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I'm not a pro in imagemagick. I have read documentation, but it has no use if you could not understand clearly how it works. I read in the wikipedia about lanczos filter and would like to try it for image resampling. So how could I use imagemagick to resample an image with lanczos filter in its purest form, without any pre- and post- processing?

From wikipedia reading and from sources that was published in the footnote links, I made an assumption that applying lanczos filter is just like any other kernel convolution and resampling in the middle is the only difference.

  • it would probably be better if you opened a new question and rollback to your original. As i can really see this little misunderstanding being asked quite many times. This way we can document your learning experience for others to follow. What do you think? – joojaa Jul 13 '16 at 15:52
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This question is somehow wrong in many ways but warrants an answer nonetheless to get you onto the right track.

There is no image when you have no post processing of the Lanczos filter. See the filter just turns the image into a continuous function. This in itself does nothing visible as this function needs to be used somehow to mean something

Img

Image 1: Filter makes discrete continious

In order for it to be an image again something has to be made to the continuous function to again turn it discrete. So you need to re-scale or otherwise transform and re-sample for this to make any sense. In essence make a new image, but without transform you just end with same image or if you miss-configure the filter you get a interesting blur.

a

Image 2: the process for a scaling re-sample.

  • Thanks for clarification. I edited the question to made it more clear – ayvango Jul 13 '16 at 13:57

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