Digital printer and image data conversion method

摘要

In a digital printer, a great number of images recorded on the same type recording medium as an original to be reproduced are roughly pre-scanned prior to main scanning of the original. The pre-scanning image data is sorted according to green density levels, and red and blue densities of those pixels which are selected according to a standard are respectively accumulated for each green density level. Mean values of the red and blue densities accumulated in the respective green density levels are used as the pixel selection standard. Different kinds of gradation balance data are obtained by use of different methods from the mean values of the accumulated image data and/or image data of the original, to derive optimum gradation balance data from these different kinds of gradation balance data by selecting and combining the data. A gradation conversion table is produced from the optimum gradation balance data and previously stored gradation curve data. Main scanning image data of the original is converted through the gradation conversion table.