MATLAB: How to find pixel having a specific value and copy those regions to a new matrix

image processing

find pixel having a specific value and copy those regions to a new matrix…

[rows, columns] = find(L == 0);

how to copy to a new matrix

Best Answer

Something like this should get what you ask for:

Img = peaks;
clf
subplot(2,1,1)
imagesc(Img),colorbar
I2 = 0*Img;
Irange = [2 4];
I2(Irange(1)<=Img(:)&Img(:)<=Irange(2)) = Img(Irange(1)<=Img(:)&Img(:)<=Irange(2));
subplot(2,1,2)
imagesc(I2)

HTH

Related Solutions

MATLAB: How to extract pixel data from a RGB / Grayscale image by specifying a region of interest

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

%%Method 1: Sets image to be transparent except the ROI
I = imread('peppers.png');
image(I); axis off;
disp('please selct the Region Of Interest')
ROI = roipoly(I); % select a closed polygon

myImage = findall(gcf,'type','image');
set(myImage,'AlphaData',ROI);

Method 2

I= imread('peppers.png'); 
image(I); axis off;
disp('please selct the Region Of Interest')
ROI = double(roipoly); % select a closed polygon
ROI = uint8(ROI); % since original image was of type uint8
figure
I2 = zeros(size(I)); % create a new image 
I2(:,:,1) = ROI.*I(:,:,1);
I2(:,:,2) = ROI.*I(:,:,2);
I2(:,:,3) = ROI.*I(:,:,3);
image(uint8(I2)); axis off;
%%Method 3: Utilizes the IMCROP functionality
I= imread('peppers.png');
imshow(I);
rect = [290 160 220 165];
I2= imcrop(I,rect);
figure
imshow(I2);

MATLAB: What does this do r = img1(:,:,1); % red channel g = img1(:,:,2); % green b = img1(:,:,3);

That is taking an RGB image, img1, and extracting the red, green, and blue parts and creating 3 2-D matrices: r,g, and b.

An RGB image, sometimes referred to as a truecolor image, is stored in MATLAB as an M-by-N-by-3 data array that defines red, green, and blue color components for each individual pixel. RGB images do not use a palette. The color of each pixel is determined by the combination of the red, green, and blue intensities stored in each color plane at the pixel's location.

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Related Solutions

MATLAB: How to extract pixel data from a RGB / Grayscale image by specifying a region of interest

MATLAB: What does this do r = img1(:,:,1); % red channel g = img1(:,:,2); % green b = img1(:,:,3);

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