Image processing apparatus

An image processing apparatus comprising:

• a smoother generating a smoothed signal by smoothing an input image signal, the input image signal generated by combining a plurality of image signals with different bit precisions;
• a bit extender extending a bit width of the input image signal;
• a subtractor performing a subtraction process between the input image signal whose bits are extended by the bit extender and the smoothed signal in order to generate a differential signal;
• a non-linear filter performing a nonlinear process on a pixel value of the differential signal;
• and
• an adder adding one of two signals on which the subtraction process was performed and the differential signal on which the nonlinear process was performed in order to generate an output image signal,
• wherein the nonlinear filter changes its filter characteristic based on a pre-synthesis bit precision of a process target pixel included in the input image signal when the nonlinear process is performed on the pixel value of the differential signal corresponding to the process target pixel.

A method for receiving an input image signal generated by combining a plurality of image signals with different precisions and generating an output image signal obtained by increasing the number of gradation steps of the input image signal by bit extension, the method comprising:

• generating an intermediate signal used to correct the input image signal such a manner that a pixel value corresponding to a halftone increased by the bit extension is included in the output image signal;
• and
• applying a nonlinear filtering to a pixel value of the intermediate signal corresponding to a pixel that is to be processed and included in the input image signal,
• wherein a characteristic of the nonlinear filtering is determined according to a pre-synthesis bit precision of the pixel to be processed.