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Abstract

A dynamically variable anti-aliasing filtering system calculates on a local basis the compression factors (Cf) present in an image that is being mapped from a two-dimensional source image through a three-dimensional space and into a two-dimensional target image, the apparatus implementing a linear equation of the form: Cf=A*X.sub.s +B*Y.sub.s +C where, X.sub.s and Y.sub.s are, respectively, the horizontal and vertical coordinates of pixels in the source image, and A, B and C are precalculated (each field or frame) constants that depend on the transform matrix function F. A total of four compression factors are required, one for control of horizontal luminance filtering, one for control of vertical luminance filtering, one for control of horizontal chrominance filtering and one for control of vertical chrominance filtering. Three dual accumulator circuits are used to implement the linear equation in X.sub.s and Y.sub.s for three different sets of A, B and C. One of these circuits measures horizontal chrominance compression, one vertical luminance compression and one compression due to skew angles. The outputs of these circuits are converted to logarithms and combined with each other and with the logarithms of multiplicative constants representing the ratios between calculated compression factors and the other required compression factor to produce those other compression factors.

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