Tests the normal behaviour of the MedianCollection operation
using the JAI architecture. It tests the algorithm itself as well as the
presence and consistency (for rendered images) of the registration file
META-INF/registryFile.jai .
Each of the three image is 4 x 4 pixels. The first and third images have
the same pixels, a red [255 0 0] border and a purple [255 0 255] center
while the second image is the reverse, a purple border and a red center.