Editor Tool Utilities – Skeleton (Image Vectorisation)

local skeleton = require('editor/toolUtilities/skeleton')

-- Full pipeline: PNG to vectorised polylines with widths
local paths = skeleton.getPathsFromPng('/art/masks/road_network.png')
if paths then
  for i, path in ipairs(paths) do
    local points = path.points  -- array of vec3 (x, y pixel coords)
    local widths = path.widths  -- array of numbers (pixel widths)
    log('I', 'skel', string.format('Path %d: %d points', i, #points))
    -- Convert pixel coords to world space and create splines
  end
end

-- Low-level: skeletonise a mask manually
local mask = {}  -- 2D array of 0s and 1s, mask[y][x]
skeleton.skeletonise(mask)  -- modifies in-place to 1-pixel skeleton

-- Extract paths from skeleton
local rawPaths = skeleton.extractPaths(mask)

-- Estimate widths from original (non-skeletonised) mask
local widths = skeleton.estimateWidths(rawPaths, originalMask)

-- The pipeline internally:
-- 1. Loads PNG via GBitmap, flips Y
-- 2. Converts to binary mask with dynamic normalisation
-- 3. Dilates mask by radius 3 to thicken thin features
-- 4. Guo-Hall iterative thinning (two-phase deletion)
-- 5. Detects endpoints (1 neighbour) and junctions (3+ transitions)
-- 6. Walks arms between keypoints to extract path segments
-- 7. Filters short paths (< 20 pixels), joins close endpoints (< 40 px)
-- 8. Estimates widths by walking binormals in the original mask
-- 9. Tapers/smooths/clamps widths to reduce artifacts
-- 10. RDP simplification with tolerance 6.0