在 C# 和 WPF 中选择屏幕截图不准确

Question

我制作了一个程序，用于从屏幕上的选定区域拍摄屏幕截图，但它不准确，我不知道为什么。这可能是因为鼠标坐标，但我不知道我做错了什么。也许你们中的一些人可以弄清楚。屏幕截图始终处于关闭状态，它会捕获实际选择上方的屏幕区域，因此会“剪切”选择的下部。这是我的代码：

     public  partial class Selektiranje : Window
    {
        public double x;
        public double y;
        public double width;
        public double height;
        public bool isMouseDown = false;


        public Selektiranje()
        {
            InitializeComponent();
        }

       private void Window_MouseDown(object sender, MouseButtonEventArgs e) 
        {
            isMouseDown = true;
            x = e.GetPosition(null).X;                                                  //Selekcija Screenshota
            y = e.GetPosition(null).Y;
        }

        public  void Window_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            if (this.isMouseDown)
            {
                double curx = e.GetPosition(null).X;
                double cury = e.GetPosition(null).Y;

                System.Windows.Shapes.Rectangle r = new  , System.Windows.Shapes.Rectangle();
                SolidColorBrush brush = new SolidColorBrush(Colors.White);
                r.Stroke = brush;
                r.Fill = brush;
                r.StrokeThickness = 1;
                r.Width = Math.Abs(curx - x);
                r.Height = Math.Abs(cury - y);
                selekt.Children.Clear();
                selekt.Children.Add(r);
                Canvas.SetLeft(r, x);
                Canvas.SetTop(r, y);
                if (e.LeftButton == MouseButtonState.Released)
                {
                    selekt.Children.Clear();
                    width = e.GetPosition(null).X - x;
                    height = e.GetPosition(null).Y - y;
                    this.CaptureScreen(x, y, width, height);
                    this.x = this.y = 0;
                    this.isMouseDown = false;
                    this.Close();
                }
            }
        }
        public void CaptureScreen(double x, double y, double width, double height)
        {
            int ix, iy, iw, ih;
            ix = Convert.ToInt32(x);
            iy = Convert.ToInt32(y);
            iw = Convert.ToInt32(width);
            ih = Convert.ToInt32(height);
            Bitmap slika = new Bitmap(iw, ih,       System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            Graphics g = Graphics.FromImage(slika);
            g.CopyFromScreen(ix, iy, 0, 0,new System.Drawing.Size(iw, ih),CopyPixelOperation.SourceCopy);


 public void SaveScreen(double x, double y, double width, double height)
        {
            int ix, iy, iw, ih;
            ix = Convert.ToInt32(x);
            iy = Convert.ToInt32(y);
            iw = Convert.ToInt32(width);
            ih = Convert.ToInt32(height);
            try
            {
                Bitmap slika = new Bitmap(iw, ih);
                Graphics gr1 = Graphics.FromImage(slika);
                IntPtr dc1 = gr1.GetHdc();
                IntPtr dc2 = NativeMethods.GetWindowDC(NativeMethods.GetForegroundWindow());
                NativeMethods.BitBlt(dc1, ix, iy, iw, ih, dc2, ix, iy, 13369376);
                gr1.ReleaseHdc(dc1);
                System.Windows.Forms.SaveFileDialog dlg = new System.Windows.Forms.SaveFileDialog();
                dlg.DefaultExt = "png";
                dlg.Filter = "Png Files|*.png";
                DialogResult res = dlg.ShowDialog();
                if (res == System.Windows.Forms.DialogResult.OK)
                    slika.Save(dlg.FileName, ImageFormat.Png);

            }
            catch 
            {

            }

        }
        internal class NativeMethods
        {

            [DllImport("user32.dll")]
            public extern static IntPtr GetDesktopWindow();
            [DllImport("user32.dll")]
            public static extern IntPtr GetWindowDC(IntPtr hwnd);
            [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern IntPtr GetForegroundWindow();
        [DllImport("gdi32.dll")]
        public static extern UInt64 BitBlt(IntPtr hDestDC, int x, int y, int nWidth, int nHeight, IntPtr hSrcDC, int xSrc, int ySrc, System.Int32 dwRop);

    }

}

}

Answer 1

Window_MouseDown() 和 Window_MouseMove() 中需要 Cursor.Position (MSDN)，它返回绝对鼠标坐标。

   private void Window_MouseDown(object sender, MouseButtonEventArgs e) 
    {
        isMouseDown = true;
        x = Cursor.Position.X;
        y = Cursor.Position.Y;
    }

下面的完整工作解决方案的代码（对我而言）。我删除了不必要的代码，例如绘制矩形。另外，我在截屏之前隐藏了表单。您还可以将表单的背景颜色设置为特定值，并将透明度键设置为相同的值或其他内容。

但基本概念仍然存在：使用绝对屏幕坐标。

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Controls;
using System.Windows.Forms;
using System.Windows.Media;
using PixelFormat = System.Drawing.Imaging.PixelFormat;
using Rectangle = System.Windows.Shapes.Rectangle;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public double x;
        public double y;
        public double width;
        public double height;
        public bool isMouseDown;

        public Form1()
        {
            InitializeComponent();
        }

        public void SaveScreen(double x, double y, double width, double height)
        {
            var ix = Convert.ToInt32(x);
            var iy = Convert.ToInt32(y);
            var iw = Convert.ToInt32(width);
            var ih = Convert.ToInt32(height);
            try
            {
                var slika = new Bitmap(iw, ih, PixelFormat.Format32bppArgb);
                var g = Graphics.FromImage(slika);
                g.CopyFromScreen(ix, iy, 0, 0, new Size(iw, ih), CopyPixelOperation.SourceCopy);

                var dlg = new SaveFileDialog
                {
                    DefaultExt = "png",
                    Filter = "Png Files|*.png"
                };
                var res = dlg.ShowDialog();
                if (res == DialogResult.OK) slika.Save(dlg.FileName, ImageFormat.Png);
            }
            catch
            {
            }

        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            isMouseDown = true;
            x = Cursor.Position.X;
            y = Cursor.Position.Y;
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {

        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            width = Cursor.Position.X - x;
            height = Cursor.Position.Y - y;
            Hide();
            Size = new Size(0, 0);
            Application.DoEvents();
            SaveScreen(x, y, width, height);
            x = y = 0;
            isMouseDown = false;
            Close();
        }

    }
}

Answer 2

Graphics.CopyFromScreen需要屏幕坐标拍照。由于使用了MouseEventArgs 的 e.x 和 e.y，您正在传递相对于表单的坐标。您应该改用鼠标的屏幕坐标，使用相同的Cursor.Position 或MousePosition。

如果您使用的是 WPF

有许多选项可以帮助您获取屏幕坐标，其中一些选项：

选项 1

您可以使用PointToScreen方法将坐标转换为屏幕坐标。

选项 2

在 WPF 中你不能使用这些方法，最简单的方法是在你的 WPF 项目中添加对System.Windows.Forms.dll 的引用，然后使用静态的System.Windows.Forms.Control.MousePosition。

选项 3

作为另一种选择，您可以添加对System.Drawing.dll 的引用并使用它：

[System.Runtime.InteropServices.DllImport("user32.dll")]
[return: System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.Bool)]
internal static extern bool GetCursorPos(ref PointStruct point);

[System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)]
internal struct PointStruct
{
    public Int32 X;
    public Int32 Y;
};

public static System.Drawing.Point MousePosition()
{
    var mousePosition = new PointStruct();
    GetCursorPos(ref mousePosition);
    return new System.Drawing.Point(mousePosition.X, mousePosition.Y);
}

然后你可以使用MousePosition()来获取鼠标在屏幕上的当前位置。