1. An image processing device comprising: a first area extracting computer processor unit configured to extract at least a first document area from document image data by dividing the document image data in units of a document area; a language determining computer processor unit configured to determine a type of a language used in the document image data; and a second area extracting computer processor unit configured to extract a second document area by dividing the first document area based on a rule corresponding to the type of the language determined by the language determining unit, and also configured to extract the second document area by combining the first document area with at least another different unit of a document area based on a rule corresponding to the type of the language determined by the language determining unit, wherein the first area extracting computer processor unit includes a white-block extracting computer processor unit configured to extract, from a document area unit of binary document image data, a maximum white-block group by identifying a preliminary group of at least one white-block according to an evaluation function, estimating a font size based on a distribution of black blocks in document area units, and eliminating white-blocks from the preliminary group according to the estimated font size, and a white-block dividing computer processor unit configured to divide the document area unit into a plurality of document area units by using the at least one white-block in the maximum white-block group extracted by the white-block extracting unit as separators, wherein the white-block extracting computer processor unit is configured to extract the plurality of document area units divided from the document area unit and place them in a stack, and is further configured to extract another maximum white-block group from a document area unit at a top of the stack, and wherein the first area extracting computer processor unit is configured to extract the maximum white-block group, divide the document area unit, and extract the plurality of document area units until the stack is empty.