[Openicc] JFIF, SPIFF and CMYK + ICC Support

[Michael Sweet]

Jan-Peter,

You might also want to look at Exif which defines the subset of JPEG (and JFIF) used for digital cameras (addresses the simple sRGB vs. AdobeRGB color space choices):

	http://www.cipa.jp/english/hyoujunka/kikaku/pdf/DC-008-2010_E.pdf

and the Sun/Oracle specification for embedding ICC profiles in JPEG/JFIF files:

	http://docs.oracle.com/javase/6/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html

In my experience from doing the CUPS image support, at least some versions of Adobe apps write CMYK images as JFIF files with the color information converted to RGBW (via simple inversion).  Applications that support CMYK JFIF files have to go through hoops to determine whether the Adobe APPn chunk is present in the JFIF file and adjust the color values accordingly.


On 2012-10-10, at 4:45 AM, Jan-Peter Homann <homann at colormanagement.de> wrote:
> Hello list,
> During working on book project, I´m doing a research about fileformats and the supported colorspaces incl. embedding of ICC-profiles.
> 
> From the enduser perspective, photoshop offers to save images in the "JPEG-Format" supporting RGB and CMYK with embedded profiles.
> 
> Googling the Specs I found, thet JPEG is mainly a compression and fileformats are another case.
> 
> I found the JFIF specification, which can be uses for RGB-images only and encodes color internally as YCC.
> I also found part 3 of the JPEG specs, which introduces additionales color spaces and the SPIFF File Format.
> 
> If anybody could please comment or correct following statements:
> 
> - If CMYK images are stored as "JPEG-File", it means that a SPIFF conforming file is created
> - The standard-format for saving JPEG compressed RGB images is JFIF
> - SPIFF also allows to store RGB-images with embedded ICC-Profile, but this seldom used in daily practice
> - An application, which can handle both RGB and CMYK JPEG compressed images, supports normally JFIF and SPIFF
> 
> Thanks for the help
> Jan-Peter
> 
> 
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__________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair