How Can I Detect Screen Pixel Color Changes and Trigger Events?

Reading Screen Pixel Color for Event Triggering

Problem Statement:

Determing a method for capturing the color of a specific screen pixel and triggering an event based on the detected color.

Solution:

The most efficient technique involves capturing the pixel at the cursor location, ensuring compatibility across multiple monitors.

Detailed Implementation:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace ScreenPixelReader
{
    public partial class Form1 : Form
    {
        [DllImport("user32.dll")]
        static extern bool GetCursorPos(ref Point lpPoint);

        [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
        public static extern int BitBlt(IntPtr hDC, int x, int y, int nWidth, int nHeight, IntPtr hSrcDC, int xSrc, int ySrc, int dwRop);

        public Form1()
        {
            InitializeComponent();
        }

        private void MouseMoveTimer_Tick(object sender, EventArgs e)
        {
            Point cursor = new Point();
            GetCursorPos(ref cursor);

            var c = GetColorAt(cursor);
            this.BackColor = c;

            if (c.R == c.G && c.G < 64 && c.B > 128)
            {
                MessageBox.Show("Blue");
            }
        }

        Bitmap screenPixel = new Bitmap(1, 1, PixelFormat.Format32bppArgb);
        public Color GetColorAt(Point location)
        {
            // Create off-screen bitmaps for capturing screen pixels
            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 the captured pixel color
            return screenPixel.GetPixel(0, 0);
        }
    }
}

Polling for Pixel Color Change:

To continuously monitor a specific pixel color, you can utilize the following function within a loop or thread:

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

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

        Thread.Sleep();
    }
}

Conclusion:

This approach allows for accurate screen pixel color detection and enables reliable event triggering based on the color.

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