[cups] some IPP attributes don't work for some printers

Michael Sweet msweet at apple.com
Wed Sep 9 12:44:45 PDT 2015


Jacob,

> On Sep 8, 2015, at 7:39 PM, Jacob Marble <jacobmarble at google.com> wrote:
> 
> A PPD for a particular color printer lacks a ColorModel entry, but CUPS
> indicates that color printing is possible with:
> 
> color-supported=true
> print-color-mode-default=color
> print-color-mode-supported=color,monochrome
> 
> So, instead of printing with the ColorModel attribute, I use
> print-color-mode=monochrome. But. Color comes out of the printer.
> 
> Digging into other PPD entries, I found this attribute, which *does*
> control color vs monochrome in print tests:
> *OpenUI *CMAndResolution/Print Color as Gray: PickOne
> 
> Looks like this occurs in a dozen or so HP printers, out of my collection
> of about 7000 PPDs from multiple manufacturers.
> 
> How does CUPS decide that this printer should have the print-color-mode
> attribute? Is this a bug in CUPS or in the PPD?

The PPD.

CUPS looks for the ColorDevice keyword in the PPD, and uses that to determine what values of the print-color-mode attribute  are supported.  CUPS supports the standard ColorModel plus a handful of non-standard keywords that directly map to it for applying the print-color-mode value, but *not* CMAndResolution (which by its name is likely a non-standard combination of ColorModel and Resolution...)

_________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair




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