BINARIZING METHOD AND DEVICE FOR MULTILEVEL IMAGE

PURPOSE:To attain the high speed of a processing, to simplify a circuit, and to constitute a device at a high speed and at a low cost without deteriorating a halftone image by changing a threshold value in each main scanning line, and making equal the difference of the threshold values in the adjacent main scanning lines. CONSTITUTION:A picture input 1 is temporarily stored in an input buffer memory 2, and read by each picture element. The error data of the processed picture elements are added to the picture element by an adder 3, and inputted to a comparator 5. The threshold value is read from a threshold value memory 12 by each line by a line synchronization control circuit 13, and set. The threshold values obtained by making equal the difference of the threshold values in the adjacent main scanning lines are preliminarily stored in the memory 12. Then, the threshold value is compared with the input data by the comparator 5, and the binarized output is stored in an output buffer memory 9. The difference of the data inputted and outputted by the comparator 5 is calculated as an error by a computing element 6. The error is delayed for one picture element by a delay circuit 11, multiplied by a weighting factor by a weighting circuit 7, and inputted to the adder 3. The error is delayed for one picture element, and added to the next picture element by the adder 3.