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   -> Volume 5, Issue 5


Preprint: Overlapped Discrete Cosine Transforms for Image Compression
 
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Bob Henery bob@stams.strath.ac.uk
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PostPosted: Wed Dec 04, 2002 9:53 am    
Subject: Preprint: Overlapped Discrete Cosine Transforms for Image Compression
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Preprint: Overlapped Discrete Cosine Transforms for Image Compression

The following preprint is available for downloading from the Web as a
postscript file of 600k bytes:

http://www.stams.strath.ac.uk/~bob/overlap.ps

Title: Overlapped Discrete Cosine Transforms for Image Compression

Abstract:

Current research in image compression (wavelets, local trigonometric
bases, JPEG, etc.) centres on adaptive coding of the grey levels of
the image. These methods may be described as using band-limiting
procedures with a band-limit that depends on the local properties of
the image. This paper looks at the non-adaptive use of Discrete
Cosine Transforms in blocks, with uniform band-limits over the whole
image.

The relationship between compressed Cosine Transforms and
interpolation is used to establish a new type of lapped Cosine
Transform, allowing high compression of images without the well-known
``quilting" effect of JPEG-style compression. The method is
recommended whenever the end-product of compression is a low
resolution image: it is fast and easily programmed, and achieves
results comparable with the best wavelet compression methods.

There is also a compressed version of 100k bytes:

http://www.stams.strath.ac.uk/~bob/overlapnofigs.ps.Z

which also saves on bytes by omitting some images.

Bob Henery
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