Images :: Graphics (Getting Started)

Getting Started

Images

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 MATLAB 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 Dürer's etching shown at the beginning of this book. 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 twentieth century colorization to the sixteenth 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.

Reading and Writing Images

You can read standard image files (TIFF, JPEG, BMP, etc.) into MATLAB 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 reference pages for these functions for more information and examples.

For More Information See Displaying Bit-Mapped Images in the MATLAB documentation for information on the image processing capabilities of MATLAB.

Mesh and Surface Plots Printing Graphics