title: How to Downsize Images and Keep Them Sharp 
date:  20140731 13:27:28
tags:  #gimp #photos #webdev


When you size down an image you may get moires or jagged edges due to spatial frequency folding. The solution is to pre-blur the picture before sizing down. The rule is simple, if you size down by X, pre-blur with a Gaussian blur with a radius of X. For example, if you take an image from from 2000px to 400 (1:5), you would use a 5px blur radius.

Then resize your image with scale image (resize in PS) and apply smart sharpen to sharpen up the details.

This works because that pre-blur step (provided you do it right, using just enough, but not too much) doesn't end up softening the result any more than a direct downscale. If done correctly it removes information that will be lost in the resize anyway.

based on: http://gimpforums.com/thread-image-quality-and-resizing