Color Space on Thumbnail Image Variants

Hi all-
I'm loading some CMYK images into my repository (5.5 SP05) and trying to use the default thumbnail variant in a web application. For some reason, even though the color space of the thumbnail is set to RGB, it doesn't get converted when the thumbnail is created. This results in a .jpg that is CMYK (and isn't understood by a browser).
If I create a custom variant as .jpg and of the RGB color space, it works fine after generation. Is this a bug? Or is there a way to force the generation of thumbnails? I was trying to not have too many variants in my repository because I was worried about bloating it. Perhaps this shouldn't be a concern, but it still seems as if the thumbnail should get converted to RGB according to the settings in the Console. Any thoughts?
Thanks
Tim

Tim,
Sounds like this may be a bug. Since the Thumbnails are set to RGB, and cannot be changed, it seems as though they should be generated in RGB color space.
One thing to try. Go into the images table, right click on an image in the records window, and select Generate Thumbnail. I believe it will actually regenerate the thumbnail. Maybe this will regenerate with the RGB color space. That's my only idea. Other than that you really don't have much control over the thumbnails.
Regards,
Tim

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Please note, I understand that it's not an actual JPG file, that the data is only using the compression scheme.

DCTDecode is entirely legal for 1-component (greyscale) samples as you've noted. There is no problem there.
Remember, that applying a filter (and later decoding it) is entirely separate from the meaning of the data. So it's possible to use filters that just don't map correctly to the data. For example, greyscale DCTDecode could be used to encode samples which were, on decoding, to be treated as RGB. It wouldn't compress well, but the meaning isn't affected.
But DCTDecode for an Indexed colour space is very unusual. Don't look for special treatment, it would be enconding the image data, which would be offsets into the colour table. And of course DCTDecode is lossy, so decompressed data should be close, but is not always equal, to the original.
In most cases of Indexed colour, this would lead to random and useless changes to colours. But it is entirely possible to have colours which map into a linear and smooth set of shades of the same colour - such as 256 shades of pink. An image using such an Indexed colour space is a candidate for using DCTDecode.
In using filters, it is best to forget what you think you know about the data, and just follow the precise rules of the filter.

Color Space on Thumbnail Image Variants

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