JPS647770A - Adjusting method for gradation in preparing printed picture - Google Patents

Abstract

PURPOSE:To obtain an ideal network dot gradation characteristic and to facilitate the management of the generation of a netword dot gradation picture by setting the correlation between an arbitrary sample dot basic density value on an original picture and the network dot area percent of a sample dot on a printed picture corresponding to said sample dot on the original picture so as to satisfy a prescribed relational expression, and processing them. CONSTITUTION:In generating a network dot gradation picture which is a printed picture from a continuous gradation picture which is an original picture, the processing is so achieved that the basic density value of an arbitrary sample dot on the original picture the difference between the density value of the sample dot and that of the brightest dot on said picture and the network dot area percent of a sample dot on the printed picture corresponding to the former sample dot come in the correlation shown by the relational expression. In the expression, assuming the basic density value is as (x), the numerical value of the network dot percent as (y), the network area percent value of a dot in desired arbitrary size set against the brightest part H of the printed picture as (yh), the network dot area percent value of a network dot in an arbitrary size set against a brightness part S as (ys). Also, the reflection ratio of a print paper is assumed as beta, the reflection ratio of print ink as alpha, and the ratio of printed picture density area/original picture density area is assumed as zeta.