Convert PNG with alpha to JPG assumes black background

[lasconic]

Trying to convert the following image to JPG will send back a completely black image.

I'm tempted to add something like the following in image.js. Any advice?

if (image.outputFormat === 'jpeg') {
      r.background('#FFFFFF').flatten();
    }

[teohhanhui]

I think the background color should be included as a modifier.