Prime Shapes

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It is very common for artists of all ages and all skill levels to sketch out objects in a scene by combining basic shapes. This practice was formalised by artists, notably Leger but also Picasso and many other 20th century  Western painters. In addition, physiologists such as Biederman suggest people decompose complex objects into parts that have a simple geometry.


The work set out to discover if there is evidence for regions of simple geometry shape commonly occuring in segmentations of real-world images. Given the fact artists (pretty much anyone who draws) assembles complex objects from simple ones, we’ve chosen to call such shapes,  “prime shapes” .


Using three different segmentation algorithms, three different databases, and two different ways to characterise solid binary shapes we found evidence that prime shapes do occur.Moreover, these prime shapes can be named - triangle, square, circle, and so on. In some cases up to 80% of segments can be classified as “prime”. We used no supervision and no free parameters.


Q. Wu and P. Hall, Prime Shapes from Natural Images. BMVC 2012

An unintended but useful application. Prime shapes used to recognise scene types by the ratio of different shapes. Prime shapes in the left, state of art method (Aude Oliver) right.

Experimental Framework

Experimental Results

tall

inner

street

highway

coast

open

mountain

forest