PDImageXObject based on WritableImage

The goal is to work with a WritableImage from JavaFX in addition to a BufferedImage from Swing.

My proposal for a new feature are the following.

To extend the factory classes:

• CCITTFactory by the method:
  createFromImage(PDDocument document, WritableImage image)
• JPEGFactory by the methods:
  createFromImage(PDDocument document, WritableImage image)
  createFromImage(PDDocument document, WritableImage image, float quality)
  createFromImage(PDDocument document, WritableImage image, float quality, int dpi)
• LosslessFactory by methods:
  createFromImage(PDDocument document, WritableImage image)

To extend the PDImageXObject class:

• by the methods:
  getWritableImage()
  getWritableImage(Rectangle region, int subsampling)

Until now there is a need to use the class SwingFXUtils to do the conversion from WritableImage to BufferedImage or vice versa.
This new feature should come in handy for all JavaFX developers.