2006.10.16 20:34 "[Tiff] Tag 346", by Ross Presser

2006.10.17 11:41 "Re: [Tiff] Tag 346", by Leonard Rosenthol

The reason I asked is slightly off topic for TIFF, in fact. As you probably know, the PDF spec does support Indexed images in any colorspace defined in the PDF.

ALMOST any colorspace...You can't have indexed Indexed, indexed Pattern, indexed Separation or indexed DeviceN.

In fact, the default profile for Adobe Distiller will automatically convert *all* images in the source to indexed images as long as the total color count is less than 256.

PDF Enhancer (http://www.apago.com) will do the same thing. In addition, if the option is enabled, it will also perform quantization on RGB images with <1000 colors down to 256.

But since there are apparently *zero* raster file formats that can contain indexed CMYK images,

Photoshop supports indexed CMYK, IIRC.

it's impractical to do any image manipulation on these bitmaps.

Not at all...You just need an imaging library that supports indexed CMYK and can read a "blob"...GraphicMagick, for example, springs to mind. You could also use Adobe's new open-source GIL. Or you could write your own.

I am considering writing a custom tool that converts them to RGB palette on the fly, and back again.

4->3->4 color conversion is a BAD IDEA!! As the numbers demonstrate, you will LOSE information (even with ICC-based color conversion).


Leonard Rosenthol                            <mailto:leonardr@pdfsages.com>
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