Patent Document ID: 7542053
Application ID: 11093674
Patent Status: 1

Claim One:
1. A method for re-scaling image by variable re-scaling factor, the method comprising: receiving by a re-scaling circuit a sequence of samples that represents a row of pixels in an image; selecting a re-scaling factor for at least a portion of said row of pixels; selecting a filter from a bank of low pass filters in the re-scaling circuit based on the selected re-scaling factor; low-pass filtering the sequence of samples with the selected filter; upsampling the low-pass filtered sequence of samples by a factor M with a polyphase filter bank in the re-scaling circuit having a windowed sinc(t) characteristic, M being a positive integer; and down-sampling with a down-sampling block in the re-scaling circuit the polyphase-filtered sequence of samples by a factor N, N being an integer selected such that M/N is substantially equal to the selected re-scaling factor; wherein the re-scaling factor varies depending on a current position along said row of pixels; wherein said upsampling with the polyphase filter bank includes: implementing the polyphase filter bank with a table that comprises a plurality of rows and a plurality of columns; setting a first variable to equal an inverse of a currently selected scaling factor; initializing a second variable; and at each pixel location in said row of pixels; setting a main tap of the polyphase filter bank at an index indicated by an integer portion of the second variable; setting a third variable to equal a non-integer portion of the second variable; selecting a row from said table in accordance with a value of the third variable; filtering the sequence of samples by a phase of the polyphase filter bank which corresponds to the selected row from said table; and increasing a value of the second variable by a value of the first variable.