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Converting the Resolution of an Image

IP.com Disclosure Number: IPCOM000114256D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 51K

Publishing Venue

IBM

Related People

Ioka, M: AUTHOR

Abstract

This article describes a method for converting the resolution of an image.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Converting the Resolution of an Image

      This article describes a method for converting the resolution
of an image.

      The problem is how to estimate the pixel value at (u(0), v(0))
in unconverted (u, v) coordinates corresponding to (x(0), y(0)) in
converted (x, y) coordinates, as shown in Fig. 1.  (u(0),v(0)) does
not correspond to the original pixel point in unconverted (u, v)
coordinates.  There are two types of resolution conversion,
enlargement and shrinking.  In case of enlargement, the ordinary
method is adopted.  However, in case of shrinking, the method
described below is adopted, as shown in Fig. 2.  To estimate pixel
value at (u(0), v(0)) in converted coordinates, following equation
(1) is used:

      &alpha.(k) is the ratio of the union of the area represented
by unconverted pixel (u(k), v(l)) and the area represented by the
converted point (u(0), v(0)) to the area represented by the converted
point (u(0), v(0)), as shown in Fig. 4.  The range of &alpha.(kl) is
0 < &alpha.(k) <= 1.  The above equation (1) is divided into the
following two equations (2),(3) for the u and v directions.

      &beta. and &gamma.  are the line segment ratios for the u and
v direction respectively.  The value of each &beta. and &gamma.  is
uniform.  Each &beta. and &gamma. is calculated in advance, as
shown in Fig. 3.  The conversion process is performed separately for
the u and v directions.