Method and Apparatus for Scaling Digitized Images

Method and Apparatus for Scaling Digitized Images

      Disclosed are DCT (Discrete Cosine Transform) based method and
apparatus for scaling digitized images.  Suppose an image is of size
MA x NB and we want to scale it to size PMA x QNB, where
A, B, PA and PB are small integers.  Typical examples are A = B =
8; to double the image size in each dimension we take P = Q =
2; to halve the image size in each dimension we take P = Q =
5.  The method proceeds as follows:
1.  Perform the Discrete Cosine Transform (DCT) on contiguous A x B
blocks of the original image.
2.  Convert each of the A x B blocks obtained in step (1) to a
PA x QB block by either deleting the bottom A(1 - P) rows if P
< 1, or padding with A(P - 1) rows if P > 1, and similarly
by either deleting the right-most A(1 - Q) columns if Q < 1, or
padding with A(Q - 1) columns if Q > 1.
3.  Perform the Inverse Discrete Cosine Transform (IDCT) on
contiguous PA x QB blocks of the output of step (2).

      Disclosed anonymously.