imgITools in Firefox 3.0

 decodeImageData
 Caller provides an input stream and mimetype. We read from the stream
 and decompress it (according to the specified mime type) and return
 the resulting imgIContainer. (If the caller already has a container,
 it can be provided as input to be reused).

 @param aStream
        An input stream for an encoded image file.
 @param aMimeType
        Type of image in the stream.
 @param aContainer
        An imgIContainer holding the decoded image. Specify |null| when
        calling to have one created, otherwise specify a container to
        be reused.

 encodeImage
 Caller provides an image container, and the mime type it should be
 encoded to. We return an input stream for the encoded image data.

 @param aContainer
        An image container.
 @param aMimeType
        Type of encoded image desired (eg "image/png").

 encodeScaledImage
 Caller provides an image container, and the mime type it should be
 encoded to. We return an input stream for the encoded image data.
 The encoded image is scaled to the specified dimensions.

 @param aContainer
        An image container.
 @param aMimeType
        Type of encoded image desired (eg "image/png").
 @param aWidth, aHeight
        The size (in pixels) desired for the resulting image.