Abstract: A conventional word organized random access memory is modified for image processing operations so that the pq image points of any 1 .times. pq, pq .times. 1 or p.times.q subarray of an rp .times. sq or smaller image array stored in the memory can be extracted or updated in a single memory cycle. The invention contemplates pq + 1 memory modules labeled from 0 to pq for storing the image points, each module being capable of storing rs points in distinguishable cells, only one cell of which is randomly accessible in a single instant of time. The invention further contemplates accessing circuitry for causing each image point I(i,j) of an image array to be routed to or from a memory module M(i,j) according to the relative M(i,j) =(iq+j)//(pq+1), where the notation "//" denotes the remainder resulting from integer division. The accessing circuitry additionally causes image point I(i,j) to be stored into or retrieved from a cell location A(i,j) of module M(i,j ) according to the relation A(i,j)=(i/p)s + (j/q).

Abstract: Apparatus for converting the codewords of variable-length minimum-redundancy codes into corresponding fixed-length characters. The conversion process employs a two-step mapping wherein a codeword is first converted into a fixed-length integer, and then the integer is used to index a table of fixed-length characters. The apparatus for achieving this two-step mapping comprises table storage, summation circuitry, compare/combine circuitry, and control circuitry. The table storage holds two tables, a first table containing the fixed-length characters and a second table whose values uniquely identify the variable-length code. The compare/combine circuitry and the summation circuitry accept as input the successive bits of a codeword to be converted into its corresponding fixed-length character. As the successive codeword bits are received, the summation circuitry operates on elements of the second table to calculate successive values of a weighted sum and an unweighted sum.

Abstract: A conventional word organized random access memory is modified for image processing operations so that the pq image points of any 1 .times. pq subarray, any pq .times. 1 subarray, or any regularly-spaced p .times. q subarray of an rp .times. sq or smaller image array stored in the memory can be extracted or updated in a single memory cycle. The invention contemplates pq memory modules labeled from 0 to pq-1 for storing the image points, each module being capable of storing rs points in distinguishable cells, only one cell of which is randomly accessible in a single instant of time. The invention further contemplates accessing circuitry for causing each image point I(i,j) of an image array to be routed to or from a memory module M(i,j) according to the relation M(i,j)=[iq+(i/p)//q+j]//pq, where the notations "/" and "//" denote, respectively, the quotient and the remainder resulting from integer division.

Abstract: Apparatus for encoding ordinary run-length codes and run-length codes that have been extended to include two classes of code words, regular code words for runs and special code words for selected special situations. The encoder comprises table storage, select/combine circuitry, and shift-out circuitry. The table storage holds four small tables whose values can be adjusted to correspond to any ordinary or extended run-length code to be implemented. The select/combine circuitry accepts as input a binary value that uniquely identifies the desired code word, and combines this binary value with selected table values to calculate the desired code word. The code word bits are then outputted sequentially by the shift-out circuitry.

Abstract: A conventional word organized random access memory is modified for image processing operations so that the pq image points of any 1 .times. pq or p .times. q subarray of an rp .times. sq or smaller image array stored in the memory can be extracted or updated in a single memory cycle. The invention contemplates pq memory modules labeled from 0 to pq-1 for storing the image points, each module being able to store rs points in distinguishable cells, only one cell of which is randomly accessible in a single instant of time. The invention further contemplates accessing circuitry for causing each image point I(i,j) of an image array to be routed to or from a memory module M(i,j) according to the relation M(i,j)=(iq+j)//pq, where (iq+j)//pq is the remainder resulting from the integer division of (iq+j) by pq.