RECONSTITUTING PROCESS METHOD FOR SECONDARY DIFFERENTIAL VALUE IMAGE, OUTLINE EMPHASIZING PROCESS METHOD BASED UPON SAME, AND THERMAL PRINTER BASED UPON SAME OUTLINE EMPHASIZING PROCESS METHOD

摘要

PROBLEM TO BE SOLVED: To correct a blur of a source image and to form a sharp outline image by substituting a secondary differential value at a position moved from a pixel of interest by arbitrary width as a secondary differential value positioned at the pixel of interest. SOLUTION: Primary differential values and secondary differential values of respective pixels of interest of a read-in source image are found from a calculation expression and the source image is scanned horizontally and vertically to find a couple of pixels which both secondary differential values larger than a threshold value and have primary differential values with the same sign, thereby extracting an outline (ST1). Then secondary differential values at positions moved by arbitrary width from the pixels of interest in two normal directions to the tangents to respective pixels of interest on the outline are substituted as secondary differential values positioned at the pixels of interest to reconstitute a secondary differential image (ST4). The output values of the reconstituted differential value image are substituted in an output expression to calculate the output values of the pixels of interest.