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The Brush Tool

BigData mode: supported

The Brush works with BigData datasets. Strokes are applied at the displayed pyramid level and propagated to all resolution levels on disk.

Overview

Brush Tool

Use the brush to make selections, with size regulated by the Radius, px edit box

Controls
  • Ctrl + Mouse wheel: change brush size.
  • None or Shift + : paint with brush. In the Watershed / SLIC modes, Shift paints the stroke as a standard brush, without snapping to superpixels.
  • Ctrl + : start eraser (radius amplified by Eraser, x).
  • Auto fill in the Selection and View settings panel: autofill areas after brushing.

Tip

Connect objects across slices using Interpolation (i shortcut or Ribbon → Selection -> Interpolate).

Widgets of the brush panel

  • Radius: define brush radius in pixels.
  • Eraser, x: define eraser size multiplier.
  • Fix to screen: when checked, the brush radius is measured in screen pixels rather than image pixels. The cursor circle stays the same size on screen regardless of zoom — zooming in paints fewer image pixels (fine detail), zooming out paints more.
  • Interpolation Settings Interpolation settings: modify settings via dialog (also adjustable in
    Ribbon → Home -> Preferences -> Segmentation tools
    or in toolbar).
  • No clusters: the standard mode, selection of pixels under the brush cursor.
  • Watershed: cluster pixels with the watershed algorithm for selection as clusters.
  • SLIC: cluster pixels with the SLIC algorithm for selection as clusters.
Superpixels with the Brush tool

Enable Superpixels mode with Watershed or SLIC checkboxes. The brush selects groups of pixels (superpixels) instead of individual pixels.
Hold Shift while drawing to paint that stroke with the standard brush instead, which is handy for touching up a border that the superpixels do not follow. The eraser (Ctrl) always works pixel-wise as well.
Undo the last superpixel with Ctrl + Z.

Algorithms:

Adjust superpixel size and shape with

  • N (default, 220 for SLIC, 15 for Watershed)
  • Compact/Invert (higher compactness = more rectangular shapes; Invert: 1 for dark boundaries, 0 for bright).

Tip

Use
Ctrl + Alt + mouse wheel or
Ctrl + Alt + Shift + mouse wheel to adjust N.

Example of SLIC and Watershed superpixels

Example of SLIC and Watershed superpixels

SLIC boundaries use drawregionboundaries.m by Peter Kovesi.

Note

  • Note: Requires compiling slicmex.c for your OS.

References

  • Achanta et al., SLIC Superpixels Compared to State-of-the-art Superpixel Methods, IEEE TPAMI, 2012.
  • Achanta et al., SLIC Superpixels, EPFL Technical Report, 2010.

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

Each preset stores the Radius, Eraser, x, Fix to screen state, and clustering mode.

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