MATLAB: How to get a colour image while reconstruction from R,G and B component.

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when i try to reconstruct a colour image of size M x N, and display it using imshow command, i am getting a image in greyscale of size M x 3N. i understand the logic that 3N is because of RGB component. but how can i convert the M x 3N (greyscale image) into M x N (colour image) using matlab?

Kindly help me..!

Best Answer

If the individual color channel images are stitched side-by-side, then extract them and turn them into a 3D color image

leftImage = grayImage(:, 1:N);
middleImage = grayImage(:, N+1:2*N);
rightImage = grayImage(:, 2*N1:3*N);
rgbImage = cat(3, leftImage, middleImage, rightImage);
imshow(rgbImage);

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MATLAB: How to code image types

Try this:

grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
	% It's not really gray scale like we expected - it's color.
	% Use weighted sum of ALL channels to create a gray scale image.
% 	grayImage = rgb2gray(grayImage);
	% ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
	% which in a typical snapshot will be the least noisy channel.
	grayImage = grayImage(:, :, 1); % Take red channel.
end
if max(grayImage(:)) == 1 && length(unique(grayImage(:))) == 2
    % It's binary because it has only two values: 0 and 1
else
    % It's grayscale
end

You can also use isa(grayImage, 'logical') or similar to identify what class it is.

MATLAB: How to convert RGB image to grayscale image

Sounds like homework. You can get the color channels:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);

and then do a weighted average of them.

grayImage = a1 * redChannel + a2 * greenChannel + a3 * blueChannel;

Look up standard weights, or pick your own.

Best Answer

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