MATLAB: Colouring in white pixels on an image

bwcolormapcolormapsimagemanipulationpixelsrgbsaturated

I've been given a 64 bit image which is partially saturated, and I need to convert it to 256 bit, then change the colormap so that the saturated pixels can be colored in blue. How do I do this?

Best Answer

Ignoring the 64 bit nonsense (since I think this just means your image came from a 64 bit computer CPU/operating system), you'd do this:

imshow(yourImage);
cMap = gray(256); % Most of the image is grayscale
cMap(256,:) = [0 0 1]; % Last row is blue.
colormap(cMap);
colorbar;

Related Solutions

MATLAB: To display an 8bit image

If you want to zero out the red and blue channels of your RGB image, you can do this:

rgbImage(:, :, [1, 3]) = 0;
imshow(rgbImage);

The reason that it was appearing gray is that the red and blue channels are the same as the green channel. Zeroing them out will make it look green.

Alternatively you can extract the green channel and apply a colormap.

rgbImage = imread('peppers.png'); % Sample image.
greenChannel = rgbImage(:, :, 2); % Extract green channel
z = zeros(256, 1);
ramp = (0:255)' / 255;
cmap = [z, ramp, z];
colormap(cmap);
colorbar;
imshow(greenChannel, cmap);

MATLAB: Increase RGB image saturation.

This is easier in HSV colorspace:

RGB = rand(100, 100, 3);
HSV = rgb2hsv(RGB);
% "20% more" saturation:
HSV(:, :, 2) = HSV(:, :, 2) * 1.2;
% or add:
% HSV(:, :, 2) = HSV(:, :, 2) + 0.2;
HSV(HSV > 1) = 1;  % Limit values
RGB = hsv2rgb(HSV);

Best Answer

Related Solutions

MATLAB: To display an 8bit image

MATLAB: Increase RGB image saturation.

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