nv89-nun@alv.nada.kth.se (Nicklas Ungman) (03/01/91)
I've got a copy of Intro to Amiga IFF ILBM Files and Amiga Viewmodes and it says that "if the picture is 6 planes deep and has no CAMG chunk, it is probably HAM". Is this really correct? If it is, it means I have to put a 'CAMG' chunk if I want to save a non-ham 6-bit picture. Does it apply to 7 and 8-bit pictures too? The Intro also says that "Hopfully,... the package that saved it properly saved a CAMG chunk". How is "probably" and "hopefully" defined in an IFF algorithm? Does they implement a random function to determine if a CAMG chunk will be included :?) I also would like to know if Amiga programs (like DeluxePaint) can handle 6, 7, 8 and 24-bit IFF pictures. If someone has any answers please post them. /Nixxon
Marco.Eichelberg@arbi.informatik.uni-oldenburg.de (Marco Eichelberg) (03/01/91)
nv89-nun@alv.nada.kth.se (Nicklas Ungman) writes: >I've got a copy of Intro to Amiga IFF ILBM Files and Amiga Viewmodes >and it says that "if the picture is 6 planes deep and has no CAMG chunk, >it is probably HAM". Is this really correct? If it is, it means I have >to put a 'CAMG' chunk if I want to save a non-ham 6-bit picture. Does it >apply to 7 and 8-bit pictures too? >The Intro also says that "Hopfully,... the package that saved it properly >saved a CAMG chunk". How is "probably" and "hopefully" defined in an IFF >algorithm? Does they implement a random function to determine if a CAMG >chunk will be included :?) >I also would like to know if Amiga programs (like DeluxePaint) can handle >6, 7, 8 and 24-bit IFF pictures. 1. As you might know, the Amiga is not able to display more than 32 colors at a time in FULL MULTICOLOR. That means, if you want to display a 6 bitplane picture, you can do this as HAM (hold and modify) or as EXTRA-HALFBRITE. Halfbrite means that the 2nd half of the palette is identical to the 1st half, but with less (half) brightness. The HAM-Mode can display all 4096 colors simultaneously, but from one pixel to the next you can only choose one of 16 colors or change one of the three color-values red, green and blue. The problem is that IFF has no mean to save information about the way the picture has to be displayed. For IFF every picture is multi-color. So a program has to determine on its own, if a 6-bitplane picture is HAM or Halfbrite - or even a true 64 color picture from another computer. This is *usually* done by assuming that a 6-bitplane-picture with CAMG chunk is Halfbrite and everything else with 6 bitplanes is HAM. The problem is: this way of determining the display mode is *not* part of the IFF standard, but a kind of work-around. This means, that there is (for a program) no way to be shure that the assumption about the mode is true. 2. One idea of IFF is to make Load and Save shure. So an IFF loader has to provide means to load a picture even if a chunk that is not of great importance is missing. An IFF save routine *should* write all needed information, of course. 3. As far as I know, there is no Amiga program that can handle more than 6 bitplanes. There are, of course, programs for HAM and halfbrite. Some video-digitizers use 24-bitplane-pictures and thus have software to handle 24-bit IFF pictures. The problem is: There is no standard for 24-bitplane-pics. This means that two programs writing 24-plane-pics *may* save the bitplanes in opposite order. Best Regards, Marco Eichelberg
dewolfe@ug.cs.dal.ca (Anarchy for Peace) (03/02/91)
In article <4923@uniol.UUCP> Marco.Eichelberg@arbi.informatik.uni-oldenburg.de (Marco Eichelberg) writes: >nv89-nun@alv.nada.kth.se (Nicklas Ungman) writes: > [stuff nuked] >3. As far as I know, there is no Amiga program that can handle more >than 6 bitplanes. There are, of course, programs for HAM and halfbrite. >Some video-digitizers use 24-bitplane-pictures and thus have software >to handle 24-bit IFF pictures. The problem is: There is no standard >for 24-bitplane-pics. This means that two programs writing 24-plane-pics >*may* save the bitplanes in opposite order. > Not any more guy, there is a 24 bit IFF standard put forth from Commodore last year. It's form name is called RGB8 (much like gif in that it stores 8 bit colour map for 24 bits). Also, there is a true 24 bit standard, but I forget what it is called... This is what The Art Department, Imagine and the Video Toaster save their stuff in. >Best Regards, > >Marco Eichelberg -- Colin DeWolfe dewolfe@ug.cs.dal.ca
kdarling@hobbes.ncsu.edu (Kevin Darling) (03/02/91)
nv89-nun@alv.nada.kth.se (Nicklas Ungman) writes: >I've got a copy of Intro to Amiga IFF ILBM Files and Amiga Viewmodes >and it says that "if the picture is 6 planes deep and has no CAMG chunk, >it is probably HAM". Is this really correct? I believe what happened is that the "half-brite" 6-plane mode came along later... early Amigas didn't have it. So ILBM usage was originally very machine-dependent in that respect: it was automatically assumed that 6 planes meant HAM mode on Amigas. CAMG was a way of correcting this problem, but obviously some people missed getting "the word" in time. regards - kevin <kdarling@catt.ncsu.edu>
al158305@mtecv2.mty.itesm.mx (Gustavo Cordova Avila) (03/06/91)
Marco.Eichelberg@arbi.informatik.uni-oldenburg.de (Marco Eichelberg) writes: >to handle 24-bit IFF pictures. The problem is: There is no standard ^^^^^^^^^^^^^^^^^^^^ >for 24-bitplane-pics. This means that two programs writing 24-plane-pics ^^^^^^^^^^^^^^^^^^^^ >*may* save the bitplanes in opposite order. >Best Regards, >Marco Eichelberg Oops, sorry to tell you, but there is a 24 bit standard called iff24 (or something like that). Gustavo Cordova -- /====================================================================\ | Gustavo Cordova Avila | Electronics Systems Engineering | | pl158305@tecmtyvm.bitnet | major, @ Monterrey Tech, Mexico. | | al158305@mtecv2.mty.itesm.mx | I.T.E.S.M. Monterrey, NL, Mexico |
jbickers@templar.actrix.gen.nz (John Bickers) (03/07/91)
Quoted from <NV89-NUN.91Mar1104205@alv.nada.kth.se> by nv89-nun@alv.nada.kth.se (Nicklas Ungman): > I've got a copy of Intro to Amiga IFF ILBM Files and Amiga Viewmodes > and it says that "if the picture is 6 planes deep and has no CAMG chunk, > it is probably HAM". Is this really correct? If it is, it means I have This is an assumption that a person writing a display program is supposed to be able to make. People who write programs that save ILBMs should be aware of it too. It's just a guideline, which is why words like "hopefully" appear... :) > to put a 'CAMG' chunk if I want to save a non-ham 6-bit picture. Does it > apply to 7 and 8-bit pictures too? Saving a CAMG chunk is no big deal. Bad idea if the data does not actually fit any Amiga display mode, though. > I also would like to know if Amiga programs (like DeluxePaint) can handle > 6, 7, 8 and 24-bit IFF pictures. Version II of DeluxePaint can't. Unless a program is supposed to know about undisplayable pictures, the chances are good that the excess bitplanes will just be ignored. There's also a chance some programs will crash, but that's poor programming on the part of their authors - I wouldn't worry about it. > If someone has any answers please post them. Ok. Something wrong with email? > /Nixxon -- *** John Bickers, TAP, NZAmigaUG. jbickers@templar.actrix.gen.nz *** *** "Patterns multiplying, re-direct our view" - Devo. ***
slandrum@ntg.uucp (Stephen Landrum) (03/08/91)
>Quoted from <NV89-NUN.91Mar1104205@alv.nada.kth.se> by nv89-nun@alv.nada.kth.se (Nicklas Ungman): >> I also would like to know if Amiga programs (like DeluxePaint) can handle >> 6, 7, 8 and 24-bit IFF pictures. > > Version II of DeluxePaint can't. Unless a program is supposed to > know about undisplayable pictures, the chances are good that the > excess bitplanes will just be ignored. There's also a chance some > programs will crash, but that's poor programming on the part of > their authors - I wouldn't worry about it. DPaint III can handle the 6-bit Extra-Halfbrite mode (where every color past 31 is half the value of the one 32 previous). HAM mode and a true 64 color palette cannot be used by DPaint III. Some other paint programs for the Amiga work in HAM mode and can (I think) handle images that come in as 24-bit IFF and possibly 8-bit (I'm less certain) as well. -- Stephen H. Landrum VOICE: (415) 813-8909 UUCP: ...apple!ntg!slandrum USNAIL: New Technologies Group Inc. 2468 Embarcardero Way, Palo Alto CA 94303