When you use one of the Cutout tools to select an area of a sprite, you can erase the selected pixels so that they are transparent , or you can create a new sprite from the selection. When you extract or erase, the shape that you're drawing must be over the currently selected sprite - otherwise the extraction or erasure fails. Oval creates an oval selection. Curve creates a selection in a freeform shape with curved edges. After you create a shape with the Curve tool, you can edit its points to adjust the overall shape of the selection.
Polygon creates a selection in a freeform shape with straight edges.
After you create a shape with the Polygon tool, you can edit its points to adjust the overall shape of the selection. Click Stencil creates a new sprite that is an inverse of the selected sprite. The transparent pixels within the bounding box of the selected sprite are filled with the current colour in the new sprite, and the opaque pixels in the selected sprite are transparent in the new sprite. Use the tool on the Select Colour Region tab to select a portion of a sprite where the pixels have the same or a similar colour. Click to view Select Colour Region selects the pixel that you click on as well as the surrounding pixels that have the same colour.