C# 实现QQ式截图功能

这个功能一共有两部分组成,第一部分是窗体代码，另外的一部分是一个辅助方法。直接贴出代码，以供大家参考：

 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.Drawing.Drawing2D;
 using System.Drawing.Imaging;
 using ImageClassLib;
 namespace ImageShear
 {
     public partial class Demo: Form
     {
         public Demo()
         {
             InitializeComponent();
         }
         #region 点击打开图像
         public string strHeadImagePath; //打开图片的路径
         Bitmap Bi;  //定义位图对像
         private void button1_Click(object sender, EventArgs e)
         {
             openFileDialog1.Filter = "*.gif|*.jpg|*.JPEG|*.JPEG|*.bmp|*.bmp";         //设置读取图片类型
             if (openFileDialog1.ShowDialog() == DialogResult.OK)
             {
                 try
                 {
                     strHeadImagePath = openFileDialog1.FileName;
                     //this.Show(strHeadImagePath);
                     Bi = new Bitmap(strHeadImagePath);  //使用打开的图片路径创建位图对像
                     ImageCut1 IC = new ImageCut1(, , this.pictureBox1.Width, this.pictureBox1.Height);      //实例化ImageCut类，四个参数据分别表示为：x、y、width、heigth，（40、112）表示pictureBox1的Lcation的坐标，（120、144）表示pictureBox1控件的宽度和高度
                     this.pictureBox1.Image = IC.KiCut1((Bitmap)(this.GetSelectImage(this.pictureBox1.Width, this.pictureBox1.Height)));     //（120、144）表示pictureBox1控件的宽度和高度
                     //this.pictureBox1.Image = (this.GetSelectImage(120, 144));
                 }
                 catch (Exception ex)
                 {
                     MessageBox.Show("格式不对");
                     ex.ToString();
                 }
             }
         }
         #endregion
         #region 定义显示图像方法，即将打开的图像在pictureBox1控件显示
         public void Show(string strHeadImagePath)
         {
             this.pictureBox1.Load(@strHeadImagePath);   //
         }
         #endregion
         #region 获取图像
         /// <summary>
         /// 获取指定宽度和高度的图像即使图片和pictureBox1控件一样宽和高，返回值为图片Image
         /// </summary>
         /// <param name="Width表示宽"></param>
         /// <param name="Height表示高"></param>
         /// <returns></returns>
         public Image GetSelectImage(int Width, int Height)
         {
             //Image initImage = this.pictureBox1.Image;
             Image initImage = Bi;
             //原图宽高均小于模版，不作处理，直接保存
             if (initImage.Width <= Width && initImage.Height <= Height)
             {
                 //initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
                 return initImage;
             }
             else
             {
                 //原始图片的宽、高
                 int initWidth = initImage.Width;
                 int initHeight = initImage.Height;

                 //非正方型先裁剪为正方型
                 if (initWidth != initHeight)
                 {
                     //截图对象
                     System.Drawing.Image pickedImage = null;
                     System.Drawing.Graphics pickedG = null;

                     //宽大于高的横图
                     if (initWidth > initHeight)
                     {
                         //对象实例化
                         pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);
                         pickedG = System.Drawing.Graphics.FromImage(pickedImage);
                         //设置质量
                         pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                         pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                         //定位
                         Rectangle fromR = new Rectangle((initWidth - initHeight) / , , initHeight, initHeight);
                         Rectangle toR = new Rectangle(, , initHeight, initHeight);
                         //画图
                         pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
                         //重置宽
                         initWidth = initHeight;
                     }
                     //高大于宽的竖图
                     else
                     {
                         //对象实例化
                         pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);
                         pickedG = System.Drawing.Graphics.FromImage(pickedImage);
                         //设置质量
                         pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                         pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                         //定位
                         Rectangle fromR = new Rectangle(, (initHeight - initWidth) / , initWidth, initWidth);
                         Rectangle toR = new Rectangle(, , initWidth, initWidth);
                         //画图
                         pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
                         //重置高
                         initHeight = initWidth;
                     }

                     initImage = (System.Drawing.Image)pickedImage.Clone();
                     //                //释放截图资源
                     pickedG.Dispose();
                     pickedImage.Dispose();
                 }

                 return initImage;
             }
         }
         #endregion
         #region 点击button2按钮事件
         private void button2_Click(object sender, EventArgs e)
         {
             this.label1.Text = "裁剪后的图片宽度："+this.pictureBox2.Width.ToString();
             this.label2.Text = "裁剪后的图片高度："+this.pictureBox2.Height.ToString();
         }
         #endregion
         #region 缩放、裁剪图像用到的变量
         /// <summary>
         ///
         /// </summary>
         int x1;     //鼠标按下时横坐标
         int y1;     //鼠标按下时纵坐标
         int width;  //所打开的图像的宽
         int heigth; //所打开的图像的高
         bool HeadImageBool = false;    // 此布尔变量用来判断pictureBox1控件是否有图片
         #endregion
         #region 画矩形使用到的变量
         Point p1;   //定义鼠标按下时的坐标点
         Point p2;   //定义移动鼠标时的坐标点
         Point p3;   //定义松开鼠标时的坐标点
         #endregion
         #region 鼠标按下时发生的事件
         private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
         {
             this.Cursor = Cursors.Cross;
             this.p1 = new Point(e.X, e.Y);
             x1 = e.X;
             y1 = e.Y;
             if (this.pictureBox1.Image != null)
             {
                 HeadImageBool = true;
             }
             else
             {
                 HeadImageBool = false;
             }
         }
         #endregion
         #region 移动鼠标发生的事件
         private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
         {
             if (this.Cursor == Cursors.Cross)
             {
                 this.p2 = new Point(e.X, e.Y);
                 if ((p2.X - p1.X) >  && (p2.Y - p1.Y) > )     //当鼠标从左上角向开始移动时P3坐标
                 {
                     this.p3 = new Point(p1.X, p1.Y);
                 }
                 if ((p2.X - p1.X) <  && (p2.Y - p1.Y) > )     //当鼠标从右上角向左下方向开始移动时P3坐标
                 {
                     this.p3 = new Point(p2.X, p1.Y);
                 }
                 if ((p2.X - p1.X) >  && (p2.Y - p1.Y) < )     //当鼠标从左下角向上开始移动时P3坐标
                 {
                     this.p3 = new Point(p1.X, p2.Y);
                 }
                 if ((p2.X - p1.X) <  && (p2.Y - p1.Y) < )     //当鼠标从右下角向左方向上开始移动时P3坐标
                 {
                     this.p3 = new Point(p2.X, p2.Y);
                 }
                 this.pictureBox1.Invalidate();  //使控件的整个图面无效，并导致重绘控件
             }
         }
         #endregion
         #region 松开鼠标发生的事件，实例化ImageCut1类对像
         ImageCut1 IC1;  //定义所画矩形的图像对像
         private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
         {
             if (HeadImageBool)
             {
                 width = this.pictureBox1.Image.Width;
                 heigth = this.pictureBox1.Image.Height;
                 if ((e.X - x1) >  && (e.Y - y1) > )   //当鼠标从左上角向右下方向开始移动时发生
                 {
                     IC1 = new ImageCut1(x1, y1, Math.Abs(e.X - x1), Math.Abs(e.Y - y1));    //实例化ImageCut1类
                 }
                 if ((e.X - x1) <  && (e.Y - y1) > )   //当鼠标从右上角向左下方向开始移动时发生
                 {
                     IC1 = new ImageCut1(e.X, y1, Math.Abs(e.X - x1), Math.Abs(e.Y - y1));   //实例化ImageCut1类
                 }
                 if ((e.X - x1) >  && (e.Y - y1) < )   //当鼠标从左下角向右上方向开始移动时发生
                 {
                     IC1 = new ImageCut1(x1, e.Y, Math.Abs(e.X - x1), Math.Abs(e.Y - y1));   //实例化ImageCut1类
                 }
                 if ((e.X - x1) <  && (e.Y - y1) < )   //当鼠标从右下角向左上方向开始移动时发生
                 {
                     IC1 = new ImageCut1(e.X, e.Y, Math.Abs(e.X - x1), Math.Abs(e.Y - y1));      //实例化ImageCut1类
                 }
                 this.pictureBox2.Width = (IC1.KiCut1((Bitmap)(this.pictureBox1.Image))).Width;
                 this.pictureBox2.Height = (IC1.KiCut1((Bitmap)(this.pictureBox1.Image))).Height;
                 this.pictureBox2.Image = IC1.KiCut1((Bitmap)(this.pictureBox1.Image));
                 this.Cursor = Cursors.Default;
             }
             else
             {
                 this.Cursor = Cursors.Default;
             }
         }
         #endregion
         #region 获取所选矩形图像
         /// <summary>
         ///
         /// </summary>
         /// <param name="Width"></param>
         /// <param name="Height"></param>
         /// <returns></returns>
         public Image GetSelectImage1(int Width, int Height)
         {
             Image initImage = this.pictureBox1.Image;
             //Image initImage = Bi;
             //原图宽高均小于模版，不作处理，直接保存
             if (initImage.Width <= Width && initImage.Height <= Height)
             {
                 //initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
                 return initImage;
             }
             else
             {
                 //原始图片的宽、高
                 int initWidth = initImage.Width;
                 int initHeight = initImage.Height;

                 //非正方型先裁剪为正方型
                 if (initWidth != initHeight)
                 {
                     //截图对象
                     System.Drawing.Image pickedImage = null;
                     System.Drawing.Graphics pickedG = null;

                     //宽大于高的横图
                     if (initWidth > initHeight)
                     {
                         //对象实例化
                         pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);
                         pickedG = System.Drawing.Graphics.FromImage(pickedImage);
                         //设置质量
                         pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                         pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                         //定位
                         Rectangle fromR = new Rectangle((initWidth - initHeight) / , , initHeight, initHeight);
                         Rectangle toR = new Rectangle(, , initHeight, initHeight);
                         //画图
                         pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
                         //重置宽
                         initWidth = initHeight;
                     }
                     //高大于宽的竖图
                     else
                     {
                         //对象实例化
                         pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);
                         pickedG = System.Drawing.Graphics.FromImage(pickedImage);
                         //设置质量
                         pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                         pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                         //定位
                         Rectangle fromR = new Rectangle(, (initHeight - initWidth) / , initWidth, initWidth);
                         Rectangle toR = new Rectangle(, , initWidth, initWidth);
                         //画图
                         pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
                         //重置高
                         initHeight = initWidth;
                     }

                     initImage = (System.Drawing.Image)pickedImage.Clone();
                     //                //释放截图资源
                     pickedG.Dispose();
                     pickedImage.Dispose();
                 }

                 return initImage;
             }
         }
         #endregion
         #region 重新绘制pictureBox1控件，即移动鼠标画矩形
         private void pictureBox1_Paint(object sender, PaintEventArgs e)
         {
             if (HeadImageBool)
             {
                 Pen p = new Pen(Color.Black, );//画笔
                 p.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
                 //Bitmap bitmap = new Bitmap(strHeadImagePath);
                 Bitmap bitmap = Bi;
                 Rectangle rect = new Rectangle(p3, new Size(System.Math.Abs(p2.X - p1.X), System.Math.Abs(p2.Y - p1.Y)));
                 e.Graphics.DrawRectangle(p, rect);
             }
             else
             {

             }
         }
         #endregion
     }
 }

第二部分是辅助方法类

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Drawing;
 using System.Drawing.Drawing2D;
 using System.Drawing.Imaging;
 namespace ImageClassLib
 {
     public class ImageCut1
     {
         #region 剪裁图片方法
         /// <summary>
         /// 剪裁 -- 用GDI+
         /// </summary>
         /// <param name="b">原始Bitmap,即需要裁剪的图片</param>
         /// <param name="StartX">开始坐标X</param>
         /// <param name="StartY">开始坐标Y</param>
         /// <param name="iWidth">宽度</param>
         /// <param name="iHeight">高度</param>
         /// <returns>剪裁后的Bitmap</returns>
         public Bitmap KiCut1(Bitmap b)
         {
             if (b == null)
             {
                 return null;
             } 

             int w = b.Width;
             int h = b.Height; 

             if (X >= w || Y >= h)
             {
                 return null;
             } 

             if (X + Width > w)
             {
                 Width = w - X;
             } 

             if (Y + Height > h)
             {
                 Height = h - Y;
             } 

             try
             {
                 Bitmap bmpOut = new Bitmap(Width, Height, PixelFormat.Format24bppRgb); 

                 Graphics g = Graphics.FromImage(bmpOut);
                 // Create rectangle for displaying image.
                 Rectangle destRect = new Rectangle(, , Width, Height);        //所画的矩形正确，它指定所绘制图像的位置和大小。 将图像进行缩放以适合该矩形。

                 // Create rectangle for source image.
                 Rectangle srcRect = new Rectangle(X, Y, Width, Height);      //srcRect参数指定要绘制的 image 对象的矩形部分。 将此部分进行缩放以适合 destRect 参数所指定的矩形。

                 g.DrawImage(b, destRect, srcRect, GraphicsUnit.Pixel);
                 //resultG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.GraphicsUnit.Pixel);
                 g.Dispose();
                 return bmpOut;
             }
             catch
             {
                 return null;
             }
         }
         #endregion
         #region ImageCut1类的构造函数
         public int X;
         public int Y;
         public int Width ;
         public int Height;
         /// <summary>
         /// ImageCut1类的构造函数，ImageCut1类用来获取鼠标在pictureBox1控件所画矩形内的图像
         /// </summary>
         /// <param name="x表示鼠标在pictureBox1控件上按下时的横坐标"></param>
         /// <param name="y表示鼠标在pictureBox1控件上按下时的纵坐标"></param>
         /// <param name="width表示鼠标在pictureBox1控件上松开鼠标的宽度"></param>
         /// <param name="heigth表示鼠标在pictureBox1控件上松开鼠标的高度"></param>
         public ImageCut1(int x, int y, int width, int heigth)
         {
             X = x;
             Y = y;
             Width = width;
             Height = heigth;
         }
         #endregion
     }
 }

实现的效果如下：