| 摘要 |
PURPOSE: To display an image in an optimum state by taking a frequency characteristic of human eyes into account and applying positive feedback spread processing to a quantization error of an image signal to reduce relative noise at low frequencies. CONSTITUTION: When a quantization error in a base pixel 4 is +1, and +1, -1, -1 are respectively added to analog data of three pixels 13, 14, 16 adjacent to the base pixel before quantization of the three pixels 13, 14, 16 and a quantization error is spread with respect to all pixels according to the relation above. A same value and a same sign as those of the obtained error are added to pixels resident in diagonal lines with respect to the base pixel and a same value but an opposite sign as those of the obtained error are added to pixels resident in right and downward directions in this way, then noise strength in horizontal and vertical directions is zero and the noise strength in the diagonal directions approaches zero at low frequencies along a quadratic curve and increases at high frequencies, but the visual characteristic of human eyes is not sensitive to noise at high frequencies and in diagonal directions. |
