Edges, corners, colors, etc.
This web page demonstrates some simple image processing operations
based on image gradients and colors.
The image gradient (at a particular point (x,y) in an image, along some
direction (u,v)) is defined as the rate at which the image intensity
changes as we move from (x,y) an infinitesimal distance in the
direction (u,v). The image gradient at (x,y) (without specifying
a direction) is the vector (gx, gy) such that the gradient in the
direction (u,v) is (gx*u+gy*v). Here are some screenshots of an image gradient explorer to help provide some
intuition about image gradients.
Using image gradients, we can build edge and
corner detectors and use them to locate structures within
images. For example, here is a demonstration of how to find barcodes in an image.
Here is the image used in the examples. It was taken with a Kodak
DC4800 at minimum resolution (1080 by 720), with standard settings
except for manual white balance (chosen so that white paper in full
sunlight from the window looks white), and saved as a JPEG with the
camera's standard options.
Here is the matlab source for the
demonstrations, and some simple targets to print out and track.
This page is maintained by Geoff
Gordon and was last modified on
June 16, 2004.