Patent Document ID: 5465118
Application ID: 08170044
Patent Status: 1

Claim One:
1. An image processing system which compresses a digitized video image comprising: A. means for partitioning the image into non-overlapping contiguous regions containing a plurality of pixels each having a unique luminance value indicative of the luminance of its associated pixel; and B. means for compressing the luminance information of pixels in each region by encoding the luminance values within each region into a compressed code, wherein said means for compressing includes: 1. means for comparing the luminance values of the pixels located along the perimeter of a region to determine a pixel containing the smallest luminance value and its location within the region and for providing a base luminance value indicative of the smallest luminance value; 2. means for determining direction of greatest luminance change from the base luminance value location; 3. means for computing a total change in luminance along the direction of greatest luminance change starting from the base luminance value location; 4. means for selecting a transition function value indicative of the type of luminance transition within the region starting from the location of the base luminance value wherein the luminance transition values are indicative of the following functions: a. a linear luminance transition; b. a low contrast luminance edge transition at one quarter of the distance across the region; c. a low contrast luminance edge transition at one half of the distance across the region; d. a low contrast luminance edge transition at three quarters of the distance across the region; e. a high contrast luminance edge transition at one quarter of the distance across the region; f. a high contrast luminance edge transition at one half of the distance across the region; and g. a high contrast luminance edge transition at three quarters of the distance across the region; and 5. means for generating a digitized encoded data stream containing encoded data indicative of the direction of greatest luminance change and an index value representative of the luminance characteristics within the region, wherein the index value is selected as a function of the base luminance value, the direction of greatest luminance change, the total change in luminance value, and the transition function value wherein said means for generating a digitized encoded data stream, further comprises: means for generating a short code of compressed video image data comprising i) M.sub.1 number of bits indicative of the direction of greatest luminance change, and ii) M.sub.2 number of bits indicative of the base luminance value; means for generating a medium length code of compressed video image data comprising i) M.sub.3 number of bits indicative of the direction of greatest luminance change, ii) M.sub.4 number of bits indicative of an index value which is a pointer to an array containing encoded luminance information; and means for providing said encoded data stream as said short length code when the value of total variation in luminance is less than a first threshold value, and for providing said encoded data stream as said medium length code when the value of the total variation in luminance is not less then the first threshold value.