The Persistence of Vision Raytracer (POV-Ray).

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Attached to Project: POV-Ray
Opened by Christoph Lipka - 2010-04-27
Last edited by Christoph Lipka - 2010-08-29

FS#103 - JPEG output does not conform to baseline JFIF standard

POV-Ray 3.7-generated JPEG image output files do not conform to the JFIF standard. Most importantly, the files written do not use the standard YCbCr color model (they seem to use plain RGB instead), nor do they have a proper JFIF tag.

As a consequence, some software may be unable to read the generated JPEG files properly. In addition, it seems that POV-Ray mixes up the Red and Blue channels.

Closed by  Christoph Lipka
Sunday, 29 August 2010, 20:09 GMT
Reason for closing:  Fixed
Christoph Lipka commented on Tuesday, 27 April 2010, 16:17 GMT

fix submitted as change #4956

Thorsten Fröhlich commented on Wednesday, 28 April 2010, 17:12 GMT

This color swap is a bug indeed, but the RGB output is not. IIRC not having a plain JFIF tag is a requirement for some software to grasp that the encoded image is RGB rather than YCC. Using RGB has several benefits over a YCC for ray-traced images that have sharply defined object borders, a traditional weakness. While more pronounced with reduced chroma resolution of the default 4:2:0 sampling used by most JPEG software, even with 4:4:4 sampling the artifacts remain.

Grimbert Jérôme commented on Monday, 09 August 2010, 12:10 GMT

Jpeg output with beta38 (from source) is ok regarding the displayed colours.
No problem to display the native jpeg with imagemagick.


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