[pdftex] jpeg <-> png (was: Best bitmap image format?)
hartmut_henkel at gmx.de
Sun Feb 26 22:24:03 CET 2006
On Sun, 26 Feb 2006, Martin Schröder wrote:
> <quote src="http://www.faqs.org/faqs/jpeg-faq/part1/">
> Adobe Photoshop and some other prepress-oriented applications
> will produce four-channel CMYK JPEG files when asked to save a
> JPEG from CMYK image mode. Hardly anything that's not
> prepress-savvy will cope with CMYK JPEGs (or any other CMYK
> format for that matter).
> If you really want cmyk, you need tiff.
Modern viewers don't have problems with cmyk-jpeg or embedded cmyk-jpeg,
e. g. current xpdf, adobe reader, gs, display, xloadimage show it (but
colors on screen differ considerably).
Regarding the above quote, the PDF viewers naturally don't have any
problems with vectors drawn or filled in CMYK colors.
Unfortunately cmyk-jpeg files have about triple file size compared with
normal jpegs, seems that the four components are compressed completely
independently from each other.
Yes, pdftex can embed cmyk-jpeg without problems. E. g. we have to use
it, as cheap internet print shops often require cmyk-jpeg input instead
of PDF, even for flyers with text (set to best quality!), as this
cmyk-jpeg is the least troublesome format --- for them: the customer has
to care for the dimensions by providing the right x*y number of pixels
at the density given by the shop, the shop doesn't need to care for
(maybe missing) fonts, no risk for them to be guilty of wrong colors or
size, they just dump the unscaled CMYK to the printer.
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