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HamGIF.notes
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1978-05-20
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HAMGIF (aka GIFFY version 2.5)
WARNING - This is a PRE-release version. It is possible that it contains
bugs. The features included in this program will be included in GIFFY
version 3.0, which ought to be ready sometime in the Spring of 88. This
program is being released at this time due to a number of people who
requested that I support HAM displays. This program does that, although
somewhat slowly.
-------------------------------------------------------------------------
This program is a somewhat modified version of GIFFY2 which displays
certain pictures in HAM mode on the Amiga. It will automatically switch
to HAM mode for any picture with more than 32 colors.
As with GIFFY2, you can specify a list of files to display, including
using wildcards to specify more than one file. It will automatically
examine each file to see if it is a GIF file. It will automatically switch
resolutions to match the picture, and will enter HAM mode if the picture has
over 32 colors.
It will also automatically scale any picture in HAM mode which is
wider than 320 dots by 1/2 horizontally. This allows 640 x 400
or 640 x 200 pictures (very common resolutions...) to be shown on
the Amiga screen in what should be close to the proper aspect ratio.
It does not, in this case, remove pixels... Rather it *averages* pairs
of pixels together. So the total number of actually displayed colors
could be significantly larger than the amount specified in the file.
I have found that this works fairly well.
Note that for determining number of colors, I am depending on the number
of colors actually in the color map. So if the color map says there are
256 colors but only uses 16 of them (like FRBD.GIF does...), I am going into
HAM mode anyway...
Usage notes - This program ought to display pictures with 32 or less
colors identically to GIFFY 2.0. The -d, -r, -c, and -s flags ought to work
as usual, although the -a flag is effectively ignored in this release.
(See command line parameters, below...)
Displaying HAM files is S L O W... Part of it is due to the decoder, but
most of it is due to the conversion to HAM.
Command line parameters:
There are five optional flags:
-d<len> - This flag changes the length of the delay between each
GIF file displayed. Note that this delay is the time from
the completion of display of one GIF file to the *start* of
display of the next GIF file. Display time is extra.
The value <len> is a decimal number in seconds. For
example: -d5 would delay 5 seconds between files.
The default is a 10 second delay.
-c Normally when the next GIF file is displayed, the screen
is cleared. Most people probably will like it this way,
but in some cases (most notably when your disk contains many
NON interlaced pictures ["interlaced" here being the GIF
file format, not necessarily the 400 line graphics mode...]
all of the same resolution...) you might find it more
esthetically pleasing to simply display right over the
previous picture without clearing the screen. This flag
turns off the clearing.
(Note that when the screen resolution changes, or the mode
is switched into or out of HAM, the screen is necessarily
cleared in all cases.)
(HAM pictures probably don't look very good with this
flag turned on...)
-r This flag tells the program to repeat the entire list of
files continuously until the user stops the program by
clicking on the close box. Normally, the program will show
the entire list of files, and holds on the last file until
the close box is clicked.
-s One annoying feature of the slide show is that when you
switch resolutions, the Workbench pops up for an instant.
If this annoys you, you can blank it out with this flag.
Not perfect, but better. (It eats up some memory,
though...)
-e This flag only has meaning for HAM pictures. When
specified, it turns on a smoothing algorithm, which tends
to blur edges a bit, but also can result in a better looking
picture, especially when the original was dithered before
encoding as a GIF image. (This type of dithering tends to
result in badly colored horizontal line segments in sections
of the picture. If you see this type of thing, try using
this flag to clear it up...)
There may be one or more filenames, any or all of which may be standard
Amiga search patterns. For example: "HAMGIF A#? B#?" would show all GIF
files in the current directory which begin with "A", followed by all of
the GIF files in the current directory which begin with "B".
During display, if you click on the close box at any time, you will
exit the program. If you click anywhere else, you will skip the current
image and begin displaying the next one. (Useful for previewing a whole
bunch of images...)
To get a quick summary of this information, run HAMGIF with no flags and
no filenames.
-------------------------------------------------------
Things on the wish list for GIFFY 3.0
(Who knows when? Not real soon, unfortunately... Spring, most likely...)
- Faster decoding/rendering, especially in HAM mode...
- Ability to scroll screen around for pics too large
- Smoother resolution switching
- Wipes/Fades/Dissolves in Slide Show
- Save image as IFF.
- Clean up multiple images in HAM mode... (This is gonna look *weird*
for a while folks... You can try it, but it will come out strange...)
It seems likely that GIFFY will break into two programs: One for slide
shows, and one for working with a single image. (The latter to get the nice
things like scrolling and save as IFF...)
HAMGIF is freely redistributable. This means you can give it to anyone you
like. It is NOT, however, intended for commercial sale.
When you give this program away, be sure to also give this file. It
contains information some user somewhere will eventually want to see.
Comments and suggestions are always welcome...
-->Steve Bennett Compuserve:[70046,441] 01/03/88