[A83] Re: ZPic83 compression


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[A83] Re: ZPic83 compression




>          So you waste a byte on 5 bits? (your example)

Well.. I *did* use the previous example.. and perhaps it was not the best
one..

>          A picture is one huge string of data.  One big horizontal line,
so
> RLE is a good compression technique.  Everything is one big horizontal
line
> if you think about it like that though.  RLE is good enough for monochrome
> pics simply because there are often large areas of black and white and
> because of it's speed/size.

I usually have lots of consolidated areas (read lines) so it is quite
effective.

> David Phillips has written an RLE
> decompression routine that is only about 30 bytes.

mine is quite a bit larger.. :) but then I'm no expert at asm, I always run
out
of registers..

>          Sometimes, a picture will have better compression through
vertical
> RLE, but I have been unable to find a routine for decompressing this.

Isn't that almost as simple as changing the increment mode and a few
constants?

> Paul Marks's Spite Master is a great utility for turning bitmaps (.bmp
files)
> into sprites, RLE or otherwise.  It can be found at
> http://paul248.cjb.net.  Some information on RLE can be found in the
> contests section of http://void.ticalc.org.

That reminds me, I have got to rewrite my bmp2db and bmp2rldb programs
lost them a while ago.. :/

>          Some information on other forms of compression (ZCP [ZShell
> Compressed PIctures] and EZCMP [EZCMP Zshell CoMPression] ) can be found
in
> the Programs-Misc.  section of the same site.
>          After reading all of that stuff maybe I'll go experiment with a
> little compression:)

RLE is as far as I'll go.. :)

/Jens




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