Patent ID: 6741368
Filing Date: 2004-05-25
Classification: H04N

Abstract:
A method of compressing a two-dimensional image represented as a raster of pixels, each pixel having a value, the method comprising:receiving a sequence of the pixels in raster order; defining a first match pixel location and a second match pixel location relative to a current pixel location in the raster, a first match pixel being the pixel at the first match pixel location relative to the current pixel, a second match pixel being the pixel at the second match pixel location relative to the current pixel, where the first pixel location and the second pixel location are not contiguous in the sequence; considering each pixel in turn as the current pixel, performing the actions of: comparing the current pixel only to the first match pixel and the second match pixel and then encoding the value of the current pixel if the value of the current pixel does not match the value of the first match pixel or the value of the second match; and otherwise if the value of the current pixel matches the value of the first match pixel then encoding the current pixel as a first token where the first token includes a reference to the first match pixel and a length and where the length is determined based on a number of consecutive pixels relative to the current pixel whose values match the values of similarly located pixels relative to the first match pixel; or if the value of the current pixel matches the value of the second match pixel then encoding the current pixel as a second token where the second token includes a reference to the second match pixel and a length and where the length is determined based on a number of consecutive pixels relative to the current pixel whose values match the values of similarly located pixels relative to the second match pixel.