Grayscale Images

A grayscale image (also called gray-scale, gray scale, or gray-level) is a data matrix whose values represent intensities within some range. MATLAB® stores a grayscale image as an individual matrix, with each element of the matrix corresponding to one image pixel. By convention, this documentation uses the variable name I to refer to grayscale images.

The matrix can be of class uint8, uint16, int16, single, or double. While grayscale images are rarely saved with a colormap, MATLAB uses a colormap to display them.

For a matrix of class single or double, using the default grayscale colormap, the intensity 0 represents black and the intensity 1 represents white. For a matrix of type uint8, uint16, or int16, the intensity intmin(class(I)) represents black and the intensity intmax(class(I)) represents white.

The figure below depicts a grayscale image of class double.

Pixel Values in a Grayscale Image Define Gray Levels

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