Re: JPEG [JFIF, really] compression

[P3D John Ohrt <johrt@xxxxxxx>]

P3D Ol' Three-Eyes wrote:

> The big largely unexplored area for jpeg is the matter of compression engines.
> You could easily make one that did decent compression of cartoons [sudden
> color boundaries instead of gradual changes] or ones that did a decent job
> of compressing side-by-side stereo images.
>
> It's all a small matter of programming....

First, there are optomizing compression engines which have been available for
some time.  The extent of optimization is constrained by the parameter types and
ranges defined in the jpeg spec.

My experrience is that an optimizing engine will at least get you a 10% reduction
in file size over the default much of the time.  (Remember the default may well
be the optimal choice on some occassions.)  Personally, I think the quality may
be a bit better, but I don't know how one would ever measure that!

A couple of things to avoid are borders and titles etc because they force an
overall compromise on parameter selection.  Strictly speaking, it could be argued
that the "pair" of images in a .jps does compromise quality because of the
artificial discontinuity where the images meet.  However the scenes are highly
similar which should give rise to other efficiencies.

So since .jpeg is designed for photo quality images, I think your first step is
to invent a new spec designed for cartoon-like images.

Regards,


--

John Ohrt * Toronto * ON * Canada





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