(v13) Color management for simulating paper color

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

As a rule, color management as used in printing uses the relative rendering intents of RelativeColorimetric, Perceptual, and Saturation. The common feature of these intents is that an input color of white (almost always) maps to white on output (that is, no ink on the paper). It is sometimes desirable to force the use of absolute rendering intents to make the output appear to match the media white of the input media by laying down ink in the background.

The use of absolute rendering intents often gives very similar results to the simple emulation method in Simple interception of device color spaces. Indeed, with the same profiles and the colorimetric intent, the output is identical for purely /DeviceCMYK, /DeviceGray jobs. The difference is most apparent when jobs contain RGB elements where the emulation setup requires two color conversions, one in each of the emulation and proofing transforms. It may be that the double color conversion changes color unacceptably, or perhaps the emulation ICC profile does not contain the required tables for the emulation transform. In these cases, an adequate proofing configuration may be created using absolute intents. This example illustrates the additional absolute rendering intents supported by the RIP.

<<
	/DeviceRGB [ /ICCBased (iccprofiles/sRGB.icc) (r) file ]
	/DeviceCMYK [ /ICCBased (iccprofiles/SWOP.icc) (r) file ]
>> setinterceptcolorspace
<<
	/Profile (iccprofiles/Inkjet.icc) (r) file
	/IntentMappings <<
		/RelativeColorimetric /AbsoluteColorimetric
		/Perceptual /AbsolutePerceptual
		/Saturation /AbsoluteSaturation
		/AbsoluteColorimetric /AbsoluteColorimetric
	>>
>> setreproduction
<< /EraseColor {0 0 0 0 setcmykcolor} >> setpagedevice

This is similar to the simple example from (v13) Interception re-purposing of jobs for different output devices, except that each of the relative rendering intents has been replaced with its absolute counterpart.

The AbsolutePerceptual and AbsoluteSaturation intents are non-standard intents that may only be used within IntentMappings; see (v13) Rendering intent overrides.

The EraseColor setpagedevice key has been set for the same reason as emulation configurations - (see (v13) EraseColor in the page device) - to avoid obvious artifacts at the boundaries of white objects. Setting the erase color to a color managed CMYK white, as in the above example gives good results, but artifacts may still be present for

• pages containing device independent color,
• white objects painted in /DeviceRGB.

The reason for these artifacts is because the erase color has been painted using the /DeviceCMYK intercept, while other white objects in the job have been painted using a different profile with a different media white. Where such artifacts are undesirable, an emulation configuration should be used in preference, if possible; see Emulation re-purposing.