Will I still able to get the hue/saturation of an image if the picture is already a grayscale? Can I use the HSV for getting the hue?
MATLAB: How to get the hue/saturation of a grayscale image
grayscale imagehsvhueImage Processing Toolboxsaturation
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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.
You need to pass in a colormap, N-by-3 array with values between 0 and 1, to to the colormap() function, NOT an image. And you should probably also pass in a handles to the axes you want to apply it to, otherwise it will apply that colormap to every axes in the figure window, which is probably not what you want. So in short, you want:
myColorMap = hsv(256); % Create a colormap.
colormap(gca, myColorMap); % Now apply the colormap.
You can also pass the colormap directly into imshow() and skip calling the colormap() function if you want.
See this full demo and study it:
grayImage = imread('cameraman.tif');subplot(3, 1, 1);imshow(grayImage);axis('on', 'image');title('Original Image');subplot(3, 1, 2);% Create a colormap.myColorMap = hsv(256);% Display image with that colormap.
imshow(grayImage, 'Colormap', myColorMap);colorbar;axis('on', 'image');title('Overlay Image');% Or equivalently, using the colormap() function:
subplot(3, 1, 3);% Display image with no colormap.
imshow(grayImage);% Create a colormap.myColorMap = hsv(256);% Now apply the colormap. Pass in the axes or else it will apply the colormap
% to ALL images on the figure, which is probably not what you want.
colormap(gca, myColorMap);colorbar;axis('on', 'image');title('Overlay Image');
Now, if you already have a colormap, and you want to produce an RGB image, like to write to a file on disk rather than just pseudocoloring a displayed image, you want to call ind2rgb()
rgbImage = ind2rgb(grayImage, myColorMap);
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