| 摘要 |
<p>Apparatus for processing a first signal representing a colour component of a pixel of an image in which the signal defines the value of the colour component as one of a first set of values defining a first scale of colour component values. The apparatus comprises a first Look-up Table (LUT) (2) addressed by the colour component value for generating a second signal representing a modified colour component value chosen from a set of modified colour component values defining a second scale coarser than the first scale. An adjustment circuit (3; 7-9) comprises a memory (3,9) in which at least two sets of adjustment data are stored, each set being associated with a respective dither threshold representing respective differences, hereinafter referred to as quantisation errors, between the first and second signals when compared on the first scale of colour component values, the data of each set defining an adjustment instruction for each possible quantisation error, the adjustment instruction being related to the difference between the quantisation error and the respective dither threshold. The adjustment circuit means receives the first signal so that the memory is addressed by a signal related to the quantisation error and related to the position of the pixel in the image so as to generate an adjustment control signal associated with the quantisation error and the dither threshold corresponding to the first signal pixel. A modifying circuit (5) is responsive to the adjustment control signal generated by the adjustment circuit to adjust the second signal to generate a final output signal representing one of the second set of the colour component values.</p> |
