How can I extract pixel data from a RGB / Grayscale image by specifying a region of interest?

2 min readMar 2, 2022

I would like to define a region of interest and then count the number of pixels in it, as well as do various calculations on the region. The region of interest (ROI) could be either a rectangle or an irregular shape.

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There are three different ways this can be achieved. The three examples are shown below:

%%Method 1: Sets image to be transparent except the ROII = imread('peppers.png');image(I); axis off;disp('please selct the Region Of Interest')ROI = roipoly(I); % select a closed polygonmyImage = findall(gcf,'type','image');set(myImage,'AlphaData',ROI);

Method 2

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https://www.matlabsolutions.com/resources/how-can-i-extract-pixel-data-from-a-rgb-grayscale-image-by-specifying-a-region-of-interest-.php

NOTE:-

There are three different ways this can be achieved. The three examples are shown below:

%%Method 1: Sets image to be transparent except the ROII = imread('peppers.png');image(I); axis off;disp('please selct the Region Of Interest')ROI = roipoly(I); % select a closed polygonmyImage = findall(gcf,'type','image');set(myImage,'AlphaData',ROI);

Method 2

SEE COMPLETE ANSWER CLICK THE LINK