1. An image forming apparatus to improve image quality, the image forming apparatus comprising: an edge detecting unit to detect an edge pixel from image data; an edge processing unit to determine whether the edge pixel is a color edge pixel or a black edge pixel by using a chrominance component of the edge pixel, the edge processing unit comprising: a color edge adjusting unit to apply a first edge sharpening method to the edge pixel if the edge pixel is the color edge pixel, the first edge sharpening method including determining an area of the image data where the color edge pixel is located and adjusting a luminance value of the color edge pixel with reference to luminance values of pixels adjacent to the color edge pixel in the determined area; and a black edge adjusting unit to apply a second edge sharpening method to the edge pixel if the edge pixel is the black edge pixel such that the first edge sharpening method and the second edge sharpening method are different; and a print unit to print the image data using the processed edge pixel.