This Edit menu command constructs a picture that is the image of a given picture cropped to its intersection with a given polygon. Use this command to isolate interesting portions of larger pictures. (For example, you could isolate some pattern or shape you’d like to tessellate using transformations.) Dynamically change the cropped picture by changing how the cropping polygon overlaps the original picture (for example, by dragging the polygon’s vertices). A cropped picture does not exist when its cropping polygon doesn’t intersect the picture.
When you create a cropped picture, Sketchpad hides the original picture and places the cropped picture on a layer above the polygon, so you can better see the cropped result. You can reveal the original picture using Display | Show All Hidden or the Information tool.
The Crop Picture to Polygon command is object-sensitive, so it may read Crop Picture to Triangle or Crop Picture to Pentagon, depending on the selected polygon.