An image encoding device equipped with a transformation component which transforms
given image data into transformation coefficients by subjecting this image data
to a frequency decomposition, a dividing component which divides the transformation
coefficients produced by the transformation component into a selected region on
the image and a non-selected region other than the selected region, and an encoding
component which encodes the transformation coefficients by preferentially allocating
a greater quantity of information to the selected region than to the non-selected
region, and the dividing component performs an equation evaluation of numerical
equation data that stipulates the boundary of the selected region, and determines
whether the transformation coefficients belong to the selected region on the basis
of the results of this equation evaluation, to perform the division into a selected
region and non-selected region during image encoding with less processing.
