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