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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![Point scaling point.png](point.png) |
Box![Box scaling box.png](box.png) |
Triangle![Triangle scaling triangle.png](triangle.png) |
Hermite![Hermite scaling hermite.png](hermite.png) |
Hanning![Hanning scaling hanning.png](hanning.png) |
Hamming![Hamming scaling hamming.png](hamming.png) |
Blackman![Blackman scaling blackman.png](blackman.png) |
Gaussian![Gaussian scaling gaussian.png](gaussian.png) |
Quadratic![Quadratic scaling quadratic.png](quadratic.png) |
Cubic![Cubic scaling cubic.png](cubic.png) |
Catrom![Catrom scaling catrom.png](catrom.png) |
Mitchell![Mitchell scaling mitchell.png](mitchell.png) |
Lanczos (default)![Lanczos scaling lanczos.png](lanczos.png) |
Bessel![Bessel scaling bessel.png](bessel.png) |
Sinc![Sinc scaling sinc.png](sinc.png) |
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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![](upscaled/icon004_box.png)
-filter Kaiser![](upscaled/icon014_kaiser.png)
-filter Cubic![](upscaled/icon003_cubic.png)
-filter Triangle![](upscaled/icon007_triangle.png)
-filter Catrom![](upscaled/icon006_catrom.png)
-filter Quadratic![](upscaled/icon008_quadratic.png)
-filter Welsh![](upscaled/icon015_welsh.png)
the original ![](upscaled/original.png)
-filter Hamming![](upscaled/icon011_hamming.png)
-filter Mitchell![](upscaled/icon009_mitchell.png)
-filter Hanning![](upscaled/icon016_hanning.png)
-filter Parzen![](upscaled/icon012_parzen.png)
-filter Hermite![](upscaled/icon002_hermite.png)
-filter Lanczos![](upscaled/icon010_lanczos.png)
-filter Point![](upscaled/icon001_point.png)
-filter Bartlett![](upscaled/icon017_bartlett.png)
-filter Blackman![](upscaled/icon013_blackman.png)
-filter Bohman![](upscaled/icon018_bohman.png)
-filter Gaussian![](upscaled/icon005_gaussian.png)
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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