Provide access to data offset in WritableRaster in Java 9

[Peter A]

Apologies since this probably not the correct list, but I was referenced
here from another Java list.

Background:
The high level API in a BufferedImage is very very very slow.  To get
around that problem, in previous versions of Java, the internal rasters
which were defined in sun.awt.image were accessed.   Doing so enabled
real-time computer vision in Java.

Problem:
Accessing the low level Rasters is no longer practical in Java 9.  After
this problem was reported by one of my users I looked into it and found a
work around, for most situations.  Unfortunately the higher level
WritableRaster does not provide access to the offset inside its internal
data array.   This makes processing of subimages impossible.  My suspicion
is that it is most likely an oversight because it provides access to every
other piece of information needed and the raw data.    It would be great
if getDataOffset() could be moved into WritableRaster or one of its parents
instead of being hidden in children of WritableRaster.

Just to clarify the raw arrays are stored inside of a DataBuffer and that
data structure contains an offset. This offset is always set to zero and
the offset inside of WritableRaster is what is needed,
e.g. IntegerInterleavedRaster.getDataOffsets().

Thanks,
- Peter

-- 
"Now, now my good man, this is no time for making enemies."    — Voltaire
(1694-1778), on his deathbed in response to a priest asking that he
renounce Satan.