[Insight-users] Gradient Difference Metric

[Dan Mueller]

Hi Aviv,

2008/6/25 Aviv Hurvitz <aviv.hurvitz at gmail.com>:
> In short, the GradientDifferenceImageToImageMetric is bad! It has one huge
> bug and a few other debatable problems. The huge bug is that it returns the
> MAXIMUM value when the registered images are perfectly aligned, whereas it
> should return the MINIMUM. That's right, this metric actually pushes the
> moving image away from the right result.
>
> I wonder how this came to be? My guess is that the original developer was
> using it in a different framework, where registration involved maximizing. I
> Googled a bit and the few reports on this metric were either that it doesn't
> work or that it *maybe* works, so I guess it  checks out.

For future reference, this is not really a "huge" bug. Optimizers can
be configured to either minimize or maximize a metric; simply call
optimizer->MinimizeOn() or optimizer->MinimizeOff() depending on your
chosen metric.

HTH

Regards, Dan