c# - 如何在 PictureBox 中平移图像

Question

我有一个自定义的 PictureBox，它可以使用 MouseWheel 事件进行放大。现在我想给它添加一个平移功能。我的意思是，当 PictureBox 处于缩放状态时，如果用户左键单击并按住单击然后移动鼠标，图像将在 picturebox 内平移。

这是我的代码，但不幸的是它不起作用!我不知道该去哪里找了...

private Point _panStartingPoint = Point.Empty;
private bool _panIsActive;

private void CurveBox_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        Focus();
        _panIsActive = true;
        _panStartingPoint = e.Location;
    }
}

private void CurveBox_MouseUp(object sender, MouseEventArgs e)
{
    _panIsActive = false;
}

private void CurveBox_MouseLeave(object sender, EventArgs e)
{
    _panIsActive = false;

}

private void CurveBox_MouseMove(object sender, MouseEventArgs e)
{
    if(_panIsActive && IsZoomed)
    {
        var g = CreateGraphics(); //Create graphics from PictureBox

        var nx = _panStartingPoint.X + e.X;
        var ny = _panStartingPoint.Y + e.Y;
        var sourceRectangle = new Rectangle(nx, ny, Image.Width, Image.Height);
        g.DrawImage(Image, nx, ny, sourceRectangle, GraphicsUnit.Pixel);
    }
}

我怀疑 MouseMove 事件...我不确定此事件和/或 nx 和 ny 是否发生任何事情包含正确的点。

非常感谢任何帮助/提示!

Answer 1

我认为数学是倒退的。像这样尝试:

private Point startingPoint = Point.Empty;
private Point movingPoint = Point.Empty;
private bool panning = false;

void pictureBox1_MouseDown(object sender, MouseEventArgs e) {
  panning = true;
  startingPoint = new Point(e.Location.X - movingPoint.X,
                            e.Location.Y - movingPoint.Y);
}

void pictureBox1_MouseUp(object sender, MouseEventArgs e) {
  panning = false;
}

void pictureBox1_MouseMove(object sender, MouseEventArgs e) {
  if (panning) {
    movingPoint = new Point(e.Location.X - startingPoint.X, 
                            e.Location.Y - startingPoint.Y);
    pictureBox1.Invalidate();
  }
}

void pictureBox1_Paint(object sender, PaintEventArgs e) {
  e.Graphics.Clear(Color.White);
  e.Graphics.DrawImage(Image, movingPoint);
}

您没有处理图形对象，CreateGraphics 只是一个临时绘图(最小化会删除它)所以我将绘图代码移到了 Paint 事件中，并且在用户平移时无效。