MATLAB: How to check for a RGB image or Grayscale image before execution

digital image processingimageimage analysisimage processing

how do i check for a RGB image or Grayscale image before execution?

Best Answer

See this snippet where I check if the number of color channels is 1 and then, if it's not, and I wanted a grayscale image instead of an RGB image, I convert it to gray scale:

grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end

Of course you can call the image array anything you want, and check if numberOfColorChannels > 1 or if numberOfColorChannels == 3, or however you want to do it, and then take whatever actions you want to based on knowing how many color channels it has.

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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: Convert grayscale to RGB

Try it like this if you want to pick some color out of the jet colormap:

workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;
% Create a jet colormap
c = 128;
map = jet(c);
pO2value=double(109); % 109 is an arbitrary number out of 1:128
r = ceil(map(pO2value,1)*c)
g = ceil(map(pO2value,2)*c)
b = ceil(map(pO2value,3)*c)
% Now let's do it to a gray scale image.
% Read in a standard MATLAB gray scale demo image.
grayImage = imread('cameraman.tif');
handleToFigure2 = figure;
subplot(2,2,1);
imshow(grayImage);
title('Gray Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Convert the gray image into RGB so we can get it into hsv space.
rgbImage = cat(3, grayImage, grayImage, grayImage);
hsv = rgb2hsv(rgbImage);
% Make the hue plane of the hsv image this same hue
hsvOfThisPixel = rgb2hsv([r g b])
hsv(:, :, 1) = hsvOfThisPixel(1);
% Make the saturation 1 so we'll see color.
% Originally it was zero which meant that the image would be gray.
hsv(:, :, 2) = 1;
% Convert back to rgb space.
singleHueRGBImage = uint8(255*hsv2rgb(hsv));
% Display the new, single hue color image.
subplot(2, 2, 2);
imshow(singleHueRGBImage);
title('New, Single Hue Color Image', 'FontSize', fontSize);
message = sprintf('Done with demo.');
uiwait(msgbox(message));

Best Answer

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MATLAB: How to code image types

MATLAB: Convert grayscale to RGB

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