How Can I Programmatically Detect the Color of a Specific Screen Pixel?

How to Detect the Color of a Screen Pixel

In this question, a user seeks a method to determine the color of a specific pixel on their screen. The ultimate goal is to trigger an action when a certain color is detected.

Finding the Efficient Solution

The most effective approach involves using the GetColorAt function to retrieve the pixel's color at a specific location. Unlike some other methods, this approach is independent of the number of monitors connected to the system.

Here's a C# code snippet that implements the GetColorAt function:

public Color GetColorAt(Point location)
{
    using (Graphics gdest = Graphics.FromImage(screenPixel))
    {
        using (Graphics gsrc = Graphics.FromHwnd(IntPtr.Zero))
        {
            IntPtr hSrcDC = gsrc.GetHdc();
            IntPtr hDC = gdest.GetHdc();
            int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, location.X, location.Y, (int)CopyPixelOperation.SourceCopy);
            gdest.ReleaseHdc();
            gsrc.ReleaseHdc();
        }
    }

    return screenPixel.GetPixel(0, 0);
}

Using the Pixel Color Information

With the GetColorAt function, you can now poll a specific pixel on the screen for a desired color. Here's an example of polling for a blue pixel:

private void PollPixel(Point location)
{
    while(true)
    {
        var c = GetColorAt(location);

        if (c.R == c.G && c.G  128)
        {
            DoAction();
            return;
        }

        Thread.Sleep()
    }
}

This code continuously polls the pixel at a specific location. When the pixel matches the blue criteria, it triggers the DoAction method.

Conclusion

Using the GetColorAt function, you can efficiently determine the color of individual screen pixels. With this capability, you can implement various image processing or screen detection tasks as required by your specific application.

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