Abstract: PROBLEM TO BE SOLVED: To ensure matching of a single scanning digital input device with a gradation range with a dynamic range while compensating a change in a sensor response or the like due to the effect of heat during low speed scanning.

SOLUTION: Histograms of incidence of each gradation level are collected during scanning (210) and a color of a background of an image (gradation of paper) is estimated (250) by analyzing the histogram (230). Thus, exposure is controlled independently of gradation reproduction. This process is repeated sometimes during scanning to ensure the result thereby compensating a drift of the sensitivity of the sensor (290).

Int'l Class: H04N00104; G06T00100; H04N00140

Priority: US 96 724711 19960930