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Abstract

An image signal processing apparatus has an address generator that generates addresses for successive words of a digital input signal representing an input image to be manipulated. A computation circuit monitors the addresses for successive word sets which each comprise first and second words relatively horizontally spaced in the input image and a third word aligned vertically with the second word, and computes from each set both horizontal and vertical local scaling factors representing the extent of compression in the horizontal and vertical directions of a corresponding local area of the manipulated image. A bandwidth controller is responsive to the successive scaling factors to vary the horizontal and vertical bandwidths of a digital filter which two-dimensionally filters the input image, thereby to minimize aliasing that would be caused by the manipulation of the local areas. The computation circuit computes the scaling factors for each local area such that the horizontal factor corresponds to the length of a line that extends perpendicularly from a line passing through the positions of the second and third words in the manipulated image to the position of the first word and the vertical factor corresponds to the length of a line that extends perpendicularly from a line passing through the positions of the first and second words to the position of the third word.

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First Claim