seejpeg  v1.6.1		$Id: README,v 1.6 1996/11/01 19:15:36 evan Exp $

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Copyright (C) 1993-1996 Evan Harris

Permission is granted to freely redistribute and modify this code,
providing the author(s) get credit for having written it.
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seejpeg is another JPEG viewer which utilizes svgalib and contains
limited GIF, PPM, BMP and TARGA viewing support.

The most useful feature of seejpeg is that it automatically decides on
the "best" video mode to use based on the image being displayed and
the video card being used.  To aid it, various hints may be given as
program options.  In the worst case, it may be overridden.

Video modes supported are limited to 1280x1024, 1024x768, 800x600,
640x480 and 320x200 in 256, 32K or 16M colours (assuming the video
card, and svgalib, supports these modes).  Logical screen sizes are
only limited by the size of video memory.

If the image is larger than the screen size the arrow keys may be used
to scroll around that part of the image which could be loaded into
video memory.  The Backspace key can be used to move to the previous
image.  Pressing any other key moves to the next image, or exits the
program.

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Program options
===============

-c	CENTRE IMAGE

	If the image is smaller than the video mode, the image is
	centred on the screen.

-q	QUANTIZE PICTURE (256 colour mode)		(JPEG only)

	This option forces the image to be quantized into a colour map
	with 256 entries, and subsequently seejpeg uses a 256 colour
	mode.  If this option is not given seejpeg will not use a 256
	colour mode unless the TESTMODE is not available (see below)
	in which case it will implicitly set -q.  The default
	quantization to use is two pass quantization - this is memory
	intensive and may cause the machine to page if the image is
	large or memory is small.  This should be the only occasion in
	which seejpeg causes a machine to page.

-1	ONE PASS QUANTIZATION (-q implicit)		(JPEG only)

	As -q, except that it uses one pass quantization.  This does
	not cause a machine to page, but the results are worse, unless
	the image is greyscale.

-g	FORCE GREYSCALE MODE (-1 implicit)		(JPEG only)

	Display the image in greyscale.  This is not necessary for an
	image compressed using the greyscale option on cjpeg as this
	mode will be set automatically.  It can be used for images
	compressed without the greyscale flag, or for displaying
	colour images in greyscale.

-v	VERBOSE

	Display the video modes being used, the program version number
	and lots of other stuff.  Without this option, seejpeg
	operates silently.

-w	ONLY USE WIDTH TO DETERMINE VIDEO MODE

	By default, the video mode chosen is the smallest one possible
	which is not smaller than the image.  This may not be
	desirable for long, thin images.  It may be preferable to
	choose the video mode based on the width only, rather than the
	width and height, in which case this option should be used.

-f F	SET FUZZ FACTOR TO DETERMINE VIDEO MODE

	A video mode is selected if it is larger than the image.
	Using this option allows a video mode to be selected if it is
	larger than (or equal to) F * image_width and F *
	image_height.  Currently, F must be in the range [0.5,1.0].
	This option may be used in conjunction with -w to only use the
	image width.

-F S	FORCE THE USE OF THE GIVEN VIDEO MODE

	To completely override the video mode selection routines a
	video mode string (e.g. G640x480x32K) may be given instead.
	If this is a 256 colour mode, quantization (-q) is
	automatically selected.

-dx	DOUBLE THE SIZE OF THE IMAGE IN THE X DIRECTION

-s T	SHOW THE IMAGES IN A SLIDESHOW

	Each image is shown for T seconds.  The images can be scrolled
	when being showed in a slideshow.  The slideshow cannot be
	stopped or paused, except by the interrupt character
	(e.g. ^C).

-C	CYCLE THROUGH ALL IMAGES

	The program does not exit after showing all the images,
	instead it returns to the first image and shows them all
	again.  Normally this can be stopped by pressing the Q key, at
	which point it will continue to show all images in the cycle
	and then stop.  When showing the images in a slideshow this
	option will cause the slideshow to run forever (until
	interrupted by, e.g., ^C).

-r	RANDOMISE THE ORDER OF THE IMAGES

	The images are shown in a random order.  If -C is specified, a
	new random order is selected on each cycle.


In addition to colour and greyscale JPEG formats, GIF, PPM, BMP and
TARGA image formats are supported to a limited degree.  If the image
is in GIF, PPM, BMP or TARGA format the -q, -1 and -g options are
inoperative and, as a result, some video modes are not available for
selection using -F.

Unfortunately, due to a limitation in libjpeg, the GIF support has to
perform its own colour map construction so it can use 256 colour
modes.  This may cause problems, although I haven't seen any yet.  GIF
support currently only uses 256 colour modes, however changing this
should be easy, if the demand is there for it.  GIF support has had
limited testing.

PPM support is barely tested.  It uses 16M or 32K modes for colour
images, and 256 modes for greyscale images.

BMP and TARGA support is completely untested.  The -targa option of
cjpeg is not included in seejpeg, let me know if something like it is
required.

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Compiling
=========

NOTE: The file jpeglib/libjpeg.a was compiled on an a.out system, not
an ELF system.  If you have an ELF system you should either get the
JPEG v6 distribution and make libjpeg.a up yourself, or try to compile
the shared library version (see below).

This program was tested using version 1.2.7 of svgalib.  It should
also work with later versions.

The following symbols can be defined in the Makefile:

NO_32K_CASCADE	If the best mode is available in 16M and 32K modes and
		the complete image doesn't fit in memory using the 16M
		mode, the 16M mode is discarded and 32K mode used instead.
		If you define this option this action does not happen.
		The only time I can think of this option being useful is
		if a video card supports 16M modes but not 32K modes.

TESTMODE	This video mode is tested for -
		If the video card supports it, we assume that hicolor or
		truecolor (32K or 16M) modes are available.
		If the video card doesn't support it, we assume that only
		256 colour modes are supported.
		If this is not set in the Makefile, it is assumed to
		be G640x480x32K.  If there is a video card which supports
		hicolor or truecolor but not this mode, let me know of
		a better default to test for and I'll change it in the
		next release.

BUG_WORKAROUND  Some versions of svgalib with some video cards can
		scramble the video mode when multiple files or
		slideshows are shown.  This appears to be avoided
		somewhat if the text video mode is set between each
		picture.  This is what the workaround does.  This may
		not be needed for some versions of svgalib or some
		video cards.  It is for my CLGD5426 based card with
		svgalib 1.06.  This option is defined by default in
		the makefile.

Unless you change one of these options, or the default binary
location, changing the Makefile should no longer be necessary.

PIX_ALIGN is no longer set in the Makefile.  If you wish to try
different a value for it, see chiptype_init() in display.c.  If you
lower PIX_ALIGN and it works, send me the changes.

You can build a version of seejpeg which uses the libjpeg-6 shared
libraries (or even a version of libgr with the v6 JPEG libraries).
This shared library is NOT included with seejpeg.  It is available on
sunsite in /pub/Linux/libs, amongst others.  I have tested it, and it
does work.  Note that you may need to adjust the GRHEADERS definition
in the Makefile to find the JPEG header files.  The headers in jpeglib
should not be used, in case they are different.

The current release has not been tested (by me) on an a.out system,
although the library in jpeglib is an a.out one.

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Acknowledgements
================

The following people have contributed to the development of seejpeg.
Thanks everyone.

Harm Hanemaayer <hhanemaa@cs.ruu.nl>
	ongoing svgalib development, putting up with lots of silly
	questions, providing lots of useful information, and a makefile
	bug report
<wolter@wppc9.oz.au>
Jean-Francois Cordeau <cordeauj@jsp.umontreal.ca>
Peter Mutsaers <muts@compi.hobby.nl>
<ahughes@muddcs.cs.hmc.edu>
	makefile bug report in 1.0
Jeff Grills <jefftep@cs.utexas.edu>
	colour lookup (256 colour mode) bug report in 1.2
Michael Weller <eowmob@exp-math.uni-essen.de>
	PIX_ALIGN patches against 1.1, prompting to add multiple
	images and the slideshow
Nils Rennebarth <nils@exp-math.uni-essen.de>
	described how to compile with libgr-1.3 cleanly
Lord Maximilien <lordmax@ix.netcom.com>
	helped fixed Trident 800x600 problems, suggested the new options 
	which were added in 1.6 

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Feedback
========

The current version was compiled and tested with svgalib version 1.2.7
and a 1MB CLGD5426 based video card.  There are no known bugs with
this configuration (in seejpeg, that is 8-).  If you find a bug with
any configuration please report it, including all the information
displayed using the "-v" option.

As of version 1.2, I have considered seejpeg "finished".  Future
releases will primarily be bug and compatibility fixes, although new
features may be added as well (as they were in 1.4, 1.5 and 1.6).

Please send any feedback, especially bug reports, to:

Evan Harris (evan@cs.mu.oz.au)
