详解C#如何实现屏幕放大和取色功能

实践过程

效果

代码

public partial class Form1 : Form
{
   public Form1()
   {
       InitializeComponent();
   }

#region 定义快捷键
   //如果函数执行成功，返回值不为0。      
   //如果函数执行失败，返回值为0。要得到扩展错误信息，调用GetLastError。        
   [DllImport("user32.dll", SetLastError = true)]
   public static extern bool RegisterHotKey(
   IntPtr hWnd,                //要定义热键的窗口的句柄            
   int id,                     //定义热键ID（不能与其它ID重复）                      
   KeyModifiers fsModifiers,   //标识热键是否在按Alt、Ctrl、Shift、Windows等键时才会生效        
   Keys vk                     //定义热键的内容            
);
   [DllImport("user32.dll", SetLastError = true)]
   public static extern bool UnregisterHotKey(
       IntPtr hWnd,                //要取消热键的窗口的句柄            
       int id                      //要取消热键的ID            
   );
   //定义了辅助键的名称（将数字转变为字符以便于记忆，也可去除此枚举而直接使用数值）        
   [Flags()]
   public enum KeyModifiers
   {
       None = 0,
       Alt = 1,
       Ctrl = 2,
       Shift = 4,
       WindowsKey = 8
   }
   #endregion

#region 获取鼠标像素的RGB
   [DllImport("gdi32.dll")]
   static public extern uint GetPixel(IntPtr hDC, int XPos, int YPos);
   [DllImport("gdi32.dll")]
   static public extern IntPtr CreateDC(string driverName, string deviceName, string output, IntPtr lpinitData);
   [DllImport("gdi32.dll")]
   static public extern bool DeleteDC(IntPtr DC);
   static public byte GetRValue(uint color)
   {
       return (byte)color;
   }
   static public byte GetGValue(uint color)
   {
       return ((byte)(((short)(color)) >> 8));
   }
   static public byte GetBValue(uint color)
   {
       return ((byte)((color) >> 16));
   }
   static public byte GetAValue(uint color)
   {
       return ((byte)((color) >> 24));
   }
   public Color GetColor(Point screenPoint)
   {
       IntPtr displayDC = CreateDC("DISPLAY", null, null, IntPtr.Zero);
       uint colorref = GetPixel(displayDC, screenPoint.X, screenPoint.Y);
       DeleteDC(displayDC);
       byte Red = GetRValue(colorref);
       byte Green = GetGValue(colorref);
       byte Blue = GetBValue(colorref);
       return Color.FromArgb(Red, Green, Blue);
   }
   #endregion

int screenWidth;        //屏幕宽度
   int screenHeight;       //屏幕高度
   int mx;                 //鼠标x坐标
   int my;                 //鼠标y坐标
   const int imgWidth = 234;//放大后图片的宽度
   const int imgHeight = 134;//放大后图片的高度

private void Form1_Load(object sender, EventArgs e)
   {
       this.Location = new Point(0,0);
       screenWidth = Screen.PrimaryScreen.WorkingArea.Width;
       screenHeight = Screen.PrimaryScreen.WorkingArea.Height;
       this.TopMost = true;
   }

private void timer1_Tick(object sender, EventArgs e)
   {
       RegisterHotKey(Handle, 81, KeyModifiers.None, Keys.Escape);
       mx = Control.MousePosition.X;
       my = Control.MousePosition.Y;
       lblmPos.Text="("+mx.ToString()+","+my.ToString()+")";
       Point pt = new Point(mx,my);
       Color cl = GetColor(pt);
       lblRGB.Text = "(" + cl.R.ToString() + "," + cl.G.ToString() + "," + cl.B + ")";
       if (mx <= this.Width&&my<=this.Height)
       {
           this.Location = new Point(screenWidth-this.Width,0);
       }
       if (mx >= screenWidth - this.Width&&my<=this.Height)
       {
           this.Location = new Point(0,0);
       }
       Bitmap bt = new Bitmap(imgWidth/2,imgHeight/2);
       Graphics g = Graphics.FromImage(bt);
       g.CopyFromScreen(new Point(Cursor.Position.X-imgWidth/4,Cursor.Position.Y-imgHeight/4),new Point(0,0),new Size(imgWidth/2,imgHeight/2));
       IntPtr dc1 = g.GetHdc();
       g.ReleaseHdc(dc1);
       pictureBox1.Image = (Image)bt;

}

protected override void WndProc(ref Message m)
   {
       const int WM_HOTKEY = 0x0312;
       //按快捷键    
       switch (m.Msg)
       {
           case WM_HOTKEY:
               switch (m.WParam.ToInt32())
               {
                   case 81:    //按下的是ESC    
                       Application.Exit();
                       break;
               }
               break;
       }
       base.WndProc(ref m);
   }

private void Form1_FormClosed(object sender, FormClosedEventArgs e)
   {
       //注销Id号为81的热键设定    
       UnregisterHotKey(Handle, 81);
   }

private void pictureBox1_Paint(object sender, PaintEventArgs e)
   {
       Graphics g = e.Graphics;
       g.DrawLine(new Pen(Color.Red), new PointF(pictureBox1.Width / 2, 0), new PointF(pictureBox1.Width / 2,pictureBox1.Height));
       g.DrawLine(new Pen(Color.Red,2), new PointF(0, pictureBox1.Height / 2), new PointF(pictureBox1.Width, pictureBox1.Height/2));
   }
}

partial class Form1
   {
       /// <summary>
       /// 必需的设计器变量。
       /// </summary>
       private System.ComponentModel.IContainer components = null;

/// <summary>
       /// 清理所有正在使用的资源。
       /// </summary>
       /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>
       protected override void Dispose(bool disposing)
       {
           if (disposing && (components != null))
           {
               components.Dispose();
           }
           base.Dispose(disposing);
       }

#region Windows 窗体设计器生成的代码

/// <summary>
       /// 设计器支持所需的方法 - 不要
       /// 使用代码编辑器修改此方法的内容。
       /// </summary>
       private void InitializeComponent()
       {
           this.components = new System.ComponentModel.Container();
           this.timer1 = new System.Windows.Forms.Timer(this.components);
           this.label2 = new System.Windows.Forms.Label();
           this.lblmPos = new System.Windows.Forms.Label();
           this.label3 = new System.Windows.Forms.Label();
           this.label4 = new System.Windows.Forms.Label();
           this.lblRGB = new System.Windows.Forms.Label();
           this.pictureBox1 = new System.Windows.Forms.PictureBox();
           ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
           this.SuspendLayout();
           //
           // timer1
           //
           this.timer1.Enabled = true;
           this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
           //
           // label2
           //
           this.label2.AutoSize = true;
           this.label2.BackColor = System.Drawing.Color.Transparent;
           this.label2.ForeColor = System.Drawing.Color.Black;
           this.label2.Location = new System.Drawing.Point(12, 122);
           this.label2.Name = "label2";
           this.label2.Size = new System.Drawing.Size(65, 12);
           this.label2.TabIndex = 2;
           this.label2.Text = "鼠标位置：";
           //
           // lblmPos
           //
           this.lblmPos.AutoSize = true;
           this.lblmPos.BackColor = System.Drawing.Color.Transparent;
           this.lblmPos.ForeColor = System.Drawing.Color.Black;
           this.lblmPos.Location = new System.Drawing.Point(83, 122);
           this.lblmPos.Name = "lblmPos";
           this.lblmPos.Size = new System.Drawing.Size(41, 12);
           this.lblmPos.TabIndex = 3;
           this.lblmPos.Text = "label3";
           //
           // label3
           //
           this.label3.AutoSize = true;
           this.label3.BackColor = System.Drawing.Color.Transparent;
           this.label3.ForeColor = System.Drawing.Color.Black;
           this.label3.Location = new System.Drawing.Point(10, 47);
           this.label3.Name = "label3";
           this.label3.Size = new System.Drawing.Size(125, 12);
           this.label3.TabIndex = 5;
           this.label3.Text = "⊙ 当前像素的RGB值：";
           //
           // label4
           //
           this.label4.AutoSize = true;
           this.label4.BackColor = System.Drawing.Color.Transparent;
           this.label4.ForeColor = System.Drawing.Color.Black;
           this.label4.Location = new System.Drawing.Point(10, 73);
           this.label4.Name = "label4";
           this.label4.Size = new System.Drawing.Size(125, 12);
           this.label4.TabIndex = 6;
           this.label4.Text = "⊙ 按ESC键关闭放大镜";
           //
           // lblRGB
           //
           this.lblRGB.AutoSize = true;
           this.lblRGB.BackColor = System.Drawing.Color.Transparent;
           this.lblRGB.ForeColor = System.Drawing.Color.Black;
           this.lblRGB.Location = new System.Drawing.Point(129, 47);
           this.lblRGB.Name = "lblRGB";
           this.lblRGB.Size = new System.Drawing.Size(41, 12);
           this.lblRGB.TabIndex = 7;
           this.lblRGB.Text = "label5";
           //
           // pictureBox1
           //
           this.pictureBox1.BackColor = System.Drawing.Color.White;
           this.pictureBox1.Location = new System.Drawing.Point(3, 146);
           this.pictureBox1.Name = "pictureBox1";
           this.pictureBox1.Size = new System.Drawing.Size(234, 134);
           this.pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.Zoom;
           this.pictureBox1.TabIndex = 8;
           this.pictureBox1.TabStop = false;
           this.pictureBox1.Paint += new System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);
           //
           // Form1
           //
           this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
           this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
           this.BackgroundImage = global::ScreenBlowupGlass.Properties.Resources.bg;
           this.ClientSize = new System.Drawing.Size(241, 284);
           this.Controls.Add(this.pictureBox1);
           this.Controls.Add(this.lblRGB);
           this.Controls.Add(this.label4);
           this.Controls.Add(this.label3);
           this.Controls.Add(this.lblmPos);
           this.Controls.Add(this.label2);
           this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
           this.MaximizeBox = false;
           this.MinimizeBox = false;
           this.Name = "Form1";
           this.Text = "屏幕放大镜";
           this.Load += new System.EventHandler(this.Form1_Load);
           this.FormClosed += new System.Windows.Forms.FormClosedEventHandler(this.Form1_FormClosed);
           ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
           this.ResumeLayout(false);
           this.PerformLayout();

}

#endregion

private System.Windows.Forms.Timer timer1;
       private System.Windows.Forms.Label label2;
       private System.Windows.Forms.Label lblmPos;
       private System.Windows.Forms.Label label3;
       private System.Windows.Forms.Label label4;
       private System.Windows.Forms.Label lblRGB;
       private System.Windows.Forms.PictureBox pictureBox1;
   }

来源：https://blog.csdn.net/qq_27489007/article/details/128305999