Downsampling with ImageMagick

Started Jan 10, 2012 | Discussions thread
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Downsampling with ImageMagick
Jan 10, 2012

A tip from http://www.openphotographyforums.com/forums/showthread.php?t=14947 is to create a txt file, rename to XXXX.BAT and put into your desktop, to resize just drag&drop the image into the icon.

My versions for downsampling are:

convert %1 -filter Lanczos -sampling-factor 1x1 -quality 90 -resize 1024 "% n1_1024.jpg"

For a soft downsample with ZERO ringing

convert %1 -filter Mitchell -sampling-factor 1x1 -quality 90 -resize 1024 "% n1_1024.jpg"

For something between Lanczos and Mitchell, Catrom is a good bet

convert %1 -filter Catrom -sampling-factor 1x1 -quality 90 -resize 1024 "% n1_1024.jpg"

Here 2 ready examples, just save into your desktop
http://www.mediafire.com/?ceeo1lecx3ec3u4
http://www.mediafire.com/?std5bzv2ehffdcu

This image http://www.mediafire.com/?49ahiwm5ukfu6c9 is a good candidate for testing resize algorithms, bad algorithms will create moiré...

Also look http://www.cambridgeincolour.com/tutorials/image-resize-for-web.htm

ImageMagick can also apply USM to the files by adding -unsharp 1.5x1+0.7+0.02

convert %1 -filter Lanczos -sampling-factor 1x1 -unsharp 1.5x1+0.7+0.02 -quality 90 -resize 1024 "% n1_1024.jpg"

More details in http://redskiesatnight.com/2005/04/06/sharpening-using-image-magick/

All about ImageMagick resize http://www.imagemagick.org/Usage/resize/

Btw, for the Photoshop centric guys, there is an interesting plug-in that creates a sharp(but with ringing) images http://www.fsoft.it/imaging/en/default.htm

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