MATLAB: Imagesc make all zeros white

imagescMATLAB

I have the following code. The output is a matrix and I want all of the zeros to be displayed as white. How can I do this?

figure (1)
imagesc(testNSE);
title ('Model vs Observations All NSE')
caxis ([0,1])
colormap(jet)
colorbar

Thank you in advance for any help

Best Answer

Set the first row of the colormap, which will represent 0 since you set up caxis to go from 0 to 1, to be [1,1,1];

myColorMap = jet(256);
myColorMap(1,:) = 1;
colormap(myColorMap);
colorbar

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MATLAB: How to display the intensity of 2D image as a colormap

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);

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 display the intensity of 2D image as a colormap

MATLAB: Convert grayscale to RGB

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