Digital picture scaling

1. A method for scaling a digital picture comprising the following steps:

(a) inputting a source picture to a source memory;

(b) providing a first buffer and a second buffer;

(c) determining scaling factors;

(d) generating initial data in the first buffer and second buffer;

(e) transferring a portion of data of the digital picture from the source memory to the first buffer, the portion of data having a size in a second direction of L and size in a first direction equal to a corresponding size of the source picture;

(f) using an L-tap filter to scale the data in the first buffer in the first direction and storing the scaled data in the second buffer;

(g) using the L-tap filter to scale the data in the second buffer in the second direction and storing the scaled data in a destination memory, the scaled data having a size in the first direction of 2*L−1;

(h) for each different portion of data in sequence, repeating steps (e) through (g) to form a scaled picture; and

(i) outputting the scaled picture from the destination memory.

2. The method of claim 1 wherein the first direction is a horizontal direction, and the second direction is a vertical direction.

3. The method of claim 1 wherein the first direction is a vertical direction, and the second direction is a horizontal direction.

4. The method of claim 1 wherein step (d) comprises applying a mirror boundary condition to the first buffer and filtering initial data in the first buffer to produce the initial data in the second buffer.

5. The method of claim 1 further comprising before scaling a last portion of the digital picture in the second direction, applying a mirror boundary condition to part of the digital picture scaled in step (f).

6. The method of claim 1 further wherein step (e) comprises omitting transfer of part of the digital picture for down-scaling.