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2006.10.17 11:41 "Re: Tag 346", by Leonard Rosenthol
At 5:47 PM -0400 10/16/06, Ross Presser wrote: >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 -- --------------------------------------------------------------------------- Leonard Rosenthol <mailto:leonardr@pdfsages.com> Chief Technical Officer <http://www.pdfsages.com> PDF Sages, Inc. 215-938-7080 (voice) 215-689-3863 (fax)