Handle single and two-point contours in slice mask generation

[drsantam]

Add support for contours with fewer than 3 points by drawing circles for single-point contours and lines for two-point contours, instead of attempting to fill them as polygons which would fail.

Summary by CodeRabbit

• Bug Fixes
  • Improved contour handling in mask generation, with enhanced support for single-point markers and line-based contours for more accurate mask slice processing.

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[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Modified the get_slice_mask_from_slice_contour_data function to handle contours conditionally based on point count. Single-point contours now draw as pixel markers via cv.circle, two-point contours as lines via cv.line, and multi-point contours are collected and filled using cv.fillPoly.

Changes

Cohort / File(s)	Change Summary
Contour Drawing Strategy Refactor rt_utils/image_helper.py	Replaced single-pass cv.fillPoly logic with per-contour conditional drawing: 1-point contours use cv.circle, 2-point use cv.line, 3+ points use cv.fillPoly. Improves handling of edge-case small contours.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant get_slice_mask_from_slice_contour_data
    participant slice_mask

    rect rgb(220, 240, 255)
        Note over get_slice_mask_from_slice_contour_data: Old Approach
        Caller->>get_slice_mask_from_slice_contour_data: Call with contours
        activate get_slice_mask_from_slice_contour_data
        get_slice_mask_from_slice_contour_data->>get_slice_mask_from_slice_contour_data: Collect all contours
        get_slice_mask_from_slice_contour_data->>slice_mask: cv.fillPoly (all at once)
        deactivate get_slice_mask_from_slice_contour_data
    end

    rect rgb(240, 255, 240)
        Note over get_slice_mask_from_slice_contour_data: New Approach
        Caller->>get_slice_mask_from_slice_contour_data: Call with contours
        activate get_slice_mask_from_slice_contour_data
        loop for each contour
            get_slice_mask_from_slice_contour_data->>get_slice_mask_from_slice_contour_data: Check point count
            alt 1 point
                get_slice_mask_from_slice_contour_data->>slice_mask: cv.circle (pixel marker)
            else 2 points
                get_slice_mask_from_slice_contour_data->>slice_mask: cv.line (line segment)
            else 3+ points
                get_slice_mask_from_slice_contour_data->>get_slice_mask_from_slice_contour_data: Collect for batch
            end
        end
        get_slice_mask_from_slice_contour_data->>slice_mask: cv.fillPoly (collected only)
        deactivate get_slice_mask_from_slice_contour_data
    end

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Single file with localized logic changes in one function
• Conditional branching added based on contour point count
• Verify the drawing methods (cv.circle, cv.line, cv.fillPoly) are used correctly with appropriate parameters
• Confirm edge cases (empty contours, invalid coordinates) are still handled properly

Poem

🐰 Contours dance in different ways,
One point circles, two points blaze,
Three or more we batch and fill,
Masks now drawn with finer skill!

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 8b312ee and fbdb0d1.

📒 Files selected for processing (1)

• rt_utils/image_helper.py (1 hunks)

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