Filling A Bitmap With A Color?

Ok basically I want to select a point on a bitmap and then fill all of the color that is the same as the color at that point touching that color with a different color. If that sounds confusing, just think of the paint bucket tool in mspaint or photoshop. Currently I do this by starting with the point selected and then check all the points around it in an ever expanding box until at last no new contiguous points of the color to replace are found.The bad news: This is slow as heck =(I remember my windows 98 computer could handle this just fine with no noticeable delay. So I'm either missing something algorithmically (is there a better approach) or VB.net is just too slow to accomplish this without some sort of different approach/optimization.

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As you can see, right now I just select the middle point as where I want to start filling from, and I fill with the color aquamarine. later I want to make this more flexible, but right now I just need this to be faster.

My general algorithm works like this:Start with a 3x3 pixel box with the first pixel (already changed to your new color, with the old color stored) as your start point.Check if each pixel is the color you stored (the one you're replacing) If it is, check if it's next to the new color you're replacing the old color with. If it is, replace it and increase the size of the box.The process ends when no new pixels are replaced.