How do I remove the unwanted white part of the grayscale image?

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Sterne_17 2023-1-7

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评论： Sterne_17 2023-1-9

Image.png

I used the camera to collect a series of images from a line laser hitting a small rotating metal ball and processed them accordingly. Now I only want to keep the images that belong to the outline of the blob, I want to remove the other invalid white parts, how can I achieve this? The parts circled by the red pen are the ones I want to remove.

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Image Analyst 2023-1-7

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I already gave you the answer to that in your duplicate question:

https://www.mathworks.com/matlabcentral/answers/1887222-cropping-an-image-with-coordinate-values#comment_2546822

Basically use a mask.

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Image Analyst 2023-1-9

在 MATLAB Online 中打开

This will do it. Just make sure you have a template/mask that covers where the curvature of the ball is supposed to be.

% Read in edge detected image.
grayImage = imread('001.png');
if size(grayImage, 3) > 1
	% Convert from RGB to gray scale.
	grayImage = grayImage(:,:,1);
end
subplot(3, 1, 1);
imshow(grayImage);
title('Original Image', 'FontSize', 20)
% Read in mask template
mask = imread('sterne mask.png') > 0;
subplot(3, 1, 2);
imshow(mask);
title('Mask', 'FontSize', 20)
% Erase image outside mask
grayImage(~mask) = 0;
subplot(3, 1, 3);
imshow(grayImage);
title('Masked Image', 'FontSize', 20)

You can see by using the mask you can erase everything outside the region where you want to operate.

Sterne_17 2023-1-9

Thank you very, very much for your help！

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Walter Roberson 2023-1-7

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移动：Walter Roberson 2023-1-7

dilate the image to join close groups. bwareafilt to keep the largest only. regionprops to find the edge trace. Use that to extract from the un-dilated image. (I was going to suggest bounding box instead of edge trace but bounding box can have problems with accidentally including additional sections from another branch that happen to curve through the same rectangle.)