PICTURE DATA PROCESSING METHOD AND PROCESSOR THEREFOR

PROBLEM TO BE SOLVED: To hide a code corresponding to optional information into compressed data without substantially deteriorating a picture by substituting respective frequency functions to which density data of respective picture component elements is converted with a specified value, and then executing quantization. SOLUTION: The four corner areas of the picture are adoped as code concealing positions. In a step 3, when the selected area is positioned at the four corners of the picture, a density data function e (x, y) in the area is DCT- converted (step 7) into a function E (x, y) with respective 64 frequencies in eight-row and eight-column as a variable. Then only the value E (8, 8) in the highest frequency coordinate (8, 8) is substituted with the product of the configuration value of the previously set code to be hidden and quantization step width w (8, 8) in the highest frequency coordinate (8,8). The frequency function E (x, y) is quantized (step 9) and the number of quantums is binarized so that the compression of density data of one area positioned at the four corners of the plane picture is completed (step 10).