Patent US 4,885,786

The method according to the present invention enlarges a binary digital image by a method comprising the steps of: storing the rows of the image as a plurality of run end representations, in which a row is represented as a sequence of values giving the white and black run ends; enlarging each row of the image along the horizontal axis by altering the value of each run end representation to achieve enlargement on the horizontal axis by a factor F1; enlarging the image along the vertical axis by interpolating rows between the lines of the partially enlarged image so as to produce enlargement along the vertical axis by a factor F2; storing the enlarged size image generated by the above steps in run end form. An image enlarged by the method of the present invention may be reduced by the simple technique of dividing the image into blocks of pixels and assigning one pixel in a reduced image for each block of pixels in the larger image. Each pixel in the reduced image may by set equal to a center pixel in each block.