Image Processing Toolbox

Working with Image Data

Images are most commonly stored in MATLAB using the logical, uint8, uint16 and double data types. This section describes how to work with image data in MATLAB. Topics include:

• Reading images into the MATLAB workspace
• Writing images to files, in many standard graphics file formats
• Querying graphics image files for information stored in header fields
• Converting images between image storage classes
• Converting images between graphics file formats

For information about displaying and printing images, see Displaying and Printing Images.

You can also perform many standard MATLAB array manipulations on uint8 and uint16 image data, including:

• Indexing, including logical indexing
• Reshaping, reordering, and concatenating
• Reading from and writing to MAT-files,
• Using relational operators

Certain MATLAB functions, including the find, all, any, conv2, convn, fft2, fftn, and sum functions accept uint8 or uint16 data but return data in double precision format.

The basic MATLAB arithmetic operators, however, do not accept uint8 or uint16 data. For example, if you attempt to add two uint8 images, A and B, you get an error, such as,

• C = A + B
  ??? Function '+' not defined for variables of class 'uint8'.
  

Because these arithmetic operations are an important part of many image-processing operations, the Image Processing Toolbox includes functions that support these operations on uint8 and uint16 data, as well as the other numeric data types. See Image Arithmetic for more information.

Converting Image Types

Reading a Graphics Image