To display an image with a colorbar that indicates the range of intensity values, first use the imshow function to display the image in a MATLAB® figure window and then call the colorbar function to add the colorbar to the image.
When you add a colorbar to an axes object that contains an image object, the colorbar indicates the data values that the different colors in the image correspond to.
If you want to add a colorbar to an image displayed in the Image Viewer, select the Print to Figure option from the File menu. The Image Viewer displays the image in a separate figure window to which you can add a colorbar.
Seeing the correspondence between data values and the colors displayed by using a colorbar is especially useful if you are displaying unconventional range data as an image, as described under Displaying Grayscale Images That Have Unconventional Ranges.
In the example below, a grayscale image of class uint8 is filtered, resulting in data that is no longer in the range [0,255].
RGB = imread('saturn.png'); I = rgb2gray(RGB); h = [1 2 1; 0 0 0; -1 -2 -1]; I2 = filter2(h,I); imshow(I2,'DisplayRange',), colorbar