Support ARC
Fix issue caused by CIImage size double after add filer.

There might be bugs in CIImage, that the size is doubled after add
filter.  Some defects for retain, maybe.

Replace drawImage:atPoint:fromRect with drawImage:inRect:fromRect, to
overcome the problem.

It will not lead to defect, when the bug of CIImage is fixed in the
future.
Merge pull request #1 from slavikshen/master

Support ARC