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Graphics
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ImageMagick downscaling algorithms
When working with ImageMagick, you can use the -filter option
to specify which kind of filtering you want. Here are the types of
filtering possible:
Point |
Box |
Triangle |
Hermite |
Hanning |
Hamming |
Blackman |
Gaussian |
Quadratic |
Cubic |
Catrom |
Mitchell |
Lanczos (default) |
Bessel |
Sinc |
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Now I will try to run all the scaling methods mentioned on ImageMagick's documentation page to see what they look like.
I'm scaling them up by a factor of 1.62857 for the worst possible result.
-filter Box
-filter Kaiser
-filter Cubic
-filter Triangle
-filter Catrom
-filter Quadratic
-filter Welsh
the original 
-filter Hamming
-filter Mitchell
-filter Hanning
-filter Parzen
-filter Hermite
-filter Lanczos
-filter Point
-filter Bartlett
-filter Blackman
-filter Bohman
-filter Gaussian
As you see the default choice gives a very sharp and well-defined nice
downscaling of the original.
Definately a good choice. It would be
nice to know more about what the different algoritms are good at though, as the
difference between all of them is not entirely obvious.
When i get the time i will expand this test with examples of up-scaling
to further investigate and display the nature of the different algorithms.
See also the browser scaling page on more general info about different scaling algorithms.
Website by Joachim Michaelis
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