2 = imcrop(I,[r2+1 r 1 c2]);
I3 = imcrop(I,[1 r2 1 c2+1 c]);
I4 = imcrop(I,[r2+1 r c2+1 c]);

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gg 2013-11-15

在 MATLAB Online 中打开

 I have tried it. But there are some mistakes to implement it.
 if true
    % code
% I= imread('2.jpg');
% [m,n] = size(I);
% 
% % I = your_image;
% [r c l] = size(I); % image dimensions
% r2 = floor(r/2); 
% c2 = floor(c/2);
% tempI{1} = imcrop(I,[1 r2 1 c2]);
% tempI{2} = imcrop(I,[r2+1 r 1 c2]);
% tempI{3} = imcrop(I,[1 r2 1 c2+1 c]);
% tempI{4}= imcrop(I,[r2+1 r c2+1 c]);
% q={'a1.bmp','a2.bmp','a3.bmp','a4.bmp'};
% 
% for i=1:4   
%     imwrite(uint8(tempI{i}),q{i},'bmp');
% end
end