Finally I have finished my final PhotoCD loader for Image-FX! As promised,
its error reporting is much better, I also increased the loading speed so
that its more than twice as fast as the first two releases. I also worked
much harder on this documentation! PCDIFX is based very loosely on Hadmut 
Danisch's HPCDTOPPM, with the following changes and improvements:
 
o It is a Image-FX loader, as opposed to a standalone PhotoCD to PPM converter.
 
o It is much smaller. HPCDTOPPM is 68K; PCD is 16K.
 
o It uses much less memory. HPCDTOPPM allocates memory for an entire
  conversion and, as such, requires over 22 megabytes to convert a
  3072x2048 pixel image. PCDIFX converts an image row by row and uses less
  than 200 kilobytes for even the largest images.
  
o It works! HPCDTOPPM (which inspired this code of mine) has problems in its 
  3072x2048 conversion code which prevents its from functioning. PCDIFX works 
  in every resolution.
  
o A new "resolution" has been added: 3072x2048 LoRes. Full 3072x2048 is now
  called 3072x2048 HiRes; 3072x2048 LoRes uses one less level of luma and 
  chroma correction and results in a little blurryer image. The tradeoff
  here is speed versus accuracy: a 3072x2048 LoRes image loads more than three 
  times faster than the HiRes version. The degradation is not discernable
  except at extremely high magnifications or on ultra-high resolution displays. 
  As such, LoRes is probably sufficient for most applications. Below are all 
  resolutions and my speed tests.
  
  Resolution   Speed 
  ~~~~~~~~~~   ~~~~~
  192 x 128     0:02
  384 x 256     0:06
  768 x 512     0:21
  1536x1024     3:02
  3072x2048Lo   7:34
  3072x2048Hi  25:26 
                        
  (Timings taken on an A3000/25 with substantial use of virtual memory.)
 
Copyright (c) 1993 by Gunnar Niclase. Permission to use and distribute this
software and its documentation for noncommercial use and without fee is hereby 
granted, provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in supporting 
documentation. It is not allowed to sell this software in any way. This 
software is not public domain.
 
Gunnar

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
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[generic]                 1148    2320  49.5% -lh5- 5128 Dec 30  1993 pcdifx.doc
[generic]                 8081   15620  51.7% -lh5- 2ba2 Dec 31  1993 pcd
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 Total         2 files    9229   17940  51.4%            Jan  7  1994