Alias avoidance in image processing

Abstract

Image processing apparatus in which output pixel values are generated with respect to pixels of an input image selected in accordance with an image feature direction in the input image comprises means for comparing blocks of pixels of the input image, the blocks being disposed with respect to a pixel position under test so that a correlation between the blocks would indicate an image feature direction applicable to that pixel position; and means for detecting the image feature direction applicable to the pixel position under test as a direction corresponding to a block comparison for blocks having the highest correlation amongst blocks having block contents meeting one or more predetermined criteria.

Description

technical field [0001] The present invention relates to aliasing avoidance in image processing. Background technique [0002] Video image capture represents a spatial and temporal sampling process. Images are captured as a set of pixels arranged in rows or lines. Successive images are captured at spaced apart time instants. [0003] One complication is the common use for interlaced video capture and processing. In an interlaced video signal, each image is manipulated as two sets of alternating pixel lines, or two fields of alternating pixel lines. For example, odd-numbered lines may be included in one field, while even-numbered lines may be included in the next field. One advantage of the interlacing technique is that it gives an apparent doubling of the picture rate, thereby mitigating flicker effects without significantly increasing the video signal bandwidth. [0004] All of the above aspects of sampling can produce aliasing effects if one attempts to capture or proc...

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