C#控件picturebox实现图像拖拽和缩放

本文实例为大家分享了c# picturebox实现图像拖拽和缩放的具体代码，供大家参考，具体内容如下

1.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);
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。