hutch@sdcsvax.UCSD.EDU (Jim Hutchison) (04/20/87)
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more color.
Has anyone considered more color? During the recent Amiga ray-tracing/color
article landslide, I noticed a cry for 24 bits instead of 12. (The Amiga
folks realized that they might need bigger screens, so you can scroll bitmaps
larger than the screen (fast). This is just a sidebar)
So now what about higher color quality? I have heard that film can take as
many as 40-50 bits of color. Well? Guess I get to make 6 passes on the QCR.
How to do it though? A pass of 24, 24, and XX?
--
Jim Hutchison UUCP: {dcdwest,ucbvax}!sdcsvax!hutch
ARPA: Hutch@sdcsvax.ucsd.edu
Disklame'r:
One greater than the greatest signature representable with 184 symbols.hedley@cbmvax.cbm.UUCP (Hedley Davis) (04/22/87)
<munch> hutch@sdcsvax.UCSD.EDU (Jim Hutchison) writes: > >Has anyone considered more color? During the recent Amiga ray-tracing/color >article landslide, I noticed a cry for 24 bits instead of 12. > Yep, you bet. We have a 'planned' expansion path for the architecture which does include better color. However, other enhancements are in line before we get to this one. So do not hold your breath. Also keep in mind that the Amiga is primarily an NTSC video box, not a film box. I'm sorry, but if you want Lucasfilm quality, you'll have to go elsewhere. As a breif aside, you should look at the '83 SIGGRAPH proceedings which contains a ( now classic ) article describing color compression in images. The article deals with the 'Median Cut' algolrithm for color table entry allocation. Very impressive two bit per pixel color images are presented. If you use the techniques in this article, and the hold and modify mode of the amiga, you can acheive surprising results. Sure this is compute intensive, but it can give you some of the best results I've ever seen on an Amiga. Hedley
lmiller@venera.isi.edu (Larry Miller) (04/23/87)
In article <1709@cbmvax.cbmvax.cbm.UUCP> hedley@cbmvax.UUCP (Hedley Davis) writes: ><munch> > >As a breif aside, you should look at the '83 SIGGRAPH proceedings which >contains a ( now classic ) article describing color compression in >images. The article deals with the 'Median Cut' algolrithm for color >table entry allocation. Very impressive two bit per pixel color images >are presented. > >If you use the techniques in this article, and the hold and modify mode >of the amiga, you can acheive surprising results. Sure this is compute >intensive, but it can give you some of the best results I've ever seen >on an Amiga. > >Hedley Here is a citation (in refer format) to another article by the same author, describing the technique. I've implemented this on 24 bit/pixel digitized maps on an IRIS, reduced to 4 bits per pixel. The results, however, were not too good. It was necessary to change the algorithm somewhat to allow for very low frequency shades being retained in the image (lat/long lines, for example). Larry Miller lmiller@venera.isi.edu --------------------------- CUT HERE --------------------------------- %A Paul Heckbert %T Color Image Quantization for Frame Buffer Display %J Computer Graphics %D July, 1982 %V 16 %N 3 %P 297-307 %K Graphics, Dither, Color images %X Presents a method for selecting the N best colors to represent an image digitized at M (M >> N) colors. The methods presented are ``uniform quantization'' and ``median cut.'' In uniform quantization, the N most frequent colors are selected. Median cut uses an adaptvie algorithm to find the N ``best'' colors, and generally produces better results. Typical quantization levels are eight bits per pixel. Dithering also increases the quality of the final images.