| 摘要 |
PROBLEM TO BE SOLVED: To enable improvement of the visual quality of an image after gradation conversion. SOLUTION: In a gradation modulator 200 serving asΔΣmodulator for converting the gradation of an image, an adder 250 adds a pixel value of the image and the output of a feedback computing section 240, a quantizing section 210 quantizes the output of the adder 250 and outputs a quantized value including a quantization error as the result of theΔΣmodulation. A subtracter 230 then calculates the difference between the output of the adder 250 and the quantized value of the output of the adder 250 to determine the quantization error, and a feedback computing section 240 filters the quantization error and outputs the result of the filtering to the adder 250. The filter coefficient of the filtering by the feedback computing section 240 is so determined that the characteristics in the intermediate or higher band of the amplitude characteristic of noise shaping by theΔΣmodulator may be the inverse of the spatial frequency characteristic of the visual sensation of the human. The invention can be applied to image gradation conversion. COPYRIGHT: (C)2009,JPO&INPIT |
