The spec of java.awt.image.FilteredImageSource.startProduction()
public void startProduction(ImageConsumer ic)
Adds an ImageConsumer to the list of consumers interested in data for this image, and immediately
starts delivery of the image data through the ImageConsumer interface.
This is spec is exactly the same as startProduction() method in
MemoryImageSource. However, from looking at the source code, the main body
of startProduction() in FilteredImageSource is to delegate the startProduction()
method to the ImageSource that is registered through its constructor.
This should be specified.