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PASJPEG September 18th, 1996
Based on the Independent JPEG Group's free JPEG library rev 6a
Copyright 1996 by NOMSSI NZALI Jacques H. C. <nomssi@physik.tu-chemnitz.de>
[kn&n DES] See "Legal issues" for conditions of distribution and use.
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Introduction
============
PASJPEG is a port of the sixth public release of the Independent JPEG Group's
C source (release 6a of 7-Feb-96) [3], that implements JPEG baseline,
extended-sequential, and progressive compression processes to Turbo
Pascal 7.0 for DOS (TP). The code has been tested under Delphi 2.0 [6],
it can be ported to other Pascal environments, since many compilers try
to be compatible to TP.
JPEG (pronounced "jay-peg") is a standardized familly of algorithms for
compression of continous tone still images. Most JPEG processes are lossy,
the output image is not exactly identical to the input image. However, on
typical photographic images, very good compression levels can be obtained
with no visible change, and remarkably high compression levels are possible
if you can tolerate a low-quality image [1],[2]. The Independent JPEG Group
(IJG) has created a free, portable C library for JPEG compression and
decompression of JPEG images.
The IJG documentation (system architecture, using the IJG JPEG library,
usage and file list) is a must read. The files DEMO.PAS, TEST.PAS, CJPEG.PAS,
DJPEG.PAS and EXAMPLE.PAS demonstrate the usage of the JPEG decompression
and compression library. The RDJPGCOM application shows how to parse a JFIF
file.
File list
=========
A road map to the files in the PASJPEG distribution
readme.txt Introduction, Documentation
Configuration/installation files
jconfig.inc Configuration declarations.
jpeglib.pas JPEG library's exported data and function declarations.
jmorecfg.pas Additional configuration declarations; need not be changed
for a standard installation.
jerror.pas Declares JPEG library's error and trace message codes.
jinclude.pas
jdct.pas Private declarations for forward & reverse DCT subsystems.
These files contain most of the functions intended to be called directly by
an application program:
jcapimin.pas Application program interface: core routines for compression.
jcapistd.pas Application program interface: standard compression.
jdapimin.pas Application program interface: core routines for decompression.
jdapistd.pas Application program interface: standard decompression.
jcomapi.pas Application program interface routines common to compression
and decompression.
jcparam.pas Compression parameter setting helper routines.
jctrans.pas API and library routines for transcoding compression.
jdtrans.pas API and library routines for transcoding decompression.
Compression side of the library:
jcinit.pas Initialization: determines which other modules to use.
jcmaster.pas Master control: setup and inter-pass sequencing logic.
jcmainct.pas Main buffer controller (preprocessor => JPEG compressor).
jcprepct.pas Preprocessor buffer controller.
jccoefct.pas Buffer controller for DCT coefficient buffer.
jccolor.pas Color space conversion.
jcsample.pas Downsampling.
jcdctmgr.pas DCT manager (DCT implementation selection & control).
jfdctint.pas Forward DCT using slow-but-accurate integer method.
jfdctfst.pas Forward DCT using faster, less accurate integer method.
jfdctflt.pas Forward DCT using floating-point arithmetic.
jchuff.pas Huffman entropy coding for sequential JPEG.
jcphuff.pas Huffman entropy coding for progressive JPEG.
jcmarker.pas JPEG marker writing.
jdatadst.pas Data destination manager for stdio output.
Decompression side of the library:
jdmaster.pas Master control: determines which other modules to use.
jdinput.pas Input controller: controls input processing modules.
jdmainct.pas Main buffer controller (JPEG decompressor => postprocessor).
jdcoefct.pas Buffer controller for DCT coefficient buffer.
jdpostct.pas Postprocessor buffer controller.
jdmarker.pas JPEG marker reading.
jdhuff.pas Huffman entropy decoding for sequential JPEG.
jdphuff.pas Huffman entropy decoding for progressive JPEG.
jddctmgr.pas IDCT manager (IDCT implementation selection & control).
jidctint.pas Inverse DCT using slow-but-accurate integer method.
jidctfst.pas Inverse DCT using faster, less accurate integer method.
jidctflt.pas Inverse DCT using floating-point arithmetic.
jidctred.pas Inverse DCTs with reduced-size outputs.
jidct2d.pas Direct 2D Inverse DCT - NOT READY YET
jdsample.pas Upsampling.
jdcolor.pas Color space conversion.
jdmerge.pas Merged upsampling/color conversion (faster, lower quality).
jquant1.pas One-pass color quantization using a fixed-spacing colormap.
jquant2.pas Two-pass color quantization using a custom-generated colormap.
Also handles one-pass quantization to an externally given map.
jdatasrc.pas Data source manager for stdio input.
Support files for both compression and decompression:
jerror.pas Standard error handling routines (application replaceable).
jmemmgr.pas System-independent (more or less) memory management code.
jutils.pas Miscellaneous utility routines.
jmemmgr.pas relies on a system-dependent memory management module. The
PASJPEG distribution includes the following implementations of the system-
dependent module:
jmemnobs.pas "No backing store": assumes adequate virtual memory exists.
jmemdos.pas Custom implementation for MS-DOS: knows about extended and
expanded memory as well as temporary files.
jmemsys.pas A skeleton with all the declaration you need to create a
working system-dependent JPEG memory manager.
Exactly one of the system-dependent modules should be configured into an
installed JPEG library (see install.doc for hints about which one to use).
On unusual systems you may find it worthwhile to make a special
system-dependent memory manager.
jmemdosa.pas BASM 80x86 assembly code support for jmemdos.pas; used only
in MS-DOS-specific configurations of the JPEG library.
Additional Applications
demo.pas Demo program, uses example.pas
example.pas Sample code for calling JPEG library.
test.pas Sample skeleton code for example.pas
cdjpeg.pas Declarations shared by cjpeg/djpeg modules.
cderror.pas Additional error and trace message codes for cjpeg/djpeg.
Not used, Those errors have been added to jdeferr.
cjpeg.pas Main program for cjpeg.
djpeg.pas Main program for djpeg.
jpegtran.pas Main program for jpegtran.- NOT READY YET
cdjpeg.pas Utility routines used by all three programs.
rdcolmap.pas Code to read a colormap file for djpeg's "-map" switch.
rdswitch.pas Code to process some of cjpeg's more complex switches.
Also used by jpegtran. - NOT READY YET
Image file writer modules for djpeg:
wrbmp.pas BMP file output.
wrtarga.pas Targa file output.
Image file reader modules for cjpeg:
rdbmp.pas BMP file input.
rdtarga.pas Targa file input. - NOT READY YET
This program does not depend on the JPEG library.
rdjpgcom.pas Stand-alone rdjpgcom application.
Archive Locations:
==================
[1] Thomas G. Lane, JPEG FAQ
in comp.graphics.misc and related newsgroups
[2] Wallace, Gregory K.: The JPEG Still Picture Compression Standard
ftp.uu.net, graphics/jpeg/wallace.ps.Z
[3] The Independent JPEG Group C library for JPEG encoding and decoding,
rev 6a.
ftp://ftp.uu.net/graphics/jpeg/
or SimTel in msdos/graphics/
[4] JPEG implementation, written by the PVRG group at Stanford,
ftp havefun.stanford.edu:/pub/jpeg/JPEGv1.2.tar.Z.
[5] PASJPEG.ZIP at NView ftp site
ftp://druckfix.physik.tu-chemnitz.de/pub/nv/
http://www.tu-chemnitz.de/~nomssi/pub/pasjpeg.zip
[6] Delphi 2.0 Image Viewer Application using PASJPEG, by Detlef Meister,
http://w3.rz.fthw-berlin.de/~meister/index.html
| 
Jacques Nomssi Nzali