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This section not yet updated for Inkscape v0.92.

SIOX

Simple Interactive Object Extraction or SIOX allows one to separate an object from the background in a bitmap image. It acts as a preselection routine for normal tracing. At the moment, only a background region can be specified. In the future, a foreground region will also be definable.

The performance of SIOX depends greatly on the characteristics of the bitmap image. Colored bitmaps where the object is clearly distinguished in color from the background work best.

To use SIOX, check the SIOX foreground selection box in the Trace Bitmap dialog. The label is a bit misleading as the next step is to select a region that includes the entire object of interest and excludes most of the background. The SIOX algorithm uses the excluded region to characterize the background.

Create a closed path around the object you wish to extract. Give the path a fill if it doesn't already have one. Select both the bitmap image and the path and then trace as usual.

SIOX tracing.
An example of using SIOX. Left, original bitmap image. Middle, image with background exclusion region added. Right, result of tracing. One can see that the background rejection is not perfect as there are similar colors in the background and foreground (e.g., reddish hair on chest).