Join and slice tools

In CVAT you can modify shapes by either joining multiple shapes into a single label or slicing a single label into several shapes.

This document provides guidance on how to perform these operations effectively.

See:

• Joining CVAT labels
• Slicing CVAT labels

Joining masks

The Join masks tool (), is specifically designed to work with mask annotations.

This tool is useful in scenarios where a single object in an image is annotated with multiple shapes, and there is a need to merge these shapes into a single one.

To join masks, do the following:

1. From the Edit block, select Join masks .
2. Click on the canvas area, to select masks that you want to join.
3. (Optional) To remove the selection click the mask one more time.
4. Click again on Join masks (J) to execute the join operation.

Upon completion, the selected masks will be joined into a single mask.

Slicing polygons and masks

The Slice mask/polygon () is compatible with both mask and polygon annotations.

This tool is useful in scenarios where multiple objects in an image are annotated with one shape, and there is a need to slice this shape into multiple parts.

Note: The shape can be sliced only in two parts at a time. Use the slice tool several times to split a shape to as many parts as you need.

To slice mask or polygon, do the following:

1. From the Edit block, select Slice mask/polygon .
2. Click on the shape you intend to slice. A black contour will appear around the selected shape.
3. Set an initial point for slicing by clicking on the contour.
4. Draw a line across the shape to define the slicing path.
   Hold Shift to add points automatically on cursor movement.
   Note: The line cannot cross itself.
   Note: The line cannot cross the contour more than twice.
5. (Optional)> Right-click to cancel the latest point.
6. Click on the contour (Alt+J) (outside the contour) to finalize the slicing.