Re : Affine Transformation on image

[thierry77]

I want to apply a affine transformation on a image. I know some (at least 3) points on the current image and the same points on the "new image" (after the affine transformation).

I can not use the function from matlab or opencv to perform the geometric operation and only find basic operation like rotation or translation in the vision module

[KevinC]

You should look at the calibration functions. An affine transform is a subset of the perspective transform that the calibration functions provide.

Kevin

[thierry77]

Thanks for your answer.

I actually manage to implement in labview the transformation affine and the estimation of its matrix, once I really understand the bilinear interpolation

[AlexanderKhodarev]

Sometimes it is easier to work with image in the form of 2D array (especially if you are working with grayscale image).

In that case Functions>>Mathematics>>Geometry pallet should be exactly what you need.

[ilanm]

Do you have a VI fo the affine tranformation? for 3 points?

[alexderjuengere]

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@ilanm wrote:

Do you have a VI fo the affine tranformation? for 3 points?

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Maybe kl3m3n posted something you're looking forward: https://decibel.ni.com/content/blogs/kl3m3n/2015/04/24/homography-mapping-calculation-labview-code

[Klemen]

Hello,

write the equation for affine transformation and solve it. You need 3 point pairs for this. If you have more points, you could use a least-squares approach.

If you don't like coding, you can use OpenCV's functions getAffineTransform() and estimateRigidTransform(), respectively. Just perform a .dll call - there are a lot of examples online.

Best regards,

K

[Klemen]

Hello,

to help you a bit further, here is an example of calculating the affine transformation (least square), provided you know the three corresponding point pairs.

Hope this helps.

Best regards,

K

[Dr._David]

Exactly what I was looking for.  Thank you!