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gifview.txt
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1985-11-19
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==============================================================================
== GIFcolor & GIFscale : Two Very Fast GIF Viewers For Colour Systems. ==
== Robert Barnhardt & Robert Steger, November 1990. ==
==============================================================================
== Files In This Archive ==
== """"""""""""""""""""""" ==
== GIFcolor.TTP - Viewer #1, uses the 16 most popular colors in the image. ==
== GIFscale.TTP - Viewer #2, maps the image to gray and tinted scales. ==
== GIFview.TXT - This text file. ==
==============================================================================
== GIFcolor and GIFscale are, of course, freeware. ==
== The programs in this archive are (C) 1990 Brain~Waves Freeware Group. ==
== GIF (Graphics Interchange Format) is (C) 1987 CompuServe, Incorporated. ==
==============================================================================
Why Another GIF Viewer? (2, even!)
"""""""""""""""""""""""""""""""""""
In the manner of most of the programs we write, these GIF viewers were
not conceived, planned, or developed in any sense of the word; rather, they
came into being virtually overnight, much like a pimple. It was quite a
surprise, then, when a use became apparent for them.
Most everyone keeps their GIFs on floppies, and these disks are often
quite full, correct? If we could develop these viewers into TTP programs
that could be "Installed Applications", they would be ideal in this
situation. Strangely, we actually did this, and so you hold in your hands
two of the smallest, fastest GIF viewers for the ST. (Ooooh.)
So, What Do I Do With Them?
""""""""""""""""""""""""""""
Method One
"""""""""""
From the desktop, double-click on either of the viewers, and a parameter
line should appear. Here's where you tell the viewer what GIF(s) you wish
to view by means of a path-and-file-specification string. I'll spell it out
for you with a few examples.
Multiple
""""""""
*.GIF Views all GIFs in the current directory
A:\*.GIF Views all GIFs in the root dir. of drive A.
A:\GIF\*.GIF Views all GIFs in the \GIF folder on drive A.
C:\A*.GIF Views all GIFs in the root dir. of drive C
that begin with the letter "A".
Single
""""""
YAWN.GIF Views "YAWN.GIF" in the current directory.
C:\SNOOZE.GIF Views "SNOOZE.GIF" in the root dir. of drive C.
D:\GIF\BORING.GIF Views "BORING.GIF" in the \GIF folder on drive D.
Um, at least I hope all of those would work...
Method Two
"""""""""""
Make either viewer (not both!) an "Installed Application" for file type
GIF. For those who don't know, here's a little explanation of how to perform
this.
Click once on one of the viewers from the desktop, thereby highlighting
it. Go up to the Options menu, and select "Install Application...". Set
the "Document Type" in the dialog box that appears to "GIF", click on the
OK button, and you're all set. You may now double click on a GIF picture
from the desktop, and the GIF utility that you have installed will load
and view that GIF with no further work on your part.
If you decide that you like the utility installed, arrange the desktop
in a manner that's visually appealing to you. This will probably be futile,
so when you decide that the desktop can't look good, select "Save Desktop"
from the Options menu. From now on, if you boot your computer with that
disk in the drive, the utility of your choice will be "Installed".
So, The Picture's Loaded...
""""""""""""""""""""""""""""
If you loaded a GIF picture from floppy, you will have seen a title screen
that briefs you on the various keys active (holding ALTERNATE will keep the
screen up, in case you're not a speed reader). This title screen will not
appear if a picture is loaded from any drive other than A or B (i.e. a
hard drive or ramdisk) for speed reasons, but if you'd like to see it in
this situation, simply hold down alternate while the GIF viewer is loading.
0 Selects true grey palette (GIFscale only).
1 to 6 Selects tinted palettes (GIFscale only).
ARROWS Scroll around picture, if larger than screen.
S Save palette and screen as a DEGAS PI1.
ENTER, SPACE, RETURN Next picture (exit, if viewing one picture).
UNDO, ESC Exit (abort multi-view, if applicable).
Not Like I Care, But How Do They Work?
"""""""""""""""""""""""""""""""""""""""
GIFscale allocates memory for the picture to be decompressed to, and then
allocates as big a file buffer as is possible. The GIF palette is converted
to a luminance value from 0 to 15 (black to white), and the entire picture is
decompressed and drawn according to these luminance values. Rarely looks
better than GIFcolor, but hey... variety is the spice, right?
GIFcolor is a bit more complex. After allocating buffers like GIFscale,
GIFcolor decompressed the entire picture (unconverted) to memory. While it
is being decompressed, a table of "popularity" values is being updated to
reflect how often each color in the GIF palette is being used. When this
stage is complete, GIFcolor then picks the 16 most popular colour from the
GIF palette and maps the rest of the colours in the palette to these colours.
Finally, the image is drawn with the calculated palette and lookup tables.
Neither of these programs has been optimized in the least. Actually,
we're afraid that if we return to them, we won't have a clue as to what we
did. Nevertheless, they will certainly be fixed up and upgraded in the
future. We've got to clean up the source for both, add comments, change
rudely named labels and so forth, but if you'd like the source, just get in
touch. Free, of course... the day we write something worth selling, we will.
For anyone who's interested, our next (minor) project is a GIF to LowRez/
Spectrum converter using RGB dithering (Burkes error dispersion). This will
look much better and work much faster than most anything else I've seen.
Finally, The Cold, Hard Facts...
"""""""""""""""""""""""""""""""""
Picture Resolution = BGIF ViewGIF FastGIF GIFscale GIFcolor
===============================================================================
BLIZZARD.GIF 320x200x32 = 1:07 37 10 6 6
DRAGEGG.GIF 320x200x256 = 1:00 31 9 5 5
+MICKEY.GIF 640x400x16 = ---- 1:37 ---- 11 11
*MONALISA.GIF 640x480x256 = ---- ---- ---- 20 20
===============================================================================
Program Size (+ RSC, if appl.) = 29600 82640 32215 3108 3070
===============================================================================
+ BGIF and FastGIF could not view MICKEY.GIF with 512K of memory.
* BGIF, ViewGIF, and FastGIF could not view MONALISA.GIF with 512K of memory.
This is not meant to demean any of the other programs in the table, but
merely to show that our programs do have a niche to fill. Time measurement
began at the moment the programs began to load the GIF (from floppy) and
ceased at the instant the picture was completely displayed.
That's It?
"""""""""""
Well, yeah... what did you expect? One warning: there is no support for
multiple images or local colour palettes in this issue of GIFcolor and
GIFscale. If someone can provide us with an image that doesn't work with
either of these viewers, the problem (unless it's with the picture) will
be corrected. If you have questions, comments, bug reports, or practically
anything worth relating, contact us in one of the following ways.
We'd like to hear some suggestions as to what sort of programs you'd like
to see written for the ST, so we won't write any useless trash. (Too late?
Ha ha, very funny...)
CompuServe: 73707,533
Phone : (416)/871-3868, the later, the better.
Address : Brain~Waves Freeware Group
619 Central Ave
Fort Erie, Ontario
CANADA L2A 3V6
In keeping with the holiday spirit, hello to Matt Rubelj, John Spirko,
Sandra ?, and company. Have a merry Christmas and a happy new year
everyone, and take care.
Robert Barnhardt
Robert Steger