An image signal processing apparatus may include a line sensor for photoelectrically reading an original image and outputting an image signal, a rotary encoder for setting reproduction magnifications of the original image, an edge emphasis circuit for performing edge emphasis processing for the image signal output from the line sensor, and W- and R-address counters and first and second clock cotnrol signals, all of which cooperate to control a degree of edge emphasis performed by the edge emphasis circuit in accordance with the reproduction magnification set by the rotary encoder. The magnification can preferably be set independently for the main scanning and the sub-scanning directions. A correction signal is used in the edge emphasis processing, and is preferably formed on the basis of image signals of pixels near the particular pixel of interest. The image signal may also be smoothed after edge emphasis.