[whataguy]

> Each pixel represents 2,500 ISBNs. If we have a file for an ISBN, we make that pixel more green.

What do you mean by "more green"? I don't see any shaded green.

And I presume the black pixels are unregistered ISBNs?

[slyall]

I'd suggest you try a color blindness test. The green is very obvious, especially about 40% of the way down the whole image.

[whataguy]

No, I see the green, but I don't see any shaded green. Though this has probably to do that ISBNs are distributed in blocks and every pixel is either red or green?

[lmm]

If you look closely there are definitely some brownish pixels and some dim greens.