Posted by
Kenneth Sloan-2 on
Apr 23, 2018; 1:38am
URL: http://imagej.273.s1.nabble.com/registering-a-stack-advice-needed-tp5020546.html
I have an application which needs to do MINOR corrections to images in
a Stack in order to register them. The modifications involve TRANSLATION,
some ROTATION, and SCALING (perhaps anisotropic).
So far, SIFT has been what I've been using.
My problem is that all of the above transformations are small - but I
don't know how to limit the allowed ROTATION (in particular). ROTATION
is the problem child, because the one way that SIFT produces ridiculous
results is to rotate a given image by 90deg - presumably because it finds
some accidental arrangement of features that makes it look like this is a good
idea.
SIFT allows you to specify a limit on the number of pixels to MOVE - but this does not
seem to constrain the ROTATION.
So...bottom line: I'm looking for advice on other methods to try.
The key requirement is that I'd like to allow TRANSLATION, anisotropic SCALE,
and ROTATION - even arbitrary local warping. BUT, I would also like to put
strict limits on "how much" of each is allowed.
As a rough guideline - I'd say that I need to limit:
TRANSLATION - no more than 25 pixels (in a 750x750 image)
SCALE - in the range [.9, 1.1] in x and y (independent)
ROTATION - no more than 10deg
Now...I naively thought that specifying "25 pixels max" would do the trick,
but I occasionally see results where the image is rotated 90deg, and "matching features"
are hundreds of pixels apart. Is this expected? or is it a bug?
I can supply an example pair of images that exhibits this behavior - on request.
My current workaround is to specify "translation only" with a maximum of 25 pixels of motion,
and am living with the slight inaccuracies due to the lack of scaling & rotation. As noted
above, the (spatial) differences between images in the stack are small, so this is
not a tragedy. [the gray-scale differences can be huge - this is "multi-modal imaging".
--
Kenneth Sloan
[hidden email]
Vision is the art of seeing what is invisible to others.
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