MATLAB: Can I specify a particular matrix for the colorbar

colormapmappingmatrices

I'd like to create a map using one particular matrix of data (log-transformed), but make the colorbar from a different matrix data (un-transformed). Is this possible? Can I specify for the colorbar to pull info from a matrix that wasn't used for the map?

Best Answer

No, the colorbar represents the colormap in use. For example you can't show a grayscale colorbar while having the image use the "jet" pseudocolor lookup table/colormap. Though you can redefine what the tick marks say. And you can put up an image the same size as the colorbar right where it would go and display any RGB image in there you'd like (for example a colorbar that looks like what you want rather than the color map that is actually being used on the image being displayed.)

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MATLAB: Assigning color to gray image

I'd just use colormap and not mess with contours unless you know what you're doing and what you want. To pseudocolor a grayscale image an leave it as grayscale but display it as colored:

imshow(grayImage);
colormap(jet(256));
colorbar;

To convert a grayscale image into a true color RGB image and display the RGB image instead of the pseudocolored image:

rgbImage = ind2rgb(grayImage, jet(256));
imshow(rgbImage);

You don't use color bars with RGB images.

MATLAB: Could I set the colorbar resolution？

Give a number close to 256, but not more, to your colormap

image(yourImage);  % I would not use pcolor in most situations.
colorMap = jet(256);
colormap(colorMap);   % Apply the colormap
colorbar;   % Show a colorbar "legend"

Any reason why you're using pcolor? Maybe you don't want the last row and column of your image displayed for some strange reason??? Try imshow() or image() instead.

Best Answer

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MATLAB: Assigning color to gray image

MATLAB: Could I set the colorbar resolution？

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