Message-Id: <mailto:199501091627.KAA05389@library.wustl.edu> Date: Fri, 6 Jan 1995 17:59:57 -0500 From: "mailto:Walter_Gilbert@UMAIL.UMD.EDU--Maryland" <WALT@UMDD.bitnet> Subject: Re: Is GIF on the ropes? To: Multiple recipients of list IMAGELIB
On Thu, 5 Jan 1995 19:03:37 CST Pete Bergstrom said: >>>>>> On Wed, 4 Jan 1995 13:35:54 -0500,
>"mailto:Walter_Gilbert@UMAIL.UMD.EDU--Maryland
>" <mailto:WALT@UMDD.BITNET> said:
>> Thanks to Kurt Foss for the warning about .GIF format. We should all
>> switch to PKZIP, the generic compression software. It does a better job
>> of compressing than .GIF does.
>
>Hmm.
>
>How did you come to this conclusion? On what subject matter does PKZIP do
>"a better job of compressing than .GIF"? In what encoding do you suggest
>storing images such that pkzip compression may be useful? You were speaking
>of images, right?
>
>Pete
I took five "random" 768x1024-pixel .BMP full color images and converted them to .GIF and also compressed them with PKZIP. In 4 of the 5, the PKZIP compression was 5% to 10% better (the files were smaller); in one case, they were virtually the same size. (The original bit-mapped images were uncompressed.) A sixth image, a B&W line drawing with one "color" plane was 49K in .BMP, 5,781 in .GIF, and 4,338 in .ZIP.
Of course, I'm only half serious in this. In a .ZIP compression, the header information is not readily available; it would have to be decompressed to learn anything about the image. However, it does show that the compression scheme so cherished by Unisys and CompuServ is not very good.
If I were to recommend an alternative, I would suggest compressed .BMP: (yes, .BMP does include a compression alternative, the Windows logo image is reportedly a compressed .BMP file). It is simple and therefore would admit fast decompression. ALSO: .BMP supports 24-bit color while .GIF is limited to 8-bit color. ANOTHER GOOD REASON TO ABANDON .GIF! Walt
Walter Gilbert, Asst. Dir. mailto:Walter_Gilbert@umail.umd.edu Computer Science Center Manager: Teaching Technologies University of Maryland at College Park 20742-2411 (301)405-6727