<p>A plurality of closed areas (HA) constituting a line drawing image are extracted to display them on a display means (12) and a desired closed area out of the displayed closed areas is specified by an operating means (13) to extract it as an image layer (GL). At this time, a closed area display screen (HG) for displaying the extracted closed areas and an image layer display screen (GG) for displaying the extracted image layer are displayed on the display means in parallel, thereby making it possible to easily discriminate whether or not a proper closed area has been converted into an image layer. Further, if a plurality of closed areas are specified, the specified closed areas are extracted as the image layers and the closed areas can be treated collectively as one image layer. This produces an action effect that both efficiency of line drawing painting by image layer processing and efficiency of line drawing painting by closed area extraction are achieved.</p>
