A computer-implemented method of generating a dither matrix in which halftone dots are formed by growing corresponding dots, the method comprising: a first generating step of generating first threshold values of a dither matrix, so that the dots are grown until a predetermined halftone dot area ratio is achieved, wherein, when the predetermined halftone dot area ratio is achieved, the halftone dots contact each other; and a second generating step of generating second threshold values of the dither matrix, so that the dots grow beyond the predetermined halftone dot area ratio wherein the first generating step includes a first process of growing the dots by using a concentration type dither matrix, recording centroid positions of the corresponding halftone dots at a moment at which the halftone dots contact each other and blank dot positions at which dots do not grow, and assigning threshold values to the corresponding centroid positions of the halftone dots in an ascending order from a smallest value among the threshold values; a second process of assigning, in an ascending order, threshold values greater than the threshold values of the first process to positions at which corresponding isolated dots are to be generated, wherein the positions are included in candidate positions, the candidate positions being defined to be positions farthest from the corresponding centroid positions, except for the blank dot positions; a third process of assigning threshold values greater than the threshold values of the second process in an ascending order to remaining candidate positions; and a fourth process of assigning threshold values greater than the threshold values of the third process in an ascending order to positions within outline positions of the corresponding halftone dots. a first generating step of generating first threshold values of a dither matrix, so that the dots are grown until a predetermined halftone dot area ratio is achieved, wherein, when the predetermined halftone dot area ratio is achieved, the halftone dots contact each other; and a second generating step of generating second threshold values of the dither matrix, so that the dots grow beyond the predetermined halftone dot area ratio wherein the first generating step includes a first process of growing the dots by using a concentration type dither matrix, recording centroid positions of the corresponding halftone dots at a moment at which the halftone dots contact each other and blank dot positions at which dots do not grow, and assigning threshold values to the corresponding centroid positions of the halftone dots in an ascending order from a smallest value among the threshold values; a second process of assigning, in an ascending order, threshold values greater than the threshold values of the first process to positions at which corresponding isolated dots are to be generated, wherein the positions are included in candidate positions, the candidate positions being defined to be positions farthest from the corresponding centroid positions, except for the blank dot positions; a third process of assigning threshold values greater than the threshold values of the second process in an ascending order to remaining candidate positions; and a fourth process of assigning threshold values greater than the threshold values of the third process in an ascending order to positions within outline positions of the corresponding halftone dots.