richard@gryphon.CTS.COM (Richard Sexton) (07/14/87)
I just notived in todays Computer Graphics Today that compuserve Inc has
defined an interchangable graphics format (GIF) to allow Mac's and IBM's
and other computers to exchange pictures. They go on to note that GIF
readers are also available for the Amiga and ST's.
Is there some reason they did'nt use IFF ?
Do IFF readers exists for *other* machines (Suns, Apollos ?)
--
Richard Sexton
INTERNET: richard@gryphon.CTS.COM
UUCP: {akgua, hplabs!hp-sdd, sdcsvax, ihnp4, nosc}!crash!gryphon!richardbarry@aurora.UUCP (Kenn Barry) (07/16/87)
In article <954@gryphon.CTS.COM>, richard@gryphon.CTS.COM (Richard Sexton) writes: >I just notived in todays Computer Graphics Today that compuserve Inc has >defined an interchangable graphics format (GIF) to allow Mac's and IBM's >and other computers to exchange pictures. They go on to note that GIF >readers are also available for the Amiga and ST's. >Is there some reason they did'nt use IFF ? Why, because Amiga is an oddball machine whose existence isn't even acknowledged by the Big Guys, of course ;-). But, seriously, folks... I've downloaded the GIF software and some pics from Compuserve, and it does have one great advantage over IFF: the same picture is a much smaller file when GIF encoded than IFF encoded - anywhere from 1/2 to 1/8 the IFF size. When you're downloading at 1200bps at Compuserve's exorbitant hourly rates, that's a big plus. I noticed in the docfile for it that it supports huge resolutions, too - over 16K X 16K, I presume for the purpose of encoding pics intended for a laser printer. Does IFF support this? I know, don't answer, I should read the manual. One real stupidity of GIF, though. The maximum # of colors supported is 256 (somebody's wearing IBM-trademarked blinders). The conversion software for converting Amiga's IFF pics to GIF doesn't understand HAM at all; it doesn't cut the # of colors down, it just ignores the HAM flag and screws up the colors completely. If you've ever tried viewing a HAM pic with one of the old 'show' utilities that didn't understand HAM mode, you've seen what the resulting picture looks like. As for going the other direction: I haven't found any pics on Compuserve, so far, that use more than 16 colors, so I don't know what the Amiga's GIF software would do with a 256 color pic. What it should do, ideally, is convert it to HAM mode, of course; what it probably actually does is reduce the # of colors. - From the Crow's Nest - Kenn Barry NASA-Ames Research Center Moffett Field, CA ------------------------------------------------------------------------------- ELECTRIC AVENUE: {hplabs,seismo,dual,ihnp4}!ames!aurora!barry
bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt) (07/17/87)
In article <794@> barry@aurora.UUCP (Kenn Barry) writes: >In article <954@>, richard@gryphon.CTS.COM (Richard Sexton) writes: >> >>I just notived in todays Computer Graphics Today that compuserve Inc has >>defined an interchangable graphics format (GIF) to allow [computers like >>the Mac, IBM, Amiga, ST etc.] to exchange pictures. >>Is there some reason they did'nt use IFF ? > I noticed in the docfile for it that it supports huge >resolutions, too - over 16K X 16K, I presume for the purpose of encoding >pics intended for a laser printer. Does IFF support this? I know, don't >answer, I should read the manual. Absolutly. IFF files have *LOTS* of elbow-room. A 65535*65535 picture would fit real comfortably in a IFF "ILBM" form, though most IFF readers would probably either choke on this, or clip it down to reasonable size. Compuserve *COULD* have used an IFF file for GIF without giving up anything. If the compression of "ILBM" was not enough, they could have even designed a new one. (Existing readers would need to be upgraded, but that's a lot less work than conforming to a totally NEW standard) IFF is a quite an asset for the Amiga to have had from the start. As its planners intended, IFF is also starting to creep to other computers like the Apple Macintosh. To clear up a point: "IFF" is much more than a graphics interchange format. It is a standard for creating all sorts of interchangeable files (The acronym stands for "Interchangeable File Format"). It was defined by Commodore-Amiga and Electronics Arts. One of the standard types of IFF files that has been defined can contain a picture (The "ILBM" mentioned above). Other IFF definitions exist for sampled sound ("SVX8"), simple musical score ("SMUS"), etc... Developers are encouraged to save their application's data in IFF files, and then publish the format. Applications from different manufactures can then easily swap information back and forth. "SPRD" could be a standard for spreadsheets, etc... "Secret" IFF types are also possible. Existing IFF "forms" can be expanded at any time, often without affecting forward OR backward compatibility. ----------------------------- |\ /| . Ack! (NAK, EOT, SOH) {o O} . ( " ) bryce@cogsci.berkeley.EDU -or- ucbvax!cogsci!bryce U "Success leads to stagnation; stagnation leads to failure."
johnmac@fawlty.towers.oz (John MacLean) (09/12/90)
Thanks to those who replied.
I now have my software reading/writing/displaying/transporting/cutting/pasting
all IFF ILBMs including HAMs.
I have not tried SHAMs as I do not have any samples.
I have one more question:
The carried over RGB to the first pixel on a scanline for a HAM; is it:
- the background color (color index 0)
- black (RGB $000) or some other constant.
- the last value of the previous line (in which case what is the carried over
RGB value for the first pixel on the screen)
- something else.
Please respond by E-mail. Although we get Amiga newsgroups, they are usually
deleted before I get a chance to read them (you have to be quick).
Thanks, John MacLean.
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