Mandelbrot set (600x600)

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MaxIt = 3000

The Boundary Tracing algorithm

The Boundary Tracing algorithm [1,2] makes use of the fact that there won't be areas of one color "inside" areas of a different color. This means, that if you trace the boundary of a region of a single color, then all the pixels inside that area will have that one color also. In the left image below only 13% of pixels are calculated and all the rest are simply flooded. But it is evident, that you can get wrong picture (to the right) for very large scale. Click this image to "repair" it.

[1] Michael R. Ganss "AlmondBread" (copy at
[2] John Bailey The Boundary Tracing algorithm

updated 15 November 2002