[cups.general] How to print image in DeviceN space?

[John Labovitz]

Thank you for the quick & detailed response.

It sounds like your suggestion of interfacing with Gutenprint to generate a raw file is my best option for the moment.  I'll start taking a look at their developer's documentation to see how to do this.

Thanks again,
--John


On 18 Apr 2011, at 1:03 PM, Michael Sweet wrote:

> On Apr 18, 2011, at 11:50 AM, John Labovitz wrote:
>> ...
>> What I'm stuck on is how exactly to get that data to CUPS so it will not be filtered through the usual adjustments and internal conversions and separations.  It seems that the DeviceN colorspace is a big part of this, but I'm still fuzzy on how this works.
> 
> There is no general way to do this, however if you pair your application with specific drivers (e.g. Gutenprint) you can generate and submit a CUPS Raster file suitable for the given printer driver - CUPS will simply pass it to the driver which will do the dithering, etc. needed.
> 
>> In looking at the CUPS documentation & code, I can see a few ways of doing this:
>> 
>> 	1. Send a multi-channel TIFF file (ordered by inks as specified in the PPD file) into CUPS using some magic options that select a DeviceN colorspace.  I haven't tried this, but I don't see any evidence that it would actually work.
> 
> It won't.
> 
>> 	2. Using the CUPS raster API, generate my own raster data from the TIFF file, using 8 or 16 bits per color and outputting the pixels pretty much as found in my separations file (ordered one of the cupsColorOrder values).  However, it appears from looking at 'imagetoraster' that dithering to 1- or 2-bit data is required?
> 
> No, it is up to the driver to tell the RIP (filter or application) how it needs the data. Look at cupsRasterInterpretPPD - it will interpret the commands in the PPD file and give you a CUPS Raster page header containing the right values.
> 
>> ...
>> I'm running OS X 10.6, with the stock CUPS, although I'm happy to build & install later versions.  The printers I'm working with are the Epson R2400, 4000, and 7500, with either the stock Epson drivers or the Gutenprint drivers.
> 
> 
> The stock Epson drivers only support RGB (and typically, sRGB). There is no way to have them utilize a DeviceN colorspace.
> 
> Gutenprint has some preliminary support for the kinds of things you want, although I don't know whether Robert has added support for the DeviceN colorspaces yet. Gutenprint also can be called directly to generate printer-ready data from a DeviceN input, so I think that will be your best option today. The print data sent to CUPS would be tagged as "raw" (application/vnd.cups-raw).
> 
> ________________________________________________________________________
> Michael Sweet, Senior Printing System Engineer, PWG Chair
> 
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