IDOLON uses a specific tagged file format (TFF), which is similar to the tagged image format (TIF). There is a routine pnmtotff infile outfile to transform .ppm files to .tff files. After the conversion each channel is stored in a .dat file. These files are combined by the relevant .tff file. The conversion of nearly any arbitrary image format to a .ppm file can be performed with the xv command, which is available with most UNIX version or with the pbmplus package.
For the follwing demonstrations the image Convergence.gif [1] was first converted to a .ppm file by the command:
giftoppm Convergence.gif > Convergence.ppm
from the pbmplus routines. The command
pnmtotff Convergence.ppm Convergence.tff
produces a file Convergence.tff, which combines three files , Convergence_2.dat and , since the red green and blue channel of the image were stored in the GIF file respectively.