1. An image quality adjusting mechanism comprising: storage means for storing a plurality of predetermined input-output image density characteristics; selecting means for selecting at least one of the plurality of predetermined input-output image density characteristics; and sharpness changing means for changing a sharpness of an image; wherein said sharpness changing means changes the sharpness of the image based on a selected input-output image density characteristic so that the sharpness of the image is decreased as the selected input-output image density characteristic becomes more linear.