Posted by
Kenneth Sloan-2 on
Jan 29, 2017; 8:53pm
URL: http://imagej.273.s1.nabble.com/cut-paste-w-arbitrary-warp-tp5017962.html
I’m about to write a Java plug-in to do cut&paste with arbitrary warp. As usual, I’d like to make sure I’m not re-inventing the wheel. Here are a few of the operations I have in mind:
[in most cases, there will be two images open - think of them as source and destination, although I may play a bit fast and loose with this]
For all operations, begin by outlining a (closed, simple) polygon) - P
a) specify 1 point in the source and 1 point in the destination. MOVE the pixels in P using simple TRANSLATION
b) specify 2 points (u,v) in the source and 2 points (s,t) in the destination, MOVE the pixels in P such that u maps to s and the direction from u->v maps to the direction s->t
c) specify2 points (u,v) in the source and 2 points (s,t) in the destination. MOVE the pixels in P such that u maps to s and v maps to t
Those are pretty simple - and those may be all I need for the immediate application. Now it becomes more complicated.
d) specify segment of P (begin at vertex v1 and end at vertex vn). Specify points w1 and wn in the destination. Move and scale the polyline v1..vn so that v1->w1 and v2->w2. Next, allow the user to perturb the vertices of the new polyline (within reason) to produce w1’..wn'. Finally, MOVE the pixels in P s.t. the entire polyline v1..vn maps to the perturbed poly line w1’..wn’ AND (the tricky part) the rest of the polygon warps “appropriately”.
e) special case of the above - map the entire bouncary polygon P to a copied and perturbed boundary w’, warping the interior as needed.
I think I’ve simplified some things by making the number of vertices in v and w (and w’) match exactly. Freeform specification of v and w is probably not that much harder to implement - but the end users will probably be thinking in terms of specific landmark POINTS rather than boundaries, per se.
Before someone asks, in all cases “MOVE the pixels in P” means “iterate over the pixels in the destination and fetch pixel values from the source.
So…my main question is: does this functionality exist anywhere?
And if so, where can I steal it.
Please note - I know how to do the warping and will (with some work) figure out how to implement the interaction. So, I don’t nee advice on appropriate methods (but…feel free to offer it anyway!).
I’m really just interested in whether or not there is an existing tool that does what I want.
Once past that - I welcome ideas on improving my specifications (either simplifying, or generalizing).
The specific applications is to repair artifacts generated in the creation of thin sections of human retina. The most serious problem with these is that some of the layers of the retina are fragile, and the tissue separates, with one part pulling away (with some warping and bending). The goal is to put it back together again, if only crudely. The matching doesn’t have to be terribly precise - the point is to create a correspondence between features found along the length of one part with features found along the length of the other (separated) part. Decisions about what warping is “reasonable” may well turn out to depend on the types of warping actually present. Mostly, this is a fairly simple separation and rotation. I anticipate some issues here near the pivot point, where the tissue remains attached. This may, or may not, be important.
And finally…I’ve gone to a generalized “cut and paste” because there may be several such “separation and movement” artifacts in the same section. I originally thought I could simply throw a mesh over everything and warp things back together - but, I’ve seen enough examples that I’m now going to count on a trained observer starting from one source image and doing successive “cut/paste/warp” operations to put things together manually.
We could *almost” do this by grabbing polygons and moving them using only translation and rotation - but again, examples demonstrate that some amount of local generalized warping will be necessary.
—
Kenneth Sloan
[hidden email]
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