Abstract: A plate-making method for manufacturing a printing plate includes: manufacturing the printing plate based on a knockout method in which knockouts of halftone dots in one color are formed, and halftone dots in the other color are overprinted onto positions of the knockouts; for each of pixels, when a sum of a halftone dot area ratio of the one color and a halftone dot area ratio of the other color is smaller than 100%, forming a gap from a knockout in the one color around a halftone dot in the other color; and for each of pixels, when the sum of the halftone dot area ratio of the one color and the halftone dot area ratio of the other color is greater than 100%, forming an overmask such that the halftone dot in the other color penetrates a periphery of the halftone dot in the one color.

Abstract: There is provided a plate-making method for manufacturing printing plates capable of representing colors by overprinting halftone dots in at least three colors of a plurality of process colors. The plate-making method includes: overprinting two colors of the at least three colors by a knockout method in which knockouts of halftone dots in one color of the two colors are formed, and halftone dots in the other color are overprinted onto positions of the knockouts; and overprinting a remaining color of the at least three colors onto the two colors by an overprint method in which at least part of halftone dots in the remaining color is put on the halftone dots in the one color and/or the halftone dots in the other color. The remaining color includes at least white.

Abstract: A plate-making method for manufacturing a printing plate includes: manufacturing the printing plate based on a knockout method in which knockouts of halftone dots in one color are formed, and halftone dots in the other color are overprinted onto positions of the knockouts; for each of pixels, when a sum of a halftone dot area ratio of the one color and a halftone dot area ratio of the other color is smaller than 100%, forming a gap from a knockout in the one color around a halftone dot in the other color; and for each of pixels, when the sum of the halftone dot area ratio of the one color and the halftone dot area ratio of the other color is greater than 100%, forming an overmask such that the halftone dot in the other color penetrates a periphery of the halftone dot in the one color.