JPS5775061A - Variable magnification method for harf tone picture - Google Patents

Abstract

PURPOSE:To reduce the occurrence of moire, by dispersing the density of each picture element after variable magnification to picture elements around this picture element in case of the variable magnification processing to give a regularity to the picture signal after the variable magnification processing as less as possible. CONSTITUTION:Respective picture elements of a coming scanning picture signal are stored in a buffer memory 2. Addresses of picture elements before variable magnification which overlap one another for addresses of picture elements after variable magnification are designated by an extracting counter 4, and their densities are given to a variable magnification density memory 5, and addresses of picture elements before variable magnification adjacent or near said addresses of picture elements before variable magnification are designated, and their densities are given to an adding circuit 6. The variable magnification density memory 5 gives a density output after variable magnification, which is calculated in accordance with the area ratio of addresses of picture elements before variable magnification, to a comparator 7, and this density output is compared with the threshold of a thershold level memory 8 to transmit a variable magnification output signal. Simultaneously, a differential output obtained from a differentiator 9 is accordance with the variable magnification output signal is inputted to the adding circuit 6 through weighting coefficient equipment 10, and thus, a new density is stored in the buffer memory 2.