How to find the pixel information at a point whose coordinates are known ?

Question

Kushal Joshi 2016-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/299430-how-to-find-the-pixel-information-at-a-point-whose-coordinates-are-known

评论： Mahsa khodaee 2017-11-30

I have a set of (x,y) coordinates and I wish to know the values of pixels at each of these points. How do I do that. Normally, finding the coordinates from pixel value is easy using 'find' function in MATLAB. But this problem is exactly inverse of it. I know coordinates and I want to find pixel values

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Answer 1

Azzi Abdelmalek 2016-8-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/299430-how-to-find-the-pixel-information-at-a-point-whose-coordinates-are-known#answer_231588

在 MATLAB Online 中打开

Im=randi(10,4)
x=[1 2 3]
y=[2 3 4]
id=sub2ind(size(Im),x,y)
pixels=Im(id)

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Image Analyst 2016-8-12

在 MATLAB Online 中打开

If x is horizontal, and y is vertical coordinate (as usual), then this should be

id=sub2ind(size(Im), y, x)

since sub2ind() uses row, column, not x,y. So the rows come first, not the columns.

Mahsa khodaee 2017-11-30

Thanks for your answer! I have the same question! your answer with X, Y matrix is fine! how about the time that we have a points file with a specific coordinate system! In this case, we wouldn't have two specific X and Y matrix.

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