Patent ID: 8300974

Claim:
An image processing device for interpolating a tone in image data, the image processing device comprising: an input unit that inputs the image data; a tone transformation unit that performs a tone transformation of the inputted image data; a threshold-value control unit that sets a threshold value corresponding to a tone; a smoothing filter unit that calculates a tone differences between a given pixel and a pixels near said given pixel in the image data that has undergone tone transformation, and performs a filtering process in such a way that, when the calculated tone difference is larger than the threshold value, then the given pixel is determined to be an edge portion and is not smoothed, and otherwise applies a smoothing process to the given pixel; and an output unit that outputs image data having been processed by the smoothing filter unit, wherein the threshold-value control unit sets the threshold value in such a way that a threshold value for a tone in an area where a tone difference in the image data after the tone transformation becomes larger than that in the image data before the tone transformation is at least as large as a threshold value for a tone in an area where the tone difference in the image data after the tone transformation becomes smaller than that in the image data before the tone transformation.