Picture processing apparatus

Claim 1

A picture processing apparatus for processing images, comprising: a register storing one or more different tone patterns, each of which has a different starting address and each of which is comprised of a plurality of digital numbers stored in sequential addresses within said registers, said digital numbers used for establishing comparison thresholds, some of said different tone patterns being intended for use in processing binary tone level images and some of said different tone patterns being intended for use in processing multilevel tone images, said register having a digital output at which at least one of said digital numbers from a tone pattern stored therein appears, and having an address input for receiving an address which controls which of said digital numbers appears at said output; an address decoder having an address output coupled to said address input of said register, for supplying address data to said register and having a picture processing data input for receiving picture processing data which said decoder decodes to generate starting address data for supplying to said register via said address input, and having a clock input for receiving a clock signal which causes the address appearing at said address output of said address decoder to be incremented synchronously with said clock signal thereby causing different ones of said digital numbers stored in said register to appear at said digital output of said register; a central processing unit having a picture processing data output coupled to said address decoder and a data output coupled to said register, said central processing unit for determining if an image to be processed is a binary tone level image or a multilevel tone image and, if said image to be processed is a binary tone image, for supplying picture processing data to said address decoder for decoding therein into a starting address for a tone pattern for binary tone images in said register, and, if said image to be processed is a multilevel tone image, for supplying picture processing data to said decoder for decoding therein into a starting address in said register for a multilevel tone pattern; a background color compensator having an input for receiving an analog picture signal derived from said image being processed, and having an output at which a first positive reference signal appears; a source for supplying a second, fixed-level positive reference signal; a selector switch means having a first input coupled to receive said first positive reference signal, a second input coupled to receive said second, fixed-level positive reference signal, and having an output at which a positive reference current signal appears, and having an input for receiving a binary/multiple level tone pattern selection signal, said selector switch means for selecting either said first positive reference signal or said second, fixed-level positive reference signal for conversion to said positive reference current signal in accordance with the state of said binary/multiple level tone pattern selection signal and for presenting said positive reference current signal at said output; a source for supplying a fixed level negative reference current signal; a digital-to-analog converter having an input coupled to said digital output of said register for receiving said digital numbers appearing at said digital output of said register in synchronization with said clock signal, and having a positive reference signal input coupled to receive said positive reference current signal, and having a second input for receiving said negative reference current signal, and having an analog output at which an analog signal appears the magnitude of which is determined by the value of said said digital output of said register, the magnitude of said positive and negative reference current signals establishing the dynamic range of said analog signal appearing at said analog output; a current/voltage converter having an input for receiving said analog output signal from said digital-to-analog converter and having an output at which a comparison threshold voltage signal appears, the magnitude of which is derived from the magnitude of said analog signal output by said digital-to-analog converter; a comparison calculator having an input coupled to receive said analog picture signal derived from said image being processed, and having an input for receiving said threshold voltage signal from said current/voltage converter, said comparison calculator for comparing said analog picture signal derived from said image being processed to said threshold voltage signal and for generating a digital output signal which digitally encodes the image being processed.