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Amiga Collections: Topik
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Topik - Disk 06 - Graphix (19xx)(Topik Public Domain)(PD)[WB].zip
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Topik - Disk 06 - Graphix (19xx)(Topik Public Domain)(PD)[WB].adf
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GIF
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GIF2IP.doc
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1989-06-28
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Why would you want to convert GIF files to an obscure Amiga file format which
requires commercial software?
Because this was the quickest, dirtiest way to get rid of those ugly artifacts
you have to contend with when displaying 256 (or more) color GIF files in HAM
mode on the Amiga. Unfortunately, all of the IFF screen grabbers I've seen
save from the screen, so they naturally keep the artifacts. In addition,
images in GIF are stored with the full bits/pixel resolution as specified by
the accompanying palette. HAM mode pixels use inferred colors by operations on
previous pixels and are inherently less accurate than a true bitmap.
The best solution is to go to the file data and work with it from there. This
program loads the GIF file into memory and writes it out as a DigiView IP file
which consists of the three planes (RGB) written one right after the other with
a resolution of up to 7 bits per primary color. Since Digi-View is the only
program which allows you to perform operations on bitmaps with up to 21 bits/
pixel, it is the only obvious (and best) choice. To make the IP format easier
to work with, each pixel plane is padded with one bit to event things out to a
byte. So for a 320 by 200 image an IP file consists of 3 (RGB) 64000 byte
contiguous segments followed by a 12 byte file header for a total of 192012
bytes.
IP files can be loaded into DigiView by using the standard Load selection on
the menu. When loaded the panel will have to be set to defaults, so if the
picture starts to display a little wierd, then check the control panel. After
you get the pic looking like you want, you can save it IFF. I've had problems
loading IP files larger than the 320 by 200 size with v3.0 of DigiView. I have
no problems with v2.0. My belief is that IP was not fully implemented for
v3.0.
You can only load IP files as follows (by size):
320 by 200 (interlace off): 192012
320 by 400 (interlace on): 384012
640 by 400 (hi res/interlace on): 768012
Hope someone else finds this useful,
Wolfgang Kurtz, CIS 71410,724
(907) 258-4754 - Arctic Byte BBS
(907) 337-4136 - Northern Lights BBS
(907) 696-0886 - Eagles Eyrie BBS (9600 Baud HST)
P.S. Thanks to Lee Crocker for the basic code.
Coming soon:
Convert SIT, PIT, MAC files (Macintosh)
Convert EGA/VGA files (IBM)