The Magic Wand + Region Growing Tools¶

Overview¶

Selects pixels with a mouse click using one of two intensity-based methods, chosen from the Method dropdown.
Demo

Methods¶

Magic Wand¶

Selects all pixels that are connected to the clicked seed point and whose intensity lies within an adjustable range around the seed value. The range is defined by two Variation fields:

• left field — lower bound shift: pixels with intensity < seed − left are excluded
• right field — upper bound shift: pixels with intensity > seed + right are excluded

Connected pixels are found using MATLAB's bwselect at the selected connectivity (8/26 or 4/6 for 2D/3D).

Region Growing¶

Grows a region outward from the clicked seed point using a fast MEX-based algorithm (C. Wuerslin, University of Tübingen). A neighbouring pixel is added to the region if its intensity differs from the region's current mean intensity by no more than the Variation value. The region expands iteratively until no more pixels satisfy this criterion.

• Only the left Variation field is active in this mode.
• Connectivity is fixed internally (4-connected in 2D, 6-connected in 3D); the Connect radio buttons have no effect.

Widgets and parameters¶

• Method: select Magic Wand or Region Grow.
• Variation: intensity threshold relative to the seed value.
  • Magic Wand: left field = lower bound shift; right field = upper bound shift.
  • Region Growing: left field only — maximum intensity difference from the growing region's mean.
• Connect — 8 / 4: connectivity used by the Magic Wand - 8/26-connected (default) or 4/6-connected (2D/3D). Not used by Region Growing.
• Radius: limit the selection to pixels within this distance from the seed in pixels (0 = no limit).

Presets¶

Use the following key shortcuts to define and restore presets

• Shift+1, Shift+2, Shift+3 - store preset 1, 2, or 3 correspondingly
• 1, 2, 3 - restore preset 1, 2, or 3 correspondingly

Back to MIB | User interface | Panels | Segmentation