Documentation of pcd.datatype 43.9
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Introduction
------------

With the help of the pcd.datatype, your datatype sytem is able to read images
from Photo-CD's.

This datatype is Freeware !
Do with it what you want, as long as you do not remove any files from this archive !


Minumum requirements for pcd.datatype
-------------------------------------

* OS 3.0
* MC68020
* A mounted PIPE: handler !!
* The PCD decoder 'pcdtoppm' in your path (included).
* ixemul.library V39 (not included, V41 or higher is recommended).
* render.library V29 or better (included).


Additionally recommened
-----------------------

* CyberGraphX with picture.datatype V43 for 24-bit images.


Minumum requirements for PCDPrefs
---------------------------------

* OS 3.0
* MC68020
* MUI 3.8


Installation
------------

Simply click on the 'Install' script.
As the pcd.datatype needs an external decoder, you must select a directory that
is in your path to store the decoder !
The installer will not check your configuration !
You MUST store the decoder 'pcdtoppm' somewhere in your path, otherwise the datatype
will hang up in an endless loop !!


How does the pcd.datatype work ?
---------------------------------

The pcd.datatype is to small to be a standalone decoder.
Whenever the superclass detects a PCD image, it opens the pcd.datatype.
This launches the external PCD decoder 'pcdtoppm', which redirects its output
to the PIPE-handler. The datatype simply reads the decoded RGB values from the
PIPE handler and stores them in the bitmap.


Preferences
-----------

Mode:
 -> V43 CGX Mode
    Enables V43 CyberGraphX mode.
    If you do not have the picture.datatype 43.x, the datatype will fall back to V40 mode.
 -> V40 AGA Mode
    Truecolor images will be color reduced for AGA.

Resolution:
The PCD decoder is able to decompress a PCD image to different resolutions.
The default is 768*512.
The two highest resolutions don't make much sense as you need a fast CPU
and lots of memory !

V40 Dithermode:
Enables Floyd-Steinberg dithering (recommended ,1).
Default is 'No dithering' (0).

V40 Depth:
Depth to use for color reducing in AGA modes.
Values are from 3 to 8 (default).

Currently I only support MUI for the preferences.
If you don't have MUI, you also can adjust the preferences very easy.
The ENV-variable 'DataTypes/pcd.prefs' contains the parameter as a DOS-argument
with the template 'MODE/A/N,RESOLUTION/A/N,DITHER/A/N,DEPTH/A/N'.
You can change the settings anytime either by using the 'SetEnv'-command or by
using a text editor.
A GadTools version of the preferences may follow in the near future.


History
-------

01-Dec-97  V43.0
   * First public release

04-Dec-97  V43.1
   * Works under non-CyberGraphX systems too.

03-Mar-98  V43.2
	* Datatype is now able to reduce colors of 24-bit images with the render.library.
   * Added MUI preferences (no GadTools version, I'm too lazy for it).
   * Added NewIcons to the archive.

09-Mar-98  V43.3
   * Preferences' resolution is now a cycle gadget with text.

17-Mar-98  V43.4
   * Improved method handling.

18-Mar-98  V43.5
   * Shortened file size.
   * More error handling.

09-Apr-98  V43.6
   * Added render.library to archive.
   * Ops ! Forgot, that datatypes requires ixemul.library. Sorry !

20-Jul-98  V43.7
   * Included new render.library 29.0.
     PCD-Datatype new requires this new version.

20-Oct-98  V43.9
   * Changed flags in memory allocation, so it can be used with VMM (Virtual Memory Manager).
   * Included source code in C++.
   * Corrected the DOS template for prefs.
   * Improved libinit.


Credits
-------

Timm S. Müller for the render.library.


Author
------

Feel free to contact me for comments, critics or bug reports !

Name:     Achim Stegemann
Email:    astegema@ix.urz.uni-heidelberg.de
Internet: http://www.rzuser.uni-heidelberg.de/~astegema