How to display an image using given x coordinates(256256) and y coordinates (256256)

Question

Shafali 2017-3-1

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https://ww2.mathworks.cn/matlabcentral/answers/327616-how-to-display-an-image-using-given-x-coordinates-256-256-and-y-coordinates-256-256

编辑： Image Analyst 2019-10-12

I retrieved x and y coordinates of an RGB image (red, green and blue pixels matrices) and performed arithmetic operations on x and y coordinates matrices separately and displayed the new distorted image. In the second step, I performed all the above arithmetic operation in reverse and got the original x and y coordinates matrices separately. Please help me to display the original image using the recovered original x and y coordinates matrices.

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Answer 1

KSSV 2017-3-2

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https://ww2.mathworks.cn/matlabcentral/answers/327616-how-to-display-an-image-using-given-x-coordinates-256-256-and-y-coordinates-256-256#answer_256917

Read about surf, pcolor

If you have a 3D matrix, use imshow.

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Answer 2

Image Analyst 2017-3-2

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So you have x and y coordinates. They will be be in an N by 2 matrix, right? And then you did something to it to somehow alter the x and y coordinates, but it's still an N by 2 matrix, just with new x,y values in it. So are you wanting to take the new x,y coordinates and build a new color image where the pixel at the old x,y location now appears at the new x,y location? If so, simply use a for loop:

for k = 1 : numel(newX)
    newRow = round(newY(k));
    newCol = round(newX(k));
    newRGB(newRow, newCol, :) = originalRGB(oldY(k), oldX(k), :);
end
imshow(newRGB);

If they're in a 256x256 matrix, like you used meshgrid to get them, then you can still use the above code.

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Image Analyst 2017-3-2

You forgot to attach C:\Users\nitin\Documents\MATLAB\tree.png.

Meanwhile I'm attaching my image scrambling demos.

Shafali 2017-3-2

tree.png

Sorry Sir, Please find attached image file.

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Answer 3

Guillaume 2017-3-2

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https://ww2.mathworks.cn/matlabcentral/answers/327616-how-to-display-an-image-using-given-x-coordinates-256-256-and-y-coordinates-256-256#answer_257018

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I believe I showed you how to get the image based on the coordinates in your previous question

scrambledimage = img(sub2ind(size(img), y1+1, x1+1));  %assuming your |x| and |y| are zero based.

You then simply imshow it:

imshow(scrambledimage);

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Shafali 2017-3-2

Sir, got the result.

pic1=sub2ind(size(scrambledimage), newy, newx);

unscrambled(pic) = scrambledimage(pic1); unscrambled=reshape(unscrambled,256,256);

Thanks for your guidance. I am really very thankful.

Partha Biswas 2019-10-11

编辑：Image Analyst 2019-10-12

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Hi Shafali,

I am trying the code below to unscramble. But it's not happening. Could you please help here? also please let me know what is pic in your code. I am using a 128*128 grayscale image.

f1 = floor((3 + 13 * x) / 128);
x1 = mod(3 + 13 * x, 128); 
f2 = floor((5 + 7 * y) / 128);
y1 = mod(5 + 7 * y, 128);
newx = mod(((x1 + (f1 * 128)) - 3) / 13, 129);
newy = mod(((y1 + (f2 * 128)) - 5) / 7, 129);
pic1=sub2ind(size(scrambledimage), newy, newx);
unscrambled(pic) = scrambledimage(pic1);
unscrambled=reshape(unscrambled,128,128);