By Tracy Colello
Start with any single layer fractal. For this example, add crackle, set it to 6, and cellsize= 0.1
Add a final crop_box. Set the size (for example width and height=3) and invert=1 Next, add another final crop_box (or post_crop_box on the same transform) Set the size (for example width and height=4) and invert=0 Last, add post_point_crop to get rid of the dot.
Other methods For squares: Final crop or crop_box plus post_smartcrop with a negative radius. Final linear3D with 2 post_smartcrops (can have rounded corners) For circles: Final circlecrop, final glynnsim3 with contrast=0 Final glynnsim3 with contrast=0 plus post_circlecrop
