In article <40ec4311@news.povray.org>, Warp <war### [at] tagpovrayorg> 
wrote:

>   Being a lossless image format PNG can't compete with JPEG in compression
> when storing photographs or other similar images. It can only compete
> with line-drawing-type images, cartoony images (which don't have color
> gradients) and such. Also if the image can be represented well with 256
> colors then a 256-color png can often compete with a jpg (but not always).

However, for intermediate images during processing, the lossless 
compression and 16 bit depth available in PNG make it far superior to 
JPEG. I usually render to 16 bit PNG, I can reduce it later if 
necessary, and the extra precision is useful for any post adjustments.

However, my preferred format is actually TIFF...LZW compressed TIFF has 
performed better than PNG in my tests. The Unisys patents have expired, 
leaving only the patent belonging to IBM, which from what I've read 
doesn't apply to image formats. (Correct me if I'm wrong here...but in 
any case, *that* patent's going to expire soon as well. If IBM did try 
to push it for some insane reason, they wouldn't get much benefit out of 
it.)

Anyway, aside from the compression, TIFF supports an arbitrary number of 
channels, image layers, floating point and logarithmic encodings in 
several levels of precision, and many more features.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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