
Graphics

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 

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 Hanning
filter Triangle
filter Quadratic
filter Point
filter Hermite
filter Box
the original
filter Kaiser
filter Catrom
filter Cubic
filter Lanczos
filter Hamming
filter Welsh
filter Parzen
filter Blackman
filter Bohman
filter Mitchell
filter Bartlett
filter Gaussian
As you see the default choice gives a very sharp and welldefined 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 upscaling
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

