Re: A follow-up on my post
Re: A follow-up on my post
- Subject: Re: A follow-up on my post
- From: Stephen Herron <email@hidden>
- Date: Thu, 30 Jul 2009 12:45:51 -0700
Hi everyone,
Brian Lawler's color management problem may become normal for
ColorSync users. The rich black result is exactly what Apple expects.
Icefields 4.1 operates in the same way, and it uses ColorSync and OS
10.5 as described by developer.apple.com. ColorSync is a color space
to color space transformation method. It does not pass through
PostScript's device spaces. (See http://developer.apple.com/technotes/tn/tn2035.html
for a diagram of this procedure.)
Here is one scheme that may happen:
The PDF encodes black as: MyriadPro 0.0/0.0/0.0/1.0, and uses
DeviceCMYK and CMYK setcolor
The PDF page may be rasterized to halftone using a method similar to
OS 10.5 Core Graphics:
CGContextDrawPDFPage(pdfCGContextRef, page);
During the OS 10.5 rasterization process, device colors are encoded in
color space (I guess the Generic CMYK model) and then a color space
conversion to the output color space occurs. There isn't an Apple
CGPDF or PDF Kit function available to obtain the embedded profile(s).
In a PostScript workflow the output color space is coded as an CSA.
If the output ICC profile is kCGColorSpaceGenericCMYK, then Icefields
converts black to 0.79/0.73/0.68/0.68 resulting in rich black. In Mr.
Lawlers case, the output ICC profile is embedded in the PDF and the
RIP appropriately uses that profile.
The only color space conversion method that would be successful at
maintaining 1.0 K is a profile with a black generation curve defining
100 % black as 0.0/0.0/0.0/1.0. Does any profile do this?
Icefields 4.1 displays the result of color space conversions, scaling
to the halftone resolution, and halftoning. It's a good thing to have
Icefields :-)
Stephen Herron
email@hidden
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