Annotation with brush tool

Guide to annotating tasks using brush tools.

With a brush tool, you can create masks for disjoint objects, that have multiple parts, such as a house hiding behind trees, a car behind a pedestrian, or a pillar behind a traffic sign. The brush tool has several modes, for example: erase pixels, change brush shapes, and polygon-to-mask mode.

Use brush tool for Semantic (Panoptic) and Instance Image Segmentation tasks.
For more information about segmentation masks in CVAT, see Creating masks.

See:

Brush tool menu

The brush tool menu appears on the top of the screen after you click Shape:

BT Menu

It has the following elements:

Element Description
Tick icon Save mask saves the created mask. The saved mask will appear on the object sidebar
Save mask and continue Save mask and continue adds a new mask to the object sidebar and allows you to draw a new one immediately.
Brush Brush adds new mask/ new regions to the previously added mask).
Eraser Eraser removes part of the mask.
Add poly Polygon selection tool. Selection will become a mask.
Remove poly Remove polygon selection substracts part of the polygon selection.
Brush size Brush size in pixels.
Note: Visible only when Brush or Eraser are selected.
Brush shape Brush shape with two options: circle and square.
Note: Visible only when Brush or Eraser are selected.
Pixel remove Remove underlying pixels. When you are drawing or editing a mask with this tool,
pixels on other masks that are located at the same positions as the pixels of the
current mask are deleted.
Label Label that will be assigned to the newly created mask
Move Move. Click and hold to move the menu bar to the other place on the screen

Annotation with brush

Prerequisites: Create task, upload the image, add labels, and open the workspace.

Do the following:

  1. From the controls sidebar, select Brush Brush icon.

  2. In the Draw new mask menu, select label for your mask, and click Shape.
    The BrushBrush tool will be selected by default.

    BT context menu

  3. With the brush, draw a mask on the object you want to label.
    To erase selection, use Eraser Eraser

    Brushing

  4. After you applied the mask, on the top menu bar click Save mask Tick icon
    to finish the process (or N on the keyboard).

  5. Added object will appear on the objects sidebar.

To add the next object, repeat steps 1 to 5. All added objects will be visible on the image and the objects sidebar.

To save the job with all added objects, on the top menu click Save Save.

Annotation with polygon-to-mask

Prerequisites: Create task, upload the image,
add labels, and open the workspace.

Do the following:

  1. From the controls sidebar, select Brush Brush icon.

  2. In the Draw new mask menu, select label for your mask, and click Shape.

    BT context menu

  3. In the brush tool menu, select Polygon Add poly.

  4. With the PolygonAdd poly tool, draw a mask for the object you want to label.
    To correct selection, use Remove polygon selection Remove poly.

  5. Use Save mask Tick icon (or N on the keyboard)
    to switch between add/remove polygon tools:

    Brushing

  6. After you added the polygon selection, on the top menu bar click Save mask Tick icon
    to finish the process (or N on the keyboard).

  7. Click Save mask Tick icon again (or N on the keyboard).
    The added object will appear on the objects sidebar.

To add the next object, repeat steps 1 to 5.

All added objects will be visible on the image and the objects sidebar.

To save the job with all added objects, on the top menu click Save Save.

Remove underlying pixels

Use Remove underlying pixels tool when you want to add a mask and simultaneously delete the pixels of
other masks that are located at the same positions. It is a highly useful feature to avoid meticulous drawing edges twice between two different objects.

Remove pixel

AI Tools

You can convert AI tool masks to polygons. To do this, use the following AI tool menu:

Save

  1. Go to the Detectors tab.
  2. Switch toggle Masks to polygons to the right.
  3. Add source and destination labels from the drop-down lists.
  4. Click Annotate.

Import and export

For export, see Export dataset

Import follows the general import dataset procedure, with the additional option of converting masks to polygons.

Note: This option is available for formats that work with masks only.

To use it, when uploading the dataset, switch the Convert masks to polygon toggle to the right:

Remove pixel