Image resizing system and method
Image resizing through resampling by poly-phase filtering with a phase generation from input parameters but with lower resolution of the phase for filter selection. Field and frame mode selection creates initial offsets for alignment. A phase accumulator generates sample addressing with its most significant bits, generates filter selection with its middle bits, and maintains its least significant bits for accuracy.
1. A method of sampling rate conversion which uses poly-phase filtering, the improvement comprising:
(a) generating a phase with a first resolution; and
(b) selecting poly-phase filters using said phase at a second resolution which is coarser than said first resolution.
2. A method of image resampling which uses horizontal and vertical poly-phase filtering, the improvement comprising:
(a) generating a phase at a first resolution using input parameters;
(b) selecting poly-phase filters from said phase for horizontal filtering to output resampled lines, said selecting uses said phase at a second resolution which is coarser than said first resolution, and
(c) selecting poly-phase filters from said phase for vertical filtering of the resampled lines from step (b) to output a resampled image, said selecting uses said phase at a second resolution which is coarser than said first resolution.
3. The method of claim 2 wherein:
(a) the image is in a video sequence with interlaced fields or progressive frames; and
(b) the vertical resampling adjusts among top field, bottom field, and frame by initial phase offsets.
4. An image resampler, comprising:
(a) a phase generator;
(b) a filter coefficient memory with address input coupled to a truncated output of said phase generator, said truncated output discarding the least significant bits of a phase generated by phase generator; and
(c) a filter with an image input and filter coefficients stored in said memory.
5. The resampler of claim 4 , wherein:
(a) said phase generator and said filter are implemented as programs on a programmable processor.