My scenario is converting an existing PDF to an image. When the PDF contains an image with transparency the transparency is lost and the image is drawn at 100% opacity.
This fix is related (and depends on) the issue: https://issues.apache.org/jira/browse/PDFBOX-975
All that is needed is to set the composite of the graphics before drawing the image as specified in the graphics state (See attached patch)
Note: line number in patch maybe off since it was created from 1.5.0 but after fixing 975.