Method and apparatus for digital printing

Abstract

A method of digital printing is disclosed in which a digital image to be printed has at least one region having pixels comprising superpositioned layers of a first ink and a second ink. The method includes producing at least one sample print and calibrating misalignment of the superpositioned layers at a plurality of calibration locations on the sample print. The resultant misalignment data is provided to a morphing program to determine a pre-deformation of the digital image to compensate for misalignment during printing. An apparatus and a machine-readable storage medium comprising instructions executable by a processor are also disclosed.

What is claimed is: 
     
         1 . A method of compensating for misalignment in digital printing comprising:
 providing a digital image having at least one region having pixels comprising superpositioned layers of a first ink and a second ink; producing at least one sample print;   calibrating misalignment of the superpositioned layers at a plurality of calibration locations on the sample print; and   providing misalignment data to a morphing program to determine a pre-deformation of the digital image to compensate for misalignment during printing.   
     
     
         2 . A method as claimed in  claim 1 , wherein the morphing program interpolates the misalignment of the image between calibration locations. 
     
     
         3 . A method as claimed in  claim 1 , wherein morphing program compensates for physical deformation of the print media. 
     
     
         4 . A method as claimed in  claim 1 , wherein the morphing program applies a non-uniform deformation to the image to compensate for physical deformation occurring with respect to one or more of: image or media axis, print time and media composition. 
     
     
         5 . A method as claimed in  claim 1 , wherein the first ink layer is a white ink layer and the second ink layer is a color ink layer, the white ink layer providing an overflood or underflood for the color ink layer. 
     
     
         6 . A method as claimed in  claim 1 , wherein the first ink layer and second ink layer are printed by non-aligned print heads. 
     
     
         7 . An apparatus comprising:
 an input for receiving misalignment data from a sample print of a digital image, said misalignment data being indicative of a misalignment of a first ink and a second ink at a plurality of locations on the sample print in which pixels of both the first and second ink are formed as superpositioned layers; and   a processor to: use said misalignment data to determine misalignment across the sample print of the digital image; and determine a pre-deformation of the digital image to compensate for the misalignment in the superpositioned layers.   
     
     
         8 . An apparatus as claimed in  claim 7 , wherein the apparatus further comprises a scanner for capturing misalignment data from the sample print and providing resulting data to the sample print. 
     
     
         9 . An apparatus as claimed in  claim 7 , wherein the apparatus further comprises a digital printer and wherein the digital printer comprises at least a first print head to deliver the first ink and at least a second print head to deliver the second ink, wherein the print head to deliver the first ink and the print head to deliver the second ink are positioned in a staggered configuration relative to the print medium. 
     
     
         10 . An apparatus as claimed in  claim 9 , wherein the at least a first print head to deliver the first ink comprises a plurality of aligned color print heads. 
     
     
         11 . An apparatus as claimed in  claim 10 , wherein the print head to deliver a second ink comprises at least one white ink print head. 
     
     
         12 . An apparatus as claimed in  claim 7 , wherein the apparatus comprises a print server, the print server including the processor. 
     
     
         13 . A non-transitory machine-readable storage medium comprising instructions executable by a processor to: receive print layer alignment data related to alignment measurements of a first ink layer and a second ink layer at a plurality of locations on a sample print of a digital image; use said print layer alignment data to determine misalignment of the print layers across the sample print; and apply a morphing routine to the digital image to compensate for the misalignment of the layers across the digital image. 
     
     
         14 . A non-transitory machine-readable storage medium as claimed in  claim 13 , wherein the instructions are further executable by a processor to: interpolate the alignment of the print layers at a plurality of points intermediate to the plurality of locations; and update the print layer alignment data to include said interpolated alignment data. 
     
     
         15 . A non-transitory machine-readable storage medium as claimed in  claim 13 , wherein applying a morphing routine comprises a non-uniform pre-deformation of a white layer of the image to compensate for the misalignment identified in the sample print.