readme

speech signal process tools

@(#)README	1.2  11/8/90

XLOADIMAGE - X11 Image Loading Utility

WHAT IS IT?

This utility will view several types of images under X11, or load
images onto the root window.  The current version supports:

	Faces Project
	GIF
	Portable Bitmap (PBM)
	Sun Rasterfile
	X11 Bitmap
	X Pixmap

A variety of options are available to modify images prior to viewing.
These options include clipping, dithering, depth reduction, zoom
(either X or Y axis independently or both at once), brightening or
darkening, and image merging.  When applicable, these options are done
automatically (eg a color image to be displayed on a monochrome screen
will be dithered automatically).

COMPILING

There are three ways to compile xloadimage, depending on what
environment you have.

If you are compiling under the X11R4 distribution, the apropriate
Imakefile is included and you should compile as with any other client.
I haven't personally tested this, but if it's broken it'll be easy to
fix.

If you have gcc on your system, and it's not gcc 1.37, compile via
"make -f Makefile.gcc".  Gcc should be used if it works because the
strength-reduction and inline-functions directives dramatically
improve performance of some operations.  Please note that use of gcc
on some systems, particularly Sun-4, may cause problems, and that gcc
1.37 will not work due to an optimizer bug which causes GIF image
loading and colormap reduction to fail.  If improper behavior is
noticed after compiling with gcc, please try using Makefile.std before
reporting a problem.

Normal compilations can be done via "make -f Makefile.std".  This
invokes the standard cc using the -O flag.

WORKAROUNDS FOR BROKEN SERVERS

Some servers which use odd-depth displays (eg not 1 or a multiple of 8
bits) do not correctly handle a plane mask with GXcopy.  If your
server displays color images in only two colors although it supports
more colors, add a -DSERVER_HAS_BROKEN_PLANEMASK to CFLAGS in the
Makefile.  Some Visual X-19 Turbo displays have this problem; you
should request an updated ROM if you have one of these.

INSTALLATION

After compiling and installing xloadimage, I recommend linking or
symlinking to the executable with the names "xview" and "xsetbg".  The
default behavior is slightly different when invoked with these
commands (they're also easier to type).  If you have a public image
area you should consider setting the SYSPATHFILE option in the
makefile and setting up a system-wide configuration file.  See the man
page for information on the format of this file.

IMPLEMENTATION

Most functions are not particularly fast, and some functions use
simple-minded algorithms deliberately over more advanced ones.  I
stressed portability over all and simplicity over performance.  I
believe the result is a usable, portable tool which should serve the
needs of most users.

The source code is basically in two parts: image manipulation routines
and everything else.  The image manipulation routines should be
completely independent of X, thus allowing people to use them under
other graphical systems.  No guarantees here, but I tried.

Performance-oriented people will notice that when loading a color
image, the colormap of the image is minimized (and all pixel values in
the image changed), then the colormap is redone (and all pixel values
in the image changed again) before sending to X.  This could be
reduced to only one remapping of the image but I wanted to keep the
image from X's grubby (greedy?) hands as long as possible, and the
image merging function really wants the image to have a minimized
colormap.

OWNERSHIP

I used a modified version of the MIT X Consortium copyright with all
of these functions, thereby allowing full freedom with the code so
long as the copyright notices remain intact.  Free code can be good
code.  All contributions have similar notices.

SUGGESTIONS AND BUG REPORTS

Suggestions and bug reports should go to:

	Jim Frost
	[e-mail]
	..harvard!saber!jimf

Please include the version number and sample image data if you are
reporting a bug.

Functions implementing new image types are welcomed; mail them to the
same address and I'll do my best to distribute them.  Try do send them
as public domain so I can keep the number of differing copyright
messages to a minimum -- I'll use my standard message and leave the
implementor's name and information in the file for credit.  I wouldn't
copyright this stuff at all except that it's a requirement for X11
distribution.

THANKS

Special thanks to the crew at the Boston University Graphics Lab for
their assistance and sample images, and to [e-mail] for his simple
dithering algorithm (or what's left of it).  Real special thanks to
Kirk L. Johnson ([e-mail]) for a very nice GIF loader and
dithering routine, to Mark Snitily (zok![e-mail]) for 386/ix
compatibility work, to Andreas Stolcke ([e-mail])
for miscellaneous bug fixes, to Anthony A. Datri ([e-mail])
for adding the class hint, to Mark Moraes ([e-mail]) for
the slideshow colormap fix, to Gregg Townsend ([e-mail]) for
a suggested dithering routine, to Brian Frost ([e-mail])
for changes for VMS, to Chip Horstman for G3 FAX support, and to Deron
Dann Johnson ([e-mail]) for fixing the RetainTemporary bug.

HISTORY

Patch 01 contained a new Makefile.std, Makefile.gcc, and Imakefile.
It contained a bug-fix to sendImageToX() which allowed bitmaps to be
sent from little-endian machines (eg VAX, 80386) correctly, and a fix
to xbitmapLoad() to allow correct loading of X10 bitmap images.  An
enhancement to imageInWindow() which allowed exiting from image
windows by typing 'q' was submitted by Chris Tengi
([e-mail]) and was included.  The previously missing
file 'patchlevel' was included.

Patch 02 contained modifications to the Makefiles, support for the X
Pixmap image type, a different dithering algorithm that didn't blow
the image up (with the old one moved to halftone.c), and a bug fix to
zoom.c to correct problems when zooming bitmaps.

Patch 03 contained a new loader for GIF files.  The dither bits array
in dither.c was changed so it worked properly, and both dither.c and
halftone.c had minor bugs fixed.  Merge.c was modified to correct bugs
when merging RGB images.  Pbm.c was modified to handle raw format
images.  Root.c was modified to deny image loads which would change
the root window's colormap.  Send.c was modified to use shared colors
whenever possible and to handle color displays which have depths which
are not a multiple of 8.  Window.c was modified to avoid deleting the
default colormap, allowing proper operation on some servers prior to
X11R3 patchlevel 08.  There were many miscellaneous bug fixes.

Patchlevel 04 contained an enhancement to root.c to use
RetainTemporary and KillClient(disp, AllTemporary) so that it could
clean up after itself when reloading.  The -quiet and -zoom options no
longer cause garbage to be displayed for the image title.  A small bug
in new.c that caused incorrect allocation of bitmap images was fixed.
Several calls to XCreateColormap were missing the "visual" parameter
in send.c; this was fixed.  A bug relating to -border and monochrome
displays was fixed.  There were several changes to the Imakefile and
Makefiles.

Patchlevel 05 contained enhancements to allow slideshows and
fullscreen viewing, some bug fixes related to scrolling around within
images, Saber-C makefile enhancements, a bug fix to the halftoning
title, and the addition of greyscale Sun Rasterfile support.

Patchlevel 06 contained support for G3 FAX images, bug fixes to
merge.c to fix some signed/unsigned errors and clipping problems,
changes to root.c to make previously allocated resources be freed
properly, and a completely new dithering routine.

This derivative of version 1.06 of xloadimage has an additional
option to allow slideshows under program control; also included is
a program "next_slide" for controlling the advance from one image
to the next.  Although written by Entropic Research Laboratory, the
next_slide program and Entropic's additions to xloadimage are
free software; they are NOT covered by ERL's license agreements for
ESPS and waves+; and the fees paid to ERL as part of those license
agreements do NOT include any payments for this software.  The
next_slide program and Entropic's additions to xloadimage are
covered by the same type of "MIT-style" copyright notice and disclaimer
of liability that cover the main body of xloadimage and other
contributions thereto.  Briefly, you are free to use this software,
copy it, and pass it on to other people provided that the relevant
notices remain intact.  See the source files for the full text of
the notices.