Patent ID: 6690490
Filing Date: 2004-02-10
Classification: H04N

Abstract:
An image processor comprising:image inputting means for inputting an image; gradation correction processing means for performing a gradation correcting process using a correction curve to the inputted image; and image outputting means for outputting the image for which the gradation correcting process has been performed, the image inputting means supplying input density values of pixels composing the image, to the gradation correction processing means, the gradation correction processing means supplying correction values on the correction curve to the input density values, to the image outputting means, the image processor further comprising: reference correction curve storing means for storing a reference correction curve indicative of predetermined changes of the correction values to the input density values; and correction amount storing means for storing correction amounts wi and wi+1 which are preset based on the reference correction curve and correspond to a plurality of specified density values XPi and XPi+1, respectively, which are input density values specified at intervals from each other within the range of the input density values, wherein the correction amount wi corresponding to the specified density value XPi is a difference between a correction value YB(XPi) on the reference correction curve to the specified density value XPi and a correction value YP(XPi) to the specified density value on the correction curve, the gradation correction processing means, in order to create the correction curve to be used for the gradation correcting process, (a) calculates the correction values YP(XPi) and YP(XPi+1) to the specified density values XPi and XPi+1 on the correction curve, by adding the correction values to the specified density values XPi and XPi+1 on the reference correction curve and the correction amounts wi and wi+1 corresponding to the specified density values XPi and XPi+1, and (b) calculates the correction value to the input density value other than the specified density value by means of interpolation operation for causing a shape of a part of the correction curve within a first section &Dgr;XPi having the specified density values XPi and XPi+1 as both ends thereof, to coincide with a shape obtained by expanding or compressing in the direction X parallel to the axis of density value, a part of the reference correction curve within a second section &Dgr;YBi having the correction values YP(XPi) and YP(XPi+1) to the specified density values as both ends thereof.