Patent ID: 6133902
Filing Date: 2000-10-17
Classification: G09G,H04N

Abstract:
A gray scale level reduction method for producing an output image with a reduced number of gray levels, the gray scale reduction method comprising:quantization error scattering input gray level data of an input image including a plurality of pixels, wherein the quantization error scattering includes obtaining temporary quantization gray level data and quantization error data for each pixel of the input image, whereinobtaining the temporary quantization gray level data includes error scattering the input gray level data to produce error scattered gray level data and temporarily quantizing the error scattered gray level data to produce the temporary quantization gray level data, andobtaining the quantization error data includes computing a difference between the temporary quantization gray level data and the input gray level data;storing the temporary quantization gray level data and the quantization error data;regenerating gray level data from the temporary quantization gray level data and the quantization error data and outputting regenerated gray level data as gray level data for each pixel;filtering data produced by the quantization error scattering, after completing the quantization error scattering, including filtering the regenerated gray level data for each pixel and outputting filtered data as modified gray level data; andquantizing the modified gray level data, and outputting quantized gray level data having a smaller number of gray levels than the input image.