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Method and Apparatus for Scaling Digitized Images

IP.com Disclosure Number: IPCOM000107936D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 28K

Publishing Venue

IBM

Related People

Feig, E: AUTHOR

Abstract

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.

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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.