Antipatterning printmode for matrix-based scattered-dithered images in incremental printing

This invention relates generally to machines and procedures for printing text or graphics on printing media such as paper, transparency stock, or other glossy media; and more particularly to a scanning machine and method that construct text or images from individual ink spots created on a printing medium, in a two-dimensional pixel array. Thermal-inkjet printers and processes are of greatest interest. Apparatus defines a dither mask (DM) and printmask (PM) with corresponding dimensions. In one invention form the DM dimension is not an integral factor or multiple of the PM dimension. The two dimensions may be lengths or widths; preferably the apparatus manages both; the corresponding dimensions differ by at least three pixels, and by a multiple of two pixels-more preferably eight or a multiple of eight. Preferably one dimension is an integral multiple of 256 pixels differing by eight pixels from the other. Another invention form has a scanning printhead making multiple passes across a print medium to form swaths of marks, a mechanism to define an offset smaller than at least one of the two dimensions, and a unit to index one mask by that offset between forming of successive swaths. This is valuable if DM and PM are established by preprogrammed circuits (e.g. an ASIC) or algorithms and one dimension is fixed at an integral multiple or factor of the other, with the system being practically incapable of small (or any) changes in the dimensions. Another invention form is a print method that establishes and operates a rendition stage using a DM-and a PM stage using a PM.