PURPOSE: To edit a photographic image and a character illustration in a free layout to immediately output them by forming an image wherein gradation is expressed by setting the number of dots and density of one pixel constituted of a plurality of dots on a transparent support using a heat-diffusible dye.

CONSTITUTION: An image wherein gradation is expressed by setting the number of dots and density of one pixel constituted of a pluraity of dots is formed on a transparent support using a heat-diffusible dye. That is, not only an image of gradation expression (density gradation) due to a density change but also an image of gradation expression (area gradation) due to a density and area change are formed. An image editing part 31 performs editing in two layers and the image data of the first layer is made preferential to be converted to the data for the output of a printer 3 by a density gradation converting table. The image data of the second layer is converted in the same way by an area gradation converting table. As a result, irregularity is eliminated and gradation expression is also improved.