Line and edge detection:

One simple test image :-)

Here is one image for testing line and edge detectors. It contains a vertical squarewave grating, a ring and two thin diagonal lines. Of course, you could write a 10 line program to detect all, but the fun is to apply Gabor and wavelet filters... If you are not convinced about the difficulty, just apply the Canny or Marr-Hildreth operators.
We used this image for developing a method which simultaneously detects lines and edges (Simultaneous detection of lines and edges using compound Gabor filters, J.H. van Deemter and J.M.H. du Buf, submitted to the Int J Pattern Recogn and Artificial Intelligence). Preliminary results using straightforward Gabor filters can be seen in my Biological Cybernetics' paper on Ramp edges, Mach bands etc (see my homepage dubuf for the reference). Along with the test image you can copy the correct event map, although the phase transition on the ring will depend on the number of filter orientations applied.

The file format is 256x256 bytes, 1 byte/pixel, grayscale gif. You can click on an image in order to download it in gif format, and you need to use xv or ImageMagick to convert it to raw format that you can read in your programs.

You are FREE to use these images in your work and publications, provided that you refer to us!

Test image

Event map

Please send comments to dubuf@ualg.pt.
Please visit the Vision Laboratory.
Last update: August 1997