How to randomly jitter pixels?

[tomsvilans]

Hi, first post!

I've written a script that keeps an eye on a folder of images, resizes them as they are created (using ImageMagick) and outputs to a different folder. The problem is a very distinct moire pattern (because of the nature of the images) that simple resizing doesn't get rid of.

Is there a way to apply a random jitter to the pixels of the original high-rez images before resizing? I think this should help the moire pattern in exchange for a bit of grain / noise in the resized image, but I want to see how that would look. Is there a simple pixel filter that randomly moves pixels over by a set amount (1-2 pixels)?

Thanks!

[fmw42]

Hi, first post!

I've written a script that keeps an eye on a folder of images, resizes them as they are created (using ImageMagick) and outputs to a different folder. The problem is a very distinct moire pattern (because of the nature of the images) that simple resizing doesn't get rid of.

Is there a way to apply a random jitter to the pixels of the original high-rez images before resizing? I think this should help the moire pattern in exchange for a bit of grain / noise in the resized image, but I want to see how that would look. Is there a simple pixel filter that randomly moves pixels over by a set amount (1-2 pixels)?

Thanks!

See -spread
http://www.imagemagick.org/script/comma ... php#spread

In IM, you can do something similar with the very slow -fx to apply a random offset to each pixel coordinate. See the rand() function at http://www.imagemagick.org/script/fx.php.

convert rose: -fx "ii=i+10*rand(); jj=j+10*rand(); u.p{ii,jj}" show:


But there are other resizing filters that may perform better with regard to moire artifacts. See
http://www.imagemagick.org/Usage/filter/
http://www.imagemagick.org/Usage/filter/nicolas/