fix(imageResliceMapper): adjust texel size calculation for anisotropi…

[sedghi]

Context

The label-outline thickness rendered by vtkImageResliceMapper appears inconsistent (stretched or compressed) when the input image has anisotropic spacing. This
happens because the texel-size uniform used for neighbor sampling in the outline shader is computed from voxel dimensions alone, ignoring the physical spacing of
each axis.

Results

Before: outline thickness varies per axis on anisotropic data — thicker along the axis with smaller spacing, thinner along the axis with larger spacing.

After: outline thickness is visually uniform across all axes regardless of spacing differences.

Changes

• Sources/Rendering/OpenGL/ImageResliceMapper/index.js: The texelSize uniform computation now divides by inputDims[i] * inputSpacing[i] instead of just
  inputDims[i], normalizing the texture-coordinate step by physical spacing so the outline kernel samples at consistent physical distances in all directions.

• No API changes.

• Documentation and TypeScript definitions were updated to match those changes

PR and Code Checklist

• semantic-release commit messages
• Run npm run reformat to have correctly formatted code

Testing

• This change adds or fixes unit tests
• Tested environment:
  • vtk.js:
  • OS:
  • Browser:

CC @PaulHax

[sedghi]

not sure if test failing in action my fault or not, since npm test runs fine locally

Update: updated the screenshot for test

[PaulHax]

Good fix.

This changes outline thickness from voxel space to physical space. The implication: small spacing produces thicker outlines, large spacing produces thinner ones for the same "outline thickness" paramter.

Current change is already better methinks, but i'm also consitering:

Normalize by the finest axis (minSpacing / (dims * spacing)) — keeps the anisotropy fix but thickness stays ~1 voxel on the finest axis.

or

Compute texelSize from the view-projection matrix so outlines are a fixed pixel width regardless of spacing or zoom

[sedghi]

@PaulHax please check it out

[PaulHax]

Looks good, outline thickness operating in "voxel" space makes sense to me.

[sedghi]

any chance we can merge this? @sankhesh

[finetjul]

LGTM

[github-actions]

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