This is useful if, for example, you have an old version of imagemagick (because Debian is so slow to upgrade) and you want to force CMYK images into sRGB: ":colorspace => 'sRGB'"
… a different extension.
Extracted convert_command method to make spec easier to write. DRYed up regexes and improved them.
That was redundant anyway since method_missing() then defaults to quality of 100. Furthermore it was interfering with looking up a default from Paperclip.options (as it made it seem like a specific value was being requested).
…[:quality] This way you can set global defaults for these options, without needing to pass them in for each call.