An image forming apparatus according to an embodiment of the invention
reads an original by mechanically moving an axial light source in a
subscanning direction perpendicular to the axis. The image forming
apparatus includes: a sensor whose resolution in a main scanning
direction parallel to the axis of the axial light source is higher than a
designated resolution; a controller that controls the driving speed of
the axial light source so that the resolution in the subscanning
direction is higher than the designated resolution; an
original-image-data generating unit that generates original image data
with a resolution higher than the designated resolution in response to
the output from the sensor; and an image reducing unit that generates
reduced pixels fewer than a specified number of pixels in the original
image data to generate a reduced image with a resolution equal to the
designated resolution.