Cropping an image with coordinate values

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I have an image with 848*1102 pixels after edge detection, and I want to crop out a part of the image accurately, so I need to use the coordinate values of the top left and bottom right points. How do I get the coordinates of these two points and crop the image?

Accepted Answer

Image Analyst
Image Analyst on 2 Jan 2023
Edited: Image Analyst on 2 Jan 2023
Try this:
grayImage = imread('001.jpg');
[rows, columns, numberOfColorChannels] = size(grayImage)
rows = 962
columns = 1286
numberOfColorChannels = 3
if numberOfColorChannels == 3
grayImage = grayImage(:, :, 2);
subplot(2, 1, 1);
axis('on', 'image')
% Binarize
mask = grayImage > 128;
% Get rid of things touching the border.
mask = imclearborder(mask);
% Label the image
[LabeledImage, numBlobs] = bwlabel(mask);
% Eliminate the outermost blob, which will have a label of 1. Just keep blobs labeled 2 and up.
mask = ismember(LabeledImage, 2:numBlobs);
% Find the corners of the remaining blobs -- the bounding box.
[r, c] = find(mask);
row1 = min(r)
row1 = 424
row2 = max(r)
row2 = 790
col1 = min(c)
col1 = 437
col2 = max(c)
col2 = 542
% Do the cropping
mask = mask(row1:row2, col1:col2, :);
subplot(2, 1, 2);
axis('on', 'image');
Image Analyst
Image Analyst on 4 Jan 2023
Since it's a sphere, and the curved part won't move very much from image to image, I suggestion you just make up a template mask that you can multiply by your image to erase everything outside it. Just take the attached mask and set your gray scale image, or segmented binary image, outside it to zero.
grayImage(~mask) = 0;
That way nothing on the border or any of those spurious reflections will appear after masking.

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More Answers (1)

Get the indices as rows & colm
Sterne_17 on 2 Jan 2023
Hi, can you explain the code of the first step (Get the indices as rows & colm) in more detail? Because I can't get it to run. Thanks!

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