Flood Fill Algorithms in C# and GDI+

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<about id="Linear">LINEAR ALGORITHM
The linear algorithm first finds the horizontal extent of the color on a given level, then it loops across initializing the fill loop upwards and downwards for each point along the way. 

By handling vertical and horizontal checking separately, this algorithm consumes only half the stack space that the recursive algorithm uses, while avoiding the extra heap space needed for a queue.  It is also just as fast as the recursive algorithm.
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<about id="Queue">QUEUE ALGORITHM
The queue algorithm is similar to the recursive algorithm, except that it adds the points to be checked to a queue rather than calling them directly.  The loop returns immediately to the main fill method, rather than calling itself recursively.  It requires extra heap space for a queue, but it uses hardly any stack space.  

The queue algorithm is by far the slowest algorithm, taking about twice as long as the others.  This may be partly because of lack of optimizations in the .NET Queue class, but the queue method would be slower regardless of whether the Queue class was optimized.

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<about id="Recursive">RECURSIVE ALGORITHM
This is the most common, and simplest to implement.  The recursive algorithm branches in all directions at once.  This can (read: often will) lead to stack overflows in a managed environment.
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