Plotting Image Data
About Plotting Image Data
Two-dimensional arrays can be displayed as images,
where the array elements determine brightness or color of the images.
For example, the statements
load durer
whos
Name Size Bytes Class
X 648x509 2638656 double array
caption 2x28 112 char array
map 128x3 3072 double array
load the file durer.mat, adding three variables
to the workspace. The matrix X is a 648-by-509
matrix and map is a 128-by-3 matrix that is the
colormap for this image.
MAT-files, such as durer.mat, are binary
files that can be created on one platform and later read by the MATLAB software
on a different platform.
The elements of X are integers between 1
and 128, which serve as indices into the colormap, map.
Then
image(X)
colormap(map)
axis image
reproduces Albrecht Dürer's etching shown in Matrices and Magic Squares. A high-resolution
scan of the magic square in the upper-right corner is available in
another file. Type
load detail
and then use the up arrow key on your keyboard to reexecute
the image, colormap, and axis commands.
The statement
colormap(hot)
adds some 21st century colorization
to the 16th century etching. The function hot generates
a colormap containing shades of reds, oranges, and yellows. Typically,
a given image matrix has a specific colormap associated with it. See
the colormap reference page
for a list of other predefined colormaps.
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Reading and Writing Images
You can read standard image files (TIFF, JPEG, BMP, etc using
the imread function. The type
of data returned by imread depends on the type
of image you are reading.
You can write MATLAB data to a variety of standard image
formats using the imwrite function.
See the MATLAB reference pages for these functions for more information
and examples.
For More Information
See Displaying Bit-Mapped Images in the MATLAB Graphics
documentation for details about MATLAB image processing capabilities. |
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