Image: Lichtenstein img processing test

Description: I needed a test image to be used in some examples of image processing. In books and articles, Lenna is commonly used, but I can't use it on Commons because it is not in the public domain. I took a look at the featured pictures, and I have decided to use Image:Lichtenstein.jpg because it has several details (higher frequencies) in the bottom left and almost no details (lower frequencies) in the top right, plus sharp edges (between the castle and the sky). It's not as pretty as Lenna, but it's a good compromise! Moreover, it was not taken with a digital camera, so it does not show the typical artifacts due to Bayer pattern. Using GIMP, I have cropped the original image in order to have a squared picture, then I have downscaled it to 512x512 pixels using bi-cubic interpolation: this way the smaller image should have all the frequencies and the artifacts of the original JPEG compression should be negligible. I saved it in a lossless PNG to save the higher frequencies that could be removed by a JPEG compression. Those are the pictures I have created starting from this one:
Title: Lichtenstein img processing test
Credit: Image:Lichtenstein.jpg
Author: Andreas Tille, cropped by Alessio Damato
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC-BY-SA-3.0
License Link: http://creativecommons.org/licenses/by-sa/3.0/
Attribution Required?: Yes