I know you can have too much of a good thing, but I do find Google Print pretty interesting :-) Here’s a quick run-down of the URL parameters they are using, and what they do. (Note that the service currently appears to be Slashdotted, with 502 Server Errors popping up everywhere. Surprising to get that from a company of their size, but there you go.)
- id: specifies the book.
- pg: specifies the page number. If you remove it, you get a list of all the pages in the book. But you can’t just increment it, because…
- sig: some sort of hash which also uniquely identifies the page. This is presumably to stop robots spidering the site and just monotonically increasing the page number.
- q: query – the words in this parameter will get highlighted in yellow. This indicates that they are generating the JPEG graphics on-the-fly from a computer-readable source on the back end. I suspect they’ve implemented display engines for several common book print formats.
Earlier today, URLs requires “img=<something>“, but they don’t seem to now. Instead, an lpg parameter has appeared. I’m not sure exactly what that does (why does it need two page numbers?), and I can’t investigate until they fix the server…