"extract" script for extraction. Many cases where a custom EXTRACT_CMD
simply copied the distfile into the work directory are no longer
needed. The extract script also hides differences between pax and
tar behind a common command-line interface, so we no longer need code
that's conditional on whether EXTRACT_USING is tar or pax.
Sharpening images with traditional methods increases the amount of
noise in the image. This script implements a method to sharpen images
described by Joern Loviscach in the german computer magazine c't,
22/1999.
Basically it "squeezes" unsharp edges. This method is a simplified
Version of an algorithm by Nur Arad and Craig Gotsman: "Enhancement by
Image-Dependent Warping", IEEE Transactions on Image Processing, 1999,
Vol. 8, No. 8, S. 1063.
