This Chapter explains how AMOS Professional is capable of taking data saved in Interchangeable File Format (IFF), and transforming it into superb animations. Old hands and less experienced AMOS users alike will discover a new potential for exploiting programming kills.
IFF graphics have already been discussed as sources for screen pictures and Bob images, and you should be familiar with the LOAD IFF and SAVE IFF commands in the relevant Screens and Bobs Chapters. Here is a brief reminder:
LOAD IFF
instruction: load an IFF screen from a disc
Load IFF "filename"
Load IFF "filename",any screen number
E> Flash Off Load Iff"AMOSPro Examples:Logo.Iff"
SAVE IFF
instruction: save an IFF screen
Save Iff "filename"
Save Iff "filename", compression flag
X> Save Iff "My Programs:Iff/Picture_Name.Iff" : Rem Compressed Save Iff "My_Programs:Iff/Picture_Name.Iff",0 : Rem Uncompressed
Remember that the saved IFF data includes any pre-sets such as SCREEN DISPLAY, SCREEN OFFSET, SCREEN HIDE and SCREEN SHOW.
Optimising IFF animation
It is perfectly possible to create high definition "true video" animation on your Amiga with
AMOS Professional. Unfortunately, you are normally restricted by available memory. Smooth
animations need to display at least 24 "frames" (separate still pictures) every second, and every
16-colour, full-screen picture requires about 32k of storage space. This means that you would
need to invest in a lot of expensive memory storage to run a few seconds of animation, or the
memory of an unexpanded Amiga would be exhausted within two seconds! One solution is to
use tiny images, reduce the number of colours and compact these images using the SPACK
command, but the AMOS Professional programmer deserves better than that.
Adapting the "delta-encoding" technique from the latest video research, AMOS Professional is able to optimise IFF data, concentrating on those parts of the image that actually appear to "move", and disregarding the much larger area of the screen that remains more or less the same. So instead of needing to store a long sequence of complete images, only the differences between one image and the next are recorded. This only requires a fraction of the conventional storage space and as a bonus it means that data can be unpacked extremely quickly.