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ImageTool
See it work

Magic-wand selection

Click one pixel. Select the whole shape.

A click-seeded magic-wand image selector in pure C# - zero dependencies outside the .NET base library. Part of the OnlyCSharp educational library.

Animated magic-wand selection cycling through lamppost, flower, and outlet fixtures - input, yellow selection outline, then isolated cutout

The wand in motion: for each fixture it shows the input, the selected region (yellow outline), and the isolated cutout. Rendered and encoded entirely by OnlyCSharp's own GIF codec - round-trip verified (GIF89a, 9 frames, 120x90).

How it works

You click a pixel; the wand grows one contiguous region of pixels perceptually similar to that seed color, measured as a CIELAB dE tolerance flood fill. The raw mask is cleaned with a morphological close, then traced into a simplified silhouette outline via marching-squares contour stitching.

  • Lab-space tolerance flood - perceptual color distance, not raw RGB, so it follows what the eye reads as "the same color".
  • Morphological cleanup - closes pinholes and ragged edges in the selection mask.
  • Contour stitching - the one genuinely-new primitive; marching squares plus loop stitching plus polyline simplification into a clean vector outline.

Single selection, step by step

Input fixture: a flower on a plain background
1. Input
The raw synthetic fixture.
The same flower with the wand selection traced as a yellow outline
2. Wand selection
Traced outline of the flooded region.
The flower isolated on transparency as a clean cutout
3. Isolated cutout
Everything outside the mask removed.

Command line

The tool is a console app. The selection above was produced by:

imgtool wand input.png cutout.png --x 60 --y 45 --tolerance 12

Beyond the Tier-1 wand, later milestones add a GrabCut foreground segmenter (graph-cut min-cut over Gaussian color mixtures), a recognition layer (Hough lines + geometric shape descriptor), and a photo-to-3D inflation pipeline (Teddy silhouette inflation to a watertight, photo-textured solid) - all in pure C#.