> You mentioned multiple ways. What did you have in mind? What do you use?
One way, you later indicated yourself, division. Another way is the method I used, a table of values.
The division method your script/program uses does divides every byte by 16, does it not? (I'm not familar with AMOS Basic files.)
The method I used has the math precalculated, and fixed (hardcoded), in the source and "looks up" the 8 bit value in the table and gets the corresponding 4 bit value.
A mixed method, would calculate the table of 16 4 bit values that correspond to the 256 8 bit values, at run time.
> The conversion is pretty simple. I’m surprised one isn’t already available for both linux and windows.
One isn't? (Check the Picture Format thread)
> That would solve everyone’s image woes.
Not everyone's image woes are solved.
> Ok. I went ahead and wrote my own (sorta).
Did you have to learn machine code?