c picturebox 图像拖拽和缩放

核心步骤：

①新建Point类型全局变量mouseDownPoint，记录拖拽过程中鼠标位置；

②MouseDown事件记录Cursor位置；

③MouseMove事件计算移动矢量，并更新pictureBox1.Location。

代码：

private void pictureBox1_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { mouseDownPoint.X = Cursor.Position.X; //记录鼠标左键按下时位置 mouseDownPoint.Y = Cursor.Position.Y; isMove = true; pictureBox1.Focus(); //鼠标滚轮事件(缩放时)需要picturebox有焦点  } } private void pictureBox1_MouseUp(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { isMove = false; } } private void pictureBox1_MouseMove(object sender, MouseEventArgs e) { pictureBox1.Focus(); //鼠标在picturebox上时才有焦点，此时可以缩放 if (isMove) { int x, y; //新的pictureBox1.Location(x,y) int moveX, moveY; //X方向，Y方向移动大小。 moveX = Cursor.Position.X - mouseDownPoint.X; moveY = Cursor.Position.Y - mouseDownPoint.Y; x = pictureBox1.Location.X + moveX; y = pictureBox1.Location.Y + moveY; pictureBox1.Location = new Point(x, y); mouseDownPoint.X = Cursor.Position.X; mouseDownPoint.Y = Cursor.Position.Y; } } private void panel2_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { mouseDownPoint.X = Cursor.Position.X; //记录鼠标左键按下时位置 mouseDownPoint.Y = Cursor.Position.Y; isMove = true; } } private void panel2_MouseUp(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { isMove = false; } } private void panel2_MouseMove(object sender, MouseEventArgs e) { panel2.Focus(); //鼠标不在picturebox上时焦点给别的控件，此时无法缩放  if (isMove) { int x, y; //新的pictureBox1.Location(x,y) int moveX, moveY; //X方向，Y方向移动大小。 moveX = Cursor.Position.X - mouseDownPoint.X; moveY = Cursor.Position.Y - mouseDownPoint.Y; x = pictureBox1.Location.X + moveX; y = pictureBox1.Location.Y + moveY; pictureBox1.Location = new Point(x, y); mouseDownPoint.X = Cursor.Position.X; mouseDownPoint.Y = Cursor.Position.Y; } }

2.图像缩放

核心思想：利用picturebox的zoom模式，根据图像显示大小更改picturebox大小，记录鼠标位置补偿缩放位移，实现锚点缩放，即以鼠标位置为中心进行缩放。

zoomstep — 自己定义滚轮滑动缩放大小

代码：

//实现锚点缩放(以鼠标所指位置为中心缩放)； //步骤： //①先改picturebox长宽，长宽改变量一样； //②获取缩放后picturebox中实际显示图像的长宽，这里长宽是不一样的； //③将picturebox的长宽设置为显示图像的长宽； //④补偿picturebox因缩放产生的位移，实现锚点缩放。 // 注释：为啥要②③步？由于zoom模式的机制，把picturebox背景设为黑就知道为啥了。 //这里需要获取zoom模式下picturebox所显示图像的大小信息，添加 using System.Reflection； //pictureBox1_MouseWheel事件没找到。。。手动添加，别忘在Form1.Designer.cs的“Windows 窗体设计器生成的代码”里加入： //this.pictureBox1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseWheel)。 private void pictureBox1_MouseWheel(object sender, MouseEventArgs e) { int x = e.Location.X; int y = e.Location.Y; int ow = pictureBox1.Width; int oh = pictureBox1.Height; int VX, VY; //因缩放产生的位移矢量 if (e.Delta > 0) //放大  { //第①步 pictureBox1.Width += zoomStep;

 pictureBox1.Height += zoomStep; //第②步 PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance | BindingFlags.NonPublic); Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null); //第③步 pictureBox1.Width = rect.Width; pictureBox1.Height = rect.Height; } if (e.Delta < 0) //缩小  { //防止一直缩成负值 if (pictureBox1.Width < myBmp.Width / 10) return; pictureBox1.Width -= zoomStep; pictureBox1.Height -= zoomStep; PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance | BindingFlags.NonPublic); Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null); pictureBox1.Width = rect.Width; pictureBox1.Height = rect.Height; } //第④步，求因缩放产生的位移，进行补偿，实现锚点缩放的效果 VX = (int)((double)x * (ow - pictureBox1.Width) / ow); VY = (int)((double)y * (oh - pictureBox1.Height) / oh); pictureBox1.Location = new Point(pictureBox1.Location.X + VX, pictureBox1.Location.Y + VY); }