Abstract: Apparatus with optical detecting device for reading a mark sheet provided with plural mark rows, each of which includes a reference mark, a skew detection mark and mark writing regions. The apparatus reads the mark sheet by use of a predetermined nominal scan window address for each of the regions. Optical shift of the optical detecting device is detected and the scan window addresses are corrected in accordance with the detected shift. Further, skew of the mark sheet is detected, and scan lines for reading the mark sheet is selected in accordance with the detected skew.

Abstract: An image scaling method and apparatus partitions each line of image pel (print element) indicating bits into a number of bit groups equal to the number of bits to be added or deleted from the line to achieve a desired scaling. In each of the bit groups, one pel is added for enlargement or one pel is deleted for reduction. The pel addition or deletion occurs at pairs of like-pel indicating bits. If any bit groups has no pairs of like-pel indicating bits, a pel indicating bit is added for enlargement or deleting for reduction in an arbitrary location in the bit group.