1. An image processing apparatus comprising: an original image data memorizing part for storing original image data; a reading part for reading and outputting the original image data at least one line-by-line in a top-to-bottom direction; an image processing part for, upon input of the at least one line, adding ring pixels corresponding to image processing for each input line, performing the image processing, and outputting the image-processed line; an image resizing part for, upon input of the image-processed line, performing enlargement or copy with respect to the image-processed line; and outputting the enlarged or copied line; and an output timing control part for controlling timing for outputting the line from the reading part or outputting the image-processed line from the image processing part wherein the output timing control part determines the timing by using the number of input lines dividing the original image data, the number of output lines output from the at least one filter, and the number of lower ring lines of ring pixels in the respective at least one filters.