RGB_IO_PRB
  Demonstrate the use of the RGB_IO routines.

RGB_IO_PRB:
  The output file will have a depth of 8.
  No byte_swapping will be performed.
  The file type is run length encoded (RLE).
  X width in pixels is 128.
  Y width in pixels is 128.
  Z depth in pixels is 3.

RGB_IO_PRB: Read the input image data.
Now we write the output file.

RGB_IO_PRB: Wrote the output file.

RGB_IO_PRB:
  Normal end of execution.