Transfer functions and halftones

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

Some halftone dictionaries can have a TransferFunction entry. [RB3] says that TransferFunction “overrides the transfer function specified by settransfer or setcolortransfer”. Likewise, [PDF2] says it "shall override the corresponding one specified by the current transfer function parameter in the graphics state". However, the RIP applies both by default. There is a user parameter UseAllSetTransfer to provide for strict compatibility (see Order of application of calibration and transfer functions); however, we believe that because jobs use settransfer and setcolortransfer it is not reasonable to suppress this just because a halftone is set with a TransferFunction entry, and that unintended effects could be caused by direct application of the manual’s definition.

Also, the TransferFunction entry in halftone dictionaries has been extended. As well as the standard types, a literal array or a dictionary can also be given. Literal arrays are interpreted as interpolation arrays (see Calibration array details). Dictionaries represent PS functions.