Plugins that have the capability flag HWPLUG_CAPS_SAVEIMAGE set can register
one or more additional output image formats. The user will then be able to save images
in the output formats supported by the plugin. Plugins have to register new output
image formats by passing the name of a constant that should be used to access the new format.
For example, a plugin might choose to register a new output image format under the
constant #IMGFMT_CUSTOMFORMAT. Whenever the user calls SaveBrush() or SaveSnapshot()
now and passes #IMGFMT_CUSTOMFORMAT as the image format, Hollywood will ask the plugin to
save the image.