system and method for shaking and the quantization of image data to optimize the visual quality of the recovered image

摘要

A color graphics pipeline (11) has a separate encoder (14r, 14g, 14d) with a dither table (33r, 33g, 33b) for processing each color value (34r, 34g, 34b) in pixel data (33) received from a host processor (12) or rasterizer. The encoders (14r, 14g, 14b) modify color values (34r, 34g, 34b) and dither noise values and also combine both positive and negative dither noise values with the color values (34r, 34g, 34b), for independent optimization of each color and for better edge detection in a color recovery filter within a decoder (18) of the pipeline (11). Each encoder (14) comprises the following elements. A comparator mechanism (48) compares a color value (34) with a predetermined cutoff value. A dither table (33) provides dither noise values (37). An offset mechanism (56) modifies the dither noise values (37) to derive a modified dither noise value (63) when the color value (34) is greater than or equal to the predetermined cutoff value. An aliasing mechanism (43) aliases the color value (34) with other color values (34) below the predetermined cutoff value to derive an aliased color value (47) when the color value (34) is less than the predetermined cutoff value. An adder mechanism (38) adds the unmodified dither noise (63) or modified dither noise (63) to the aliased color value (53) or nonaliased color value, respectively, to derive the dithered color value (64). A clamping mechanism (66) ensures that the dithered color value (64) resides within a predetermined color range. Finally, a quantizing mechanism (42) quantizes the dithered color value (74) to derive a quantized/dithered color value (43) for storage in memory, such as in a frame buffer (16). IMAGE