# Mapping CPR image pixel coordinates back to world coordinates with vtkImageCPRMapper

**URL:** https://discourse.vtk.org/t/mapping-cpr-image-pixel-coordinates-back-to-world-coordinates-with-vtkimagecprmapper/15627
**Category:** vtk.js
**Created:** [May 15, 2025, 2:02am UTC](https://discourse.vtk.org/t/mapping-cpr-image-pixel-coordinates-back-to-world-coordinates-with-vtkimagecprmapper/15627 "2025-05-15T02:02:48Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![buls\_brown](https://discourse.vtk.org/user_avatar/discourse.vtk.org/buls_brown/32/9254_2.png) [@buls\_brown](https://discourse.vtk.org/u/buls_brown)
#### Post date: [May 15, 2025, 2:02am UTC](https://discourse.vtk.org/t/mapping-cpr-image-pixel-coordinates-back-to-world-coordinates-with-vtkimagecprmapper/15627/1 "2025-05-15T02:02:48Z")

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Hi,

I’m using vtkImageCPRMapper to generate a curved planar reformation (CPR) image from my 3D volume along a centerline polyline. Now I’d like to take a pixel coordinate (u,v) in the resulting CPR image and find the corresponding (x,y,z) point in the original volume’s world coordinate system.

What’s the recommended VTK-based workflow or helper methods to perform this mapping?

Is there a built-in function in VTK that given (u,v) returns the world coordinate, or do I need to implement the steps manually?

Any pointers to example code or relevant VTK utilities would be greatly appreciated!

Thanks in advance,

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### Author: ![finetjul](https://discourse.vtk.org/user_avatar/discourse.vtk.org/finetjul/32/154_2.png) [@finetjul](https://discourse.vtk.org/u/finetjul)
#### Post date: [May 15, 2025, 2:29pm UTC](https://discourse.vtk.org/t/mapping-cpr-image-pixel-coordinates-back-to-world-coordinates-with-vtkimagecprmapper/15627/2 "2025-05-15T14:29:23Z")

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You might want to look at vtkCPRManipulator class implementation. There might be some useful information there.

Hth,  
Julien.