Patent ID: 11956402
Assignee: HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 14:
15. Non-transitory machine readable medium according to claim 14, storing further instructions which, when executed, cause a processor to:
derive a halftone threshold matrix from the greyscale image having a first number of grey levels wherein the greyscale image has non-binary sub-pixel resolution, wherein each non-binary sub-pixel is associated with a grey level;
wherein deriving the halftone threshold matrix comprises:
increasing the number of grey levels in the image to the second number of grey levels by:
determining a grey level of a non-binary pixel based on the average of the grey levels of the non-binary sub-pixels of each non-binary pixel;
determining a target number of non-binary sub-pixels per grey level based on the number of non-binary sub-pixels and the second number of grey levels;
taking the non-binary pixels in pixel order, allocate a grey level of the second number of grey levels to each non-binary pixel to provide, on average, the target number of non-binary sub-pixels per grey level; and
deriving a threshold value for each non-binary sub-pixel which is proportional to the grey level of the non-binary sub-pixel; wherein
the halftone threshold matrix comprises the threshold values for the non-binary sub-pixels.