Q:

getImageData in Firefox 3 causing NS_ERROR_DOM_SECURITY_ERR

I'm trying to develop an application that will use getImageData in javascript in Firefox 3, but I am getting a "NS_ERROR_DOM_SECURITY_ERR" on the getImageData call. The javascript and the image are both currently being served from by hard drive, which is apparently a security violation? When this is live they will both be served from the same domain, so it won't be a problem, but how can I develop in the meantime?

A:

You can tell the browser to bug off.  The solution is better or worse depending on your circumstances.  I wrap it in a try so no security dialog will be presented if it's not an issue. 
  var data;
  try {
    try {
      data = context.getImageData(sx, sy, sw, sh).data;
    } catch (e) {
      netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
      data = context.getImageData(sx, sy, sw, sh).data;
    }
  } catch (e) {
    throw new Error("unable to access image data: " + e);
  }

A:

You could try installing a local webserver such as Apache (on unix) or IIS (on Windows).  That will ultimately give you the best local test bench for web-related stuff, because as you have found out browsers treat files from the filesystem quite differently than content served from a webserver.

