[R] geometric transformation

[jgarcia at ija.csic.es]

Hi everyone,

I've got a set of thousands points (2D) located on a pixel image, and I
know that four points in this pixels image correspond to four points in a
real space on which I need to locate the mapping of all the thousand
source points from the pixel set.
For this I've got four reference points (corners.px), and the
corresponding four destination points (corners.r):

> corners.px
      [,1]  [,2]
[1,] 212.5 275.5
[2,] 562.5 275.5
[3,] 212.5 625.5
[4,] 562.5 625.5

> corners.r
       [,1]  [,2]
[1,] 139463  8386
[2,] 139579 -1294
[3,] 131921  8180
[4,] 132002 -1256

I think I must find a transformation matrix and apply this transformation
matrix to all the set in the pixel space, but cannot find the way to
contruct this transformation matrix.
I guess this is not a question just pertaining to R, but perhaps you can
help me with this.

Thank you and best regards!

Javier
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