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# Histogram-based RGB segmentation

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Teshan Rezel on 6 Feb 2020
Commented: Teshan Rezel on 7 Feb 2020
Hi All,
I'm trying to segment an RGB image based on it's histograms; my code is as follows:
%Split into RGB Channels
Red = img(:,:,1);
Green = img(:,:,2);
Blue = img(:,:,3);
%Get histValues for each channel
[yRed, x] = imhist(Red);
[yGreen, x] = imhist(Green);
[yBlue, x] = imhist(Blue);
%Plot them together in one plot
plot(x, yRed, 'Red', x, yGreen, 'Green', x, yBlue, 'Blue');
histRGB = hist([imhist(Red), imhist(Green), imhist(Blue)]);
histMask = img.*uint8(histRGB);
imshow(histMask)
I get the following error when compiling this section: "Array dimensions must match for binary array op." I'm not sure how to fix this, as I'm not well versed in Matlab currently.
Any help will be appreciated!
Thanks

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### Accepted Answer

Subhadeep Koley on 6 Feb 2020
I am not sure about which algorithm you are trying to implement but below is an example of histogram based segmentation using Otsu's method.
clc; close all;
% Read image into the workspace
img = imread('peppers.png');
% Calculate a 255-bin histogram for the image
[counts, ~] = imhist(rgb2gray(img), 255);
% Compute a global threshold using the histogram counts
T = otsuthresh(counts);
% Create a binary image using the computed threshold
BW = imbinarize(rgb2gray(img), T);
% Display the image
figure; imshowpair(img, BW, 'montage');

#### 1 Comment

Teshan Rezel on 7 Feb 2020
Thanks Subhadeep, much appreciated!

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