[Insight-users] Puzzling registration result

[smythek at u.washington.edu]

Hello all,

I have two images, both 1300 x 1030, that I have registered.  There is about 40-50 pixel overlap between the bottom of the first and the top of the second.  I altered the ImageRegistration1.cxx example file to perform my registration, giving it an initial guess of (0, -1010) and it came back with translations (-2, -997) (I've forgotten the decimals exactly).

I used the PasteImageFilter to combine the two images, setting the "bottom" start point to be (2, 997), and at first I thought they were correctly composited.  But upon closer inspection, it appears that (2,997) is "too far" down into the top image, because I can clearly see repeated areas.  If I subtract 1 from the x direction and 43 from the y-direction, then the composited images are much better aligned.

Why didn't the registation give me the best transform?  Or if it did, what am I missing in setting up the pasteimagefilter start points?

Thanks,

Kathy