Tech Info 091: JPEG compressed RGB-TIFF images lead to bad output

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HELIOS Tech Info #091

Fri, 04 Nov 2005

JPEG compressed RGB-TIFF images lead to bad output

Adobe PhotoShop does support JPEG compressed TIFF images. For the RGB colorspace it does save a YCbCr based image which is not supported by ImageServer UB.

There are error messages like:

> [tom:demovol] oiimginfo -Ebase RGB-JPEG-TIFF.tif 
> Cannot open file `/Volumes/PlatteII/demovol/RGB-JPEG-TIFF.tif'. 
> ...
> [11] Missing required TIFF tag: YCbCrCoefficients (HeliosTiff)
The upcoming ImageServer update u0503 will add basic support for those images and there is no longer an error message:
> [tom:demovol] oiimginfo -Ebase RGB-JPEG-TIFF.tif 
>       Image type:            TIFF
>       Compression:           JPEG
>       Rows:                  960
>       Columns:               1280
>       X resolution:          288.000000 dpi
>       Y resolution:          288.000000 dpi
>       Colorspace:            YCbCr 
>       Number of channels:    3
Still those images can not be used since the color conversion (for layout generation and final output) does lead to poor results as the image RGB ICC-profile is not accepted by ImageServer for a YCbCr based colorspace.
This problem will be solved in a future ImageServer version or an update. When it is available, this information will be distributed by a follow up to this Tech Info.
As a workaround it is possible to convert such a YCbCr based image to RGB via ImageServer, e.g.:
layout -o PrintColor=RGB -l SourceImage.tif "{unix,native,,TIFF}ConvertedImage.tif"
The converted image does now work properly.