🚀 go-pugleaf

In article <1d3ji1INN759@cs.tut.fi>, defee@tukkasotka.tut.fi (Irek Defee) writes:
|> 
|> I would like to know present state-of-the-art in algorithms for
|> high-quality image z o o m i n g, especially for scaling-down, but
|> also for scaling up, by any factor. That is, how to diminish/enlarge an
|> image, with minimum perceptual quality loss, from (x1,y1) to (x2,y2) pixels?
|> This seems to be easy using photographic enlarger, but not so easy
|> in general with digital images. On the other hand, such things are 
|> running on computer displays.
|> 
|> Any info on (clever) algorithms, current implementations, references
|> and review material will be appreciated.
|> 
|> 
|> Irek Defee
|> Signal Processing Laboratory,
|> Tampere University of Technology,
|> Tampere, Finland.
|> Email: defee@cs.tut.fi
|> Fax: +358-31-161857
|> Voice: +358-31-162696


Scaling down is easy, just low-pass filter and decimate. Scaling up on computer
displays is usually done by just repeating pixels. Better results can be 
obtained by bilinear interpolation with some loss in resolution however. Good
results can be obtained by interpolation followed by a good (many taps) low-pass
filter. The fractal technique pioneered by Barnsley (see article by A. Jacquin,
IEEE Trans. Image Processing, Jan 1992) can give very pleasing effects when 
used for magnification.

-Ashok Rao (Comsat Laboratories)