PPMA_IO is a MATLAB library which can read or write an ASCII PPM (Portable Pixel Map) file, involving 3 NROW by NCOL integer arrays of RGB color information.
There are many graphics programs, such as XV and GIMP, that can display images in this formats, or translate them to other formats such as BMP, GIF, JPEG, MacPaint, X Window, and so on.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
PPMA_IO is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.
PBMA_IO, a MATLAB library which handles the Portable Bit Map format.
PGMA_IO, a MATLAB library which handles the Portable Gray Map format.
You can go up one level to the MATLAB source codes.