ONES COUNTING CIRCUIT, UTILIZING A MATRIX OF INTERCONNECTED HALF-ADDERS, FOR COUNTING THE NUMBER OF ONES IN A BINARY STRING OF IMAGE DATA

In an imaging system (5310), a histogram of images may be made by counting the number of "one" pixels in a matrix of image pixels. A ones counting circuit (5320) is provided to produce a binary number Y indicative of the number of "ones" in an input binary string X. The circuit (5320) comprises a matrix (5424) of counting cells (5426) arranged and interconnected in rows and columns. Each of the counting cells (5426) includes an AND gate (5428) coupled to an exclusive-OR (XOR) gate (5430). A binary string having X.sub.N bits may be thus counted employing a matrix having M rows, where M=log2(X.sub.N +1) rounded up to the nearest integer and N columns. An alternative embodiment employs a minimized matrix. This minimized matrix has M rows, where M=log2(X.sub.N +1) rounded up to the nearest integer. The minimized matrix has N=X.sub.N -2.sup.r elements in each row, where r is the row number ranging from zero for the first row to (M-1) for the last row.