transform is an advanced method for directly manipulating the transformation matrix when drawing to this image. It is designed for advanced users, and not for beginners. For most cases, 'rotate', 'scale' and 'translate' are the best methods to use.
This method allows you to apply your own transformation matrix on this image, for when you draw to it.
This differs from 'setTransform', because that will replace that current matrix, where as this is multiplied against it.
It can be undone by calling the 'undoTransform', or 'clearTransforms' methods to remove all transformations which have been applied.