A display processing apparatus that performs display processing of a preview image showing a result of image formation of document data in an image forming apparatus, the document data including color plane image data and transparent plane image data, the color plane image data including a plurality of drawing areas and indicating an area for which use of a color developer in the image forming apparatus is specified, the transparent plane image data indicating an area for which use of a transparent developer in the image forming apparatus is specified together with a type of transparent processing performed on the area by using the transparent developer on the respective drawing areas with the respective type of transparent processing, the display processing apparatus comprising: a preview image processing unit configured to generate transparent display planes equal in number to the number of types of transparent processing specified in the document data, wherein the drawing areas having the same type of transparent processing (311, 321) are indicated in the same transparent display plane, and to generate a preview image including all the generated transparent display planes, said preview image processing unit including: a transparent display data generating unit that generates, based on the document data, a plurality of pieces of transparent display data (310, 320) that show a result of image formation corresponding to the transparent processing performed with the transparent developer on the drawing areas on which the same transparent processing is performed for each type of the transparent processing; and a preview image generating unit that arranges a color display plane on which the color plane image data is displayed at a predetermined position of the color display plane in the preview image and arranges in a superimposed manner a plurality of transparent display planes on which the pieces of transparent display data (310, 320) are displayed at a plurality of positions of the transparent display planes that are determined based on the position of the color display plane in accordance with a predetermined rule and that are different from one another, so as to generate the preview image obtained by projecting the color display plane and the transparent display planes that are arranged in a three-dimensional space onto a two-dimensional plane; and a display control unit that displays the preview image on a display screen. a preview image processing unit configured to generate transparent display planes equal in number to the number of types of transparent processing specified in the document data, wherein the drawing areas having the same type of transparent processing (311, 321) are indicated in the same transparent display plane, and to generate a preview image including all the generated transparent display planes, said preview image processing unit including: a transparent display data generating unit that generates, based on the document data, a plurality of pieces of transparent display data (310, 320) that show a result of image formation corresponding to the transparent processing performed with the transparent developer on the drawing areas on which the same transparent processing is performed for each type of the transparent processing; and a preview image generating unit that arranges a color display plane on which the color plane image data is displayed at a predetermined position of the color display plane in the preview image and arranges in a superimposed manner a plurality of transparent display planes on which the pieces of transparent display data (310, 320) are displayed at a plurality of positions of the transparent display planes that are determined based on the position of the color display plane in accordance with a predetermined rule and that are different from one another, so as to generate the preview image obtained by projecting the color display plane and the transparent display planes that are arranged in a three-dimensional space onto a two-dimensional plane; and a transparent display data generating unit that generates, based on the document data, a plurality of pieces of transparent display data (310, 320) that show a result of image formation corresponding to the transparent processing performed with the transparent developer on the drawing areas on which the same transparent processing is performed for each type of the transparent processing; and a preview image generating unit that arranges a color display plane on which the color plane image data is displayed at a predetermined position of the color display plane in the preview image and arranges in a superimposed manner a plurality of transparent display planes on which the pieces of transparent display data (310, 320) are displayed at a plurality of positions of the transparent display planes that are determined based on the position of the color display plane in accordance with a predetermined rule and that are different from one another, so as to generate the preview image obtained by projecting the color display plane and the transparent display planes that are arranged in a three-dimensional space onto a two-dimensional plane; and a display control unit that displays the preview image on a display screen.