Find Centroid of a rectangular mask

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Bankim Chandra Yadav 2016-7-29

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评论： Bankim Chandra Yadav 2016-9-8

Four coordinates of a rectangle are given. I need to find the centroid of the area enclosed by the polygon.

Either provide the pixel values and coordinate values of all the pixels enclosed by the polygon OR Provide the centroid of the polygon directly. Please help me out.

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Image Analyst 2016-7-29

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You don't need MATLAB for that, but if you insist. Assuming the x coordinates and y coordinates are in separate arrays....

xCentroid = mean(x);
yCentroid = mean(y);

If you want a digital image pixel value, then round to the nearest row and column:

grayLevel = grayImage(round(yCentroid), round(xCentroid));

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Image Analyst 2016-7-29

freehand_masking_demo.m

In MATLAB, that's called the weighted centroid - like a center of mass. That is weighted by the pixel values. The plain centroid is just based on the shape alone (of the binary image) and doesn't care at all about pixel values. To compute the centroid of weighted centroid, get a binary image, for example using poly2mask()), then call regionprops. Attached is a demo. If it answers your question, you can "Accept this answer" and vote for it.