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.

Note    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.

Mesh and Surface Plots

Printing Graphics