distance transform: use real intermediate array when pixel pitch is real
distance transform: use real intermediate array when pixel pitch is real

hmeine/vigra,dstoe/vigra,cha007/vigra,funkey/vigra,hmeine/vigra,stuarteberg/vigra,stuarteberg/vigra,xiwei-zhang/vigra,ThomasWalter/vigra,dstoe/vigra,funkey/vigra,cha007/vigra,kod3r/vigra,martinsch/vigra,hmeine/vigra,dagophil/vigra,mmuellner/vigra,cbecker/vigra,funkey/vigra,ThomasWalter/vigra,stuarteberg/vigra,funkey/vigra,psteinb/vigra,kod3r/vigra,dagophil/vigra,stuarteberg/vigra,DaveRichmond-/vigra,hmeine/vigra,cbecker/vigra,psteinb/vigra,capturePointer/vigra,mmuellner/vigra,DaveRichmond-/vigra,xiwei-zhang/vigra,cha007/vigra,capturePointer/vigra,kod3r/vigra,dstoe/vigra,stuarteberg/vigra,cbecker/vigra,martinsch/vigra,dstoe/vigra,kod3r/vigra,funkey/vigra,timoMa/vigra,cbecker/vigra,cha007/vigra,funkey/vigra,dagophil/vigra,DaveRichmond-/vigra,kod3r/vigra,DaveRichmond-/vigra,dagophil/vigra,hmeine/vigra,capturePointer/vigra,dstoe/vigra,mmuellner/vigra,DaveRichmond-/vigra,cbecker/vigra,stuarteberg/vigra,xiwei-zhang/vigra,ThomasWalter/vigra,martinsch/vigra,stuarteberg/vigra,dstoe/vigra,xiwei-zhang/vigra,mmuellner/vigra,capturePointer/vigra,ThomasWalter/vigra,psteinb/vigra,psteinb/vigra,ThomasWalter/vigra,timoMa/vigra,mmuellner/vigra,DaveRichmond-/vigra,DaveRichmond-/vigra,hmeine/vigra,timoMa/vigra,dagophil/vigra,cha007/vigra,funkey/vigra,xiwei-zhang/vigra,xiwei-zhang/vigra,psteinb/vigra,kod3r/vigra,timoMa/vigra,dagophil/vigra,capturePointer/vigra,capturePointer/vigra,martinsch/vigra,ThomasWalter/vigra,psteinb/vigra,mmuellner/vigra,cha007/vigra,psteinb/vigra,martinsch/vigra,cha007/vigra,timoMa/vigra,xiwei-zhang/vigra,dagophil/vigra,hmeine/vigra,mmuellner/vigra,cbecker/vigra,capturePointer/vigra,dstoe/vigra,ThomasWalter/vigra,timoMa/vigra,kod3r/vigra,martinsch/vigra,timoMa/vigra