Contour Lines in Art
An explanation of Marr's zero-crossings.
For each picture, the original is first, and the result of the search for zero-crossings is second.
Vincent van Gogh's Starry Night.
Contains many long, complicated contours.
Wassily Kandinsky's Composition 6
Many complicated shapes, edges
Piet Mondrian's Composition with Red, Yellow, and Blue
The structure of the painting remains evident.
Georges Seurat's Le port de Gravelines
You can still make out many details of the picture