Как найти пиксель нужного цвета с

asked Sep 27, 2009 at 16:51

This is the most efficient: It grabs a pixel at the location of the cursor, and doesn’t rely on only having one monitor.

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

namespace FormTest
{
    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)
        {
            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);
        }
    }
}

Now, obviously, you don’t have to use the cursor’s current location, but this is the general idea.

EDIT:

Given the above GetColorAt function you can poll a certain pixel on the screen in a safe, performance friendly way like this:

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;
        }

        // By calling Thread.Sleep() without a parameter, we are signaling to the
        // operating system that we only want to sleep long enough for other
        // applications.  As soon as the other apps yield their CPU time, we will
        // regain control.
        Thread.Sleep()
    }
}

You can wrap that in a Thread if you want, or execute it from a Console application. «Whatever suits your fancy,» I guess.

answered Sep 27, 2009 at 17:05

Most answers here use the very same source of that pixel (desktop dc).
The key function is GetPixel.

[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr GetWindowDC(IntPtr window);
[DllImport("gdi32.dll", SetLastError = true)]
public static extern uint GetPixel(IntPtr dc, int x, int y);
[DllImport("user32.dll", SetLastError = true)]
public static extern int ReleaseDC(IntPtr window, IntPtr dc);

public static Color GetColorAt(int x, int y)
{
    IntPtr desk = GetDesktopWindow();
    IntPtr dc = GetWindowDC(desk);
    int a = (int) GetPixel(dc, x, y);
    ReleaseDC(desk, dc);
    return Color.FromArgb(255, (a >> 0) & 0xff, (a >> 8) & 0xff, (a >> 16) & 0xff);
}

I think this is the cleanest and quickest way.

Note:

If you have modified the default text size among the Display Settings on Windows to increase readability on a high resolution display, the coordinate parameters of GetPixel() need to be adjusted the same way. For example, if the cursor location is (x,y) with 150% of text size on Windows 7, you need to call GetPixel(x*1.5, y*1.5) to get the color of the pixel under the cursor.

answered Jul 15, 2014 at 13:23

This function is shorter and can achieve the same result using System.Drawing, without Pinvoke.

Color GetColorAt(int x, int y)
{
    Bitmap bmp = new Bitmap(1, 1);
    Rectangle bounds = new Rectangle(x, y, 1, 1);
    using (Graphics g = Graphics.FromImage(bmp))
        g.CopyFromScreen(bounds.Location, Point.Empty, bounds.Size);
    return bmp.GetPixel(0, 0);
}

MRGMRG

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As far as I know the easiest way to do this is to:

1. take a screenshot
2. look at the bitmap and get the pixel color

Edit

There is probably no way to «wait» until the pixel changes to a certain color. Your program will probably have to just loop and check it every so often until it sees the color.

For example:

while(!IsPixelColor(x, y, color))
{
    //probably best to add a sleep here so your program doesn't use too much CPU
}
DoAction();

EDIT 2

Here is some sample code you can modify. This code just changes the color of a label based on the current color in a given pixel. This code avoids the handle leak mentioned.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{

    [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);


    Thread t;
    int x, y;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        x = 20;
        y = 50;
        t = new Thread(update);
        t.Start();
    }

    private void update()
    {
        Bitmap screenCopy = new Bitmap(1, 1);
        using (Graphics gdest = Graphics.FromImage(screenCopy))
        {
            while (true)
            {
                //g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(256, 256));
                using (Graphics gsrc = Graphics.FromHwnd(IntPtr.Zero))
                {
                    IntPtr hSrcDC = gsrc.GetHdc();
                    IntPtr hDC = gdest.GetHdc();
                    int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, x, y, (int)CopyPixelOperation.SourceCopy);
                    gdest.ReleaseHdc();
                    gsrc.ReleaseHdc();
                }
                Color c = Color.FromArgb(screenCopy.GetPixel(0, 0).ToArgb());
                label1.ForeColor = c;
            }
        }
    }
}

}

answered Sep 27, 2009 at 16:56