C#图像显示实现拖拽、锚点缩放功能[转有耐心的小王]

1.图像拖拽

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：

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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;
}
}

来自CODE的代码片

picmove.cs

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。

代码：

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//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);
}