I've done it!! Chuck the problem seems to lie in the fysical location of the histogram.php file. The example above is in a /temp/ map, I placed it there, and guess what, it works!!!
Strange? Yes!, Why? I don't know but does it matter, not to us. For an example surf here:
Mijn tong in iets lekkers. - WFC Foto Beeld, de interactieve foto site van Nederland (yes all is Dutch, but surf beneath the photo and see the link: Histogram, click and see the histo in a small new window.
Pffff I can use a druk, wodka seems to be the right choice I think.
Gerard