Use the Boundary option to fill an area of the canvas delimited by another colour.

To use boundary fill:

1. Click Fill.

   The Fill controls appear.

   
   

2. Select the colour model and channels you want to work with.
3. Set the range for the fill in the Range field.
4. Enable Boundary.

   The Pick button is no longer greyed out.

5. Click Pick.

   The cursor changes to a colour picker when dragged over the image.

6. Drag the colour picker over the canvas without clicking.

   The various colour channel values in areas of the image are displayed as you move the colour picker around the canvas.

7. Click a point to select the colour for the boundary. You can also select a colour by entering the RGB values directly in the colour channel fields.

   The cursor changes to a paint bucket.

8. Click the area inside the boundary to fill that region.
   NoteTo fill a boundary with a reference image, set the Reference box to Front, Back, or Saved, and enable Medium.