Edge Routing in Graph Drawing

Whatever the algorithm is, whether or not it meets your requirement, but let me tell my trick to find the edge of object on the monitor.

Using a ready made application indeed a better way, but using your own algorithm is the best way for your brain and man kind. :-)

It was assumed that:
1. The object has solid color (no gradation)
2. The circumference has also solid but different color with the object.
3. The object and circumference being in a frame of rectangular shape on the monitor screen.
4. You want a line (or curve) that is a border for the object in whatever color you want. Let white is the color of the line. (The object and the circumference is not white, of course)

Here is the algorithm in simplest:
A. Horizontal Scanning
1. Do scan pixel by pixel in row and read its color
2. put the white dot when the pixel color changes
3. repeat the process for all the row

B. Vertical Scanning
1. Do scan pixel by pixel in column and read its color
2. put the white dot when the pixel color changes
3. repeat the process for all the column

The proces should superimposed for both the scanning proccess.

Have fun with your adventure, but watch your step!