# What: This CGI script will:
#   * Accept a single parameter: 'usd_value'.
#   * Fetch the current exchange rate for USD vs BTC from mtgox.
#   * Calculate an amount of BTC to equal the value of the USD input.
#   * Return that value, rendered as a PNG image, normalized to 2 decimal places.
#
# Why:   Some people would like to advetrise goods for sale online and accept BTC as payment, yet want to base their pricing on USD currency.
#      To continually update BTC prices as the rate of exchange varies can be a chore.
#      With this script hosted on a web server, an advertiser can embed a reference to the script URL as an image, with their USD price target as a parameter.
#      A PNG image showing the appropriate value will be dynamically generated for each viewer, based on the current mtgox exchange rate.

I hope this is useful.

I would host it myself for people to use, but I'm having some trouble with my web host, and have been unable to install libgd onto it.

To use the script, you will need to have the perl modules CGI, LWP, JSON, and GD installed.  You will also need to have libgd installed.

Install libgd first.  I was able to install it on Ubuntu 10.04 using:

sudo apt-get install libgd2-xpm-dev

Then install the perl modules:

sudo perl -MCPAN -e 'install CGI, LWP, JSON, GD'

It will probably want to install some other modules that these depend on.

Here is the script:
http://www.illumina23.com/usd2btc/1.0/usd2btc.pl

If the script fails to execute giving 500 Internal Server Error, try executing it from the shell and see if you receive an error message:

$ ./usd2btc.pl

Is anyone else hosting this?  Perhaps a conversion based on the 24hour?