Printing image data generating device, thermal transfer printer, and computer program

A thermal transfer printer comprising:

• a thermal head that extends in a scanning direction and thermally transfers ink of a ribbon onto paper on a line-by-line basis, the thermal head pressing the ribbon onto the paper conveyed with the ribbon along a sub scanning direction perpendicular to the scanning direction;
• an image data acquirer configured to acquire input image data as a printing subject, the input image data being for plural lines each having plural pixels;
• a density deviation line specifying section configured to specify, of the plural lines, density deviation lines predicted to exhibit a deviation in printing density from a predetermined printing density due to a change in friction force between the thermal head and the ribbon at the density deviation lines, the change in the friction force being based on grayscale values of the pixels included in the plural lines;
• a correction-subject pixel specifying section configured to specify any particular pixel in the density deviation lines as a correction-subject pixel when a variation degree of the grayscale value between the correction-subject pixel and other pixels in a predetermined evaluation area is lower than a first predetermined value, the predetermined evaluation area including at least the particular pixel and two pixels adjacent to the particular pixel in the sub scanning direction;
• a correcting section configured to correct the grayscale value of the correction-subject pixel and to generate a corrected grayscale value such that the deviation of the printing density at the correction-subject pixel is reduced;
• and
• a generating section configured to generate the printing image data based on the input image data and the corrected grayscale value generated by the correcting section.

A non-transitory computer-readable medium having instructions recorded thereon that perform a method when executed by a computer, the computer generating printing image data used for a thermal transfer printer having a thermal head that extends in a scanning direction and thermally transfers ink of a ribbon onto paper on a line-by-line basis, and the thermal head pressing the ribbon onto the paper conveyed with the ribbon along a sub scanning direction perpendicular to the scanning direction, the method comprising:

• acquiring input image data as a printing subject, the input image data having plural lines each having plural pixels;
• specifying density deviation lines of the plural lines including predicting which density deviation lines exhibit a deviation in printing density from a predetermined printing density due to a change in friction force between the thermal head and the ribbon at the density deviation lines, the change in the friction force being based on grayscale values of the pixels included in the plural lines;
• specifying any particular pixel in the density deviation lines as a correction-subject pixel when a variation degree of the grayscale value between the correction-subject pixel and other pixels in a predetermined evaluation area is lower than a first predetermined value, the predetermined evaluation area including at least the particular pixel and two pixels adjacent to the particular pixel in the sub scanning direction;
• correcting the grayscale value of the specified correction-subject pixel, and generating a corrected grayscale value such that the deviation of the printing density at the correction-subject pixel is reduced;
• and
• generating the printing image data based on the input image data and the corrected grayscale value.