Piece-wise print image enhancement for dot matrix printers

Apparatus for enhancing the displayed image produced by a display apparatus, said display apparatus including character generator means providing a bit data signal representative of a bit map image of a desired image and image display means responsive to said bit data signal to display said desired image, said apparatus comprising:

• temporary storage means coupled to said character generator temporarily storing portions of said bit data signal representing N number of consecutive bits in M number of consecutive lines of said bit map image forming an M x N subset of the bits defining said bit map image, a predetermined number of bits of said subset of bits forming a sample window having a predetermined shape defined by the matrix position of said bits, said sample window having a central bit;
• matching network means coupled to said temporary storage means for comparing the bit pattern formed by said central bit and the remaining, adjacent bits in said sample window with a plurality of predetermined error matching bit patterns, each of said matching bit patterns associated with one of a plurality of modification signals;
• and
• signal generating means coupled to said matching network means and to said image display means for generating an associated one of a plurality of predetermined modification signals if said sample window bit pattern matches at least one of said plurality of error matching bit patterns, said associated modification signal substituted for said central bit in said bit data signal, said image display means responsive to said modification signal to display a modified image element associated with said central bit.

An electrophotographic printing machine comprising:

• rotatable drum means;
• a layer of photoconductive material mounted on the surface of said rotatable drum means for cyclic movement through electrophotographic process stations;
• charge corona means disposed adjacent said rotatable drum means for placing a substantially uniform electrostatic charge on the surface of said layer of photoconductive material;
• exposure means for selectively discharging said charged photoconductive material to cause the formation of a latent image on the surface of said photoconductive material;
• developer means disposed adjacent said rotatable drum means for applying toner to said latent image to produce a developed image;
• transfer means disposed adjacent said rotatable drum means for transferring said developed image from said photoconductive material to a print media;
• fusing means for fusing said toner to said print media;
• paper transfer means for serially moving said print media from a media storage means through said transfer means to said fusing means;
• control means for operating said exposure means;
• character generator means coupled to said control means to provide data signals representative of a desired image to be produced on said photoconductive material;
• and
• enhancement means interposed between said control means and said character generator means for generating compensation signals to be substituted for selected ones of said data signals whereby an image produced from said substituted data signals is of an enhanced visual quality, said enhancement means comprising:
• temporary storage means coupled to said character generator means temporarily storing portions of said data signals forming a sample pattern representative of a portion of said desired image, said sample pattern having a central data signal;
• matching networks means coupled to said temporary storage means for comparing said sample pattern to a plurality of predetermined template patterns, each of said predetermined template patterns associated with one of a plurality of compensation signals;
• and
• signal generating means coupled to said matching network for generating said associated one of said plurality of compensation signals if said sample pattern matches at least one of said predetermined template patterns said associated compensation signal substituted for said central data signal in said data signals.