An image forming apparatus for forming an image, comprising: storage means configured to store at least a plurality of lines of image data; and data reading means configured to read image data in a line direction from said storage means based on a read start address, characterized in that the image forming apparatus further comprises: setting means configured to set line switching address in the line direction, for switching a line of the image data to be read by said data reading means from a first line to a second line; generating means configured to generate the read start address of the second line in a case where said data reading means switches the line of the image data from the first line to the second line, so that the read address of the first line in the line direction overlaps the read address of the second line in the line direction; control means configured to control said data reading means to read image data of the second line based on the read start address generated by said generating means in a case where the read address, in the line direction, and to read the image data of the first line become identical to the line switching address; halftone processing means configured to perform halftone processing based on the image data of the first line and the image data of the second line read by said data reading means; and image forming means configured to form an image based on the image data to which the halftone processing is performed by said halftone processing means. storage means configured to store at least a plurality of lines of image data; and data reading means configured to read image data in a line direction from said storage means based on a read start address, characterized in that the image forming apparatus further comprises: setting means configured to set line switching address in the line direction, for switching a line of the image data to be read by said data reading means from a first line to a second line; generating means configured to generate the read start address of the second line in a case where said data reading means switches the line of the image data from the first line to the second line, so that the read address of the first line in the line direction overlaps the read address of the second line in the line direction; control means configured to control said data reading means to read image data of the second line based on the read start address generated by said generating means in a case where the read address, in the line direction, and to read the image data of the first line become identical to the line switching address; halftone processing means configured to perform halftone processing based on the image data of the first line and the image data of the second line read by said data reading means; and image forming means configured to form an image based on the image data to which the halftone processing is performed by said halftone processing means. setting means configured to set line switching address in the line direction, for switching a line of the image data to be read by said data reading means from a first line to a second line; generating means configured to generate the read start address of the second line in a case where said data reading means switches the line of the image data from the first line to the second line, so that the read address of the first line in the line direction overlaps the read address of the second line in the line direction; control means configured to control said data reading means to read image data of the second line based on the read start address generated by said generating means in a case where the read address, in the line direction, and to read the image data of the first line become identical to the line switching address; halftone processing means configured to perform halftone processing based on the image data of the first line and the image data of the second line read by said data reading means; and image forming means configured to form an image based on the image data to which the halftone processing is performed by said halftone processing means.