On 26.04.2010 21:08, clipka wrote:
> There are still issues though: While IC displays the JPEG output images
> as expected, Windows Explorer preview and Photoshop 6.0 get the RGB
> values wrong way round (i.e. blue displays as red and vice versa). So
> given that IC normally does a pretty good job at JPEGs, POV-Ray must be
> doing something pretty unconventional there.

In fact IC swabs the red and blue channels (and therefor shows POV-Ray 
jpeg images correctly) BECAUSE POV-Ray is doing it wrong by storing BGR 
instead of RGB.
POV-Ray is the one and only application that I am aware off that does 
not perform the RGB to YCbCr color space transformation but uses the DCT 
directly on RGB, err in this case BGR data. This is perfectly legal for 
jpeg (when done in the right order of channels) but does not make much 
sense because it results in either more pronounced block artifacts or 
larger file size.

My suggestions for writing ray-traced jpeg files would be anyway:
- use YCbCr
- no chroma sub-sampling (to avoid the disappearance of small red or 
blue colored details)
- compression setting of 85%

in my experience (and I did a lot of tests on that matter) this gives 
the best trade-off between quality and file size.


On a different matter: adding the render statistics as a metadata tag to 
PNG would be very nice. And doing the same with OpenEXR even more nice 
as OpenEXR is the format I do use as default file format for all my 
POV-Ray work.

-Ive

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