Patent ID: 8085437

Claim:
An image forming apparatus, comprising: an expansion unit configured to expand image data input to the image forming apparatus to first matrix data formed of a plurality of rows and columns; a first mask unit configured to mask the first matrix data by performing a logical operation on the first matrix data and on a mask pattern that is second matrix data formed of a plurality of rows and columns, the number of rows and columns of the second matrix data being smaller than a number of rows and columns of the first matrix data; a second mask unit configured to select one of first processing, which completely masks a unit area of the first matrix data corresponding to one of a plurality of mask unit areas of third matrix data, and second processing, which masks the unit area of the first matrix data corresponding to the one of the plurality of mask unit areas of the third matrix data by using the first mask unit, the second mask unit selects one of the first processing and the second processing for each of the plurality of mask unit areas by using the third matrix data, the second matrix data corresponding in size to one of the plurality of mask unit areas of the third matrix data, and each of the plurality of mask unit areas of the third matrix data being formed of the same number of rows and columns as the second matrix data; and an image formation unit configured to form an image by modulating the first matrix data that is masked by the second mask unit into an optical writing signal, wherein the third matrix data, in which one of the first processing and the second processing selected by the second mask unit is assigned to each of the plurality of mask unit areas, is successively moved over an entire area of the first matrix data in units of the third matrix data to mask the first matrix data.