Patent ID: 6486888
Filing Date: 2002-11-26
Classification: G06T

Abstract:
A method for storing and processing arbitrary 2-dimensional shapes in a graphics system, comprising:creating an alpha image data structure from an image data source, wherein the alpha image data structure comprises the following elements: data representing the starting location and extent of a span of pixels of a scanned image of a shape, wherein the span of pixels is semi-transparent; data representing the alpha values quantifying the opacity of each pixel of the semi-transparent span; combining the alpha image data structure with a second alpha image data structure, wherein the second alpha image data structure represents a second image data source; storing the combined alpha image data structures in a third alpha image data structure; and rendering the third alpha image data structure onto a drawing surface; wherein creating an alpha image data structure from an image data source further comprises: recording the number of adjacent spans having an identical pattern of alpha values that comprise the arbitrary 2-dimensional shape in the alpha image data structure; classifying each span or portion of a span as semi-transparent or opaque, and storing the starting location and extent of each span or portion of a span in the alpha image data structure, wherein the extent is stored as a positive number if the span or portion of a span is opaque, and is stored as a negative number if the span or portion of a span is semi-transparent; recording the alpha values associated with the semi-transparent spans or portions of spans, in the alpha image data structure, wherein only the first occurrence of an identical pattern of alpha values occurring within the arbitrary 2-dimensional shape is recorded; recording the location of the semi-transparent or opaque spans and portions of spans in a first offset of the alpha image data structure; recording the location of the alpha data for the adjacent span having an identical pattern of alpha values in a second offset of the alpha image data structure.