PHP - image sharpness comparision
<p>I need an algorithm to compare/rate the sharpness of given zones between two images.</p>

<p>For example:
Which image is sharper in the zone given?
Image1 - zone (x:10,y:10) to (x:100,y:100)
Image2 - zone (x:10,y:10) to (x:100,y:100)</p>

<p>the two zones coordinates may not be the same and the zones may vary in area/size. </p>
