johnm@trsvax.UUCP (09/03/88)
You've misunderstood GIF. GIF is COMPLETELY display independent. The decoder simply gets a file that has between 2 and 256 colors in it and information about its size and then IT will decide how best to display it. It is true that a lot of GIF pictures nowadays have the full 256 color palette filled and thus they look MUCH better on a VGA but any good EGA decoder will still display the file and just attempt to dither (or something) to make the picture look better when it displays it. I know FASTGIF does some dithering when pictures with a large number of colors on the EGA and I'm sure there are others too. Hope that helped, John Munsch
mdf@tut.cis.ohio-state.edu (Mark D. Freeman) (09/06/88)
In <2777@jpl-devvax.JPL.NASA.GOV> carlos@beowulf.JPL.NASA.GOV (Carlos Carrion) writes: > Is there a product out that converts vga graphics to ega? >e.g., if I take a vga .GIF picture, how can I get an ega .GIF reader >to display the pix? I understand that the resolutions and # of bit planes >are different. can it be done? Yes, this is the beauty of .GIF format. The viewer will display what it can of the image. Some will scale the image to the new screen size, others will enable you to scroll the screen around an image too large for it (in pixels), and they all try to do something reasonable about the colors. Of course, an image recorded with 256 colors may not look great on a 16 color display. There are many .GIF viewers in the PICS FORUM on CompuServe, all of which are public-domain or ShareWare that have a variety of features. Someone recently put a utility up there that will do some analysis of a VGA .GIF file and apply some intelligence to the elimination of pixels and colors so that the resulting file will look as good as possible on an EGA. However, the interpolation done on the fly by the regular .GIF viewers are usually good enough. Disclaimer: I speak only for myself, not my employer. -- Mark D. Freeman (614) 262-1418 Applications Programmer, CompuServe mdf@tut.cis.ohio-state.edu [70003,4277] ...!att!tut.cis.ohio-state.edu!mdf Columbus, OH Guest account at The Ohio State University
mdf@tut.cis.ohio-state.edu (Mark D. Freeman) (09/13/88)
In <2811@jpl-devvax.JPL.NASA.GOV> carlos@beowulf.JPL.NASA.GOV (Carlos Carrion) writes: >I write: >>>if I take a vga .GIF picture, how can I get an ega .GIF reader >>>to display the pix? I understand that the resolutions and # of bit planes >>>are different. can it be done? > I just realized what the problem is. It's not a conversion problem I >have; the problem is that I don't have a vga graphics card, so naturally my >gif reader reading a vga pix tries to enable a graphics mode that is >non-existent on my ega card. No!!!!! All you need is a GIF reader that works with the EGA. EGAGIF, PICEM, or FASTGIF are good examples. Nothing in the GIF file has any effect on what video mode the reader program uses. You are probably using VGIF or another VGA-specific reader program. At the most basic level, there is no such thing as a VGA GIF picture. It may be 320x200x256, but if you display it on an EGA you will see 320x200x16 or 640x200x16 or whatever mode you tell your reader program to use. It'll probably default to 640x350x16, but many have options. -- Mark D. Freeman (614) 262-1418 Applications Programmer, CompuServe mdf@tut.cis.ohio-state.edu [70003,4277] ...!att!tut.cis.ohio-state.edu!mdf Columbus, OH Guest account at The Ohio State University
mdf@tut.cis.ohio-state.edu (Mark D. Freeman) (09/13/88)
In <2324@ihlpm.ATT.COM> snafu@ihlpm.ATT.COM (00704a-Wallis) writes: >1) Does anyone know where I can find an archive of > GIF pictures? Anyone have any they want to trade? There are several on CompuServe. >2) does anyone have docs on the GIF format specification? In the CompuServe PICS forum, you can get information on the format. In fact, if you are interested in developing some software, I think (my own hazy recollection -- this is not a statement of company policy) you can even get a free account and access time as an aid to developing your program. -- Mark D. Freeman (614) 262-1418 Applications Programmer, CompuServe mdf@tut.cis.ohio-state.edu [70003,4277] ...!att!tut.cis.ohio-state.edu!mdf Columbus, OH Guest account at The Ohio State University
johnm@trsvax.UUCP (09/14/88)
>>1) Does anyone know where I can find an archive of >> GIF pictures? Anyone have any they want to trade? > >There are several on CompuServe. ^ thousand >>2) does anyone have docs on the GIF format specification? > >In the CompuServe PICS forum, you can get information on the format. >In fact, if you are interested in developing some software, I think (my >own hazy recollection -- this is not a statement of company policy) you >can even get a free account and access time as an aid to developing >your program. You will find the GIF developers application in Library 1 of the PICS forum. Fill it out, pester the people in charge for two weeks, and if you have any real programming experience they will grant you admission to the fold. What you get is: all time online is free WHILE YOU ARE IN PICS (which means that if GIF is all you are interested in you probably won't ever get any bills), access to Library 17 which is the GIF developer's discussion area and download library (which has lots of good source code to speed up development of your own GIF stuff, plus not yet released applications by other people). The free access time can really come in handy when you want to download 2 or 3 meg of pictures. John Munsch