It will work, even if the background isn't uniform, you'll just need the proper strategy that is generous enough to grab all of your greenscreen without replacing anything else.
Since at least some links on your linked page are dead, I tried my own approach:
The basics are simple: Compare the image pixel's color with some reference value or apply some other formula to determine whether it should be transparent/replaced.
The most basic formula would involve something as simple as "determine whether green is the biggest value". While this would work with very basic scenes, it can screw you up (e.g. white or gray will be filtered as well).
I've toyed around a bit using some simple sample code. While I used Windows Forms, it should be portable without problems and I'm pretty sure you'll be able to interpret the code. Just note that this isn't necessarily the most performant way to do this.
Bitmap input = new Bitmap(@"G:\Greenbox.jpg");
Bitmap output = new Bitmap(input.Width, input.Height);
// Iterate over all piels from top to bottom...
for (int y = 0; y < output.Height; y++)
{
// ...and from left to right
for (int x = 0; x < output.Width; x++)
{
// Determine the pixel color
Color camColor = input.GetPixel(x, y);
// Every component (red, green, and blue) can have a value from 0 to 255, so determine the extremes
byte max = Math.Max(Math.Max(camColor.R, camColor.G), camColor.B);
byte min = Math.Min(Math.Min(camColor.R, camColor.G), camColor.B);
// Should the pixel be masked/replaced?
bool replace =
camColor.G != min // green is not the smallest value
&& (camColor.G == max // green is the biggest value
|| max - camColor.G < 8) // or at least almost the biggest value
&& (max - min) > 96; // minimum difference between smallest/biggest value (avoid grays)
if (replace)
camColor = Color.Magenta;
// Set the output pixel
output.SetPixel(x, y, camColor);
}
}
I've used an example image from Wikipedia and got the following result:
Just note that you might need different thresholds (8
and 96
in my code above), you might even want to use a different term to determine whether some pixel should be replaced. You can also add smoothening between frames, blending (where there's less green difference), etc. to reduce the hard edges as well.