[Insight-users] Freeman Coding Version in itk::ChainCodePath2D?

[Constantine Zakkaroff]

Hello ALL.

I attempted to read a 2D Freeman-encoded myocardial contour into a 
itk::ChainCodePath2D path from a file produced by QMass MR 6.2.1 and 
discovered that I had to remap encoded steps while reading them from the 
contour file before inserting them into the path object like this:

case '1': step = 3; break;
case '2': step = 2; break;
case '3': step = 1; break;
case '4': step = 8; break;
case '5': step = 7; break;
case '6': step = 6; break;
case '7': step = 5; break;
case '8': step = 4; break;
case '0': step = 3; break;

So it appears that in itk::ChainCodePath2D step encoding varies from the 
original paper "On the encoding of arbitrary geometric configurations", 
H. Freeman; IRE Trans. Electron. Comput, 1961. 
<http://ieeexplore.ieee.org/iel5/4037753/5219177/05219197.pdf>.

Was the choice in itk::ChainCodePath2D implementation geared towards 
some particular Freeman coding version/application?

Thanks,
Constantine