IMAGE READING METHOD, IMAGE READER AND IMAGE PROCESSOR

摘要

PROBLEM TO BE SOLVED: To binarize an image in a stable way by obtaining both lowest and highest density values of an image recorded on a medium, calculating the ratio of frequency of the lowest density value to that of the highes density value, and then deciding a threshold level for the binarization processing in accordance with the calculated ratio. SOLUTION: The image data equivalent of a signal line which are hold by a line data holding part are transferred to a density histogram generation part. The density histogram generation part discriminates the density of each pixel of the inptu image data and generates a density histogram distribution of an image equivalent to a single line from the discriminated density value. A threshold generation part calculates the highest density peak value showing the white of a background and the lowest density peak value showing the black of a character from the density histogram distribution, obtains the ratio of the obtained highess density peak value to the minimum density peak value and decides a threshold level from the ratio to send it to a binarization part. The binarization part binarizes the line data which are transferred from the line data holding part.