【C#/WPF】Image图片的Transform变换：平移、缩放、旋转

WPF中图像控件Image的变换属性Transform：

• 平移
• 缩放
• 旋转

即要想实现图片的平移、缩放、旋转，是修改它所在的Image控件的Transform变换属性。

下面在XAML中定义了Image图片的Transform属性。

<Image>
    <Image.RenderTransform>
        <TransformGroup>
            <TranslateTransform/>
            <ScaleTransform/>
            <RotateTransform/>
        </TransformGroup>
    </Image.RenderTransform>
</Image>

图像平移：

按住鼠标左键，拖拽移动图片；松开鼠标左键，完成图像平移。
MVVM将鼠标事件绑定命令Command后在控制层处理。

private Image movingObject;  // 记录当前被拖拽移动的图片
private Point StartPosition; // 本次移动开始时的坐标点位置
private Point EndPosition;   // 本次移动结束时的坐标点位置

/// <summary>
/// 按下鼠标左键，准备开始拖动图片
/// </summary>
/// <param name="p"></param>
private void MouseLeftButtonDownCommand(object[] p)
{
    object sender = p[0];
    MouseButtonEventArgs e = p[1] as MouseButtonEventArgs;
    Image img = sender as Image;

    movingObject = img;
    StartPosition = e.GetPosition(img);
}

/// <summary>
/// 按住鼠标左键，拖动图片平移
/// </summary>
/// <param name="p"></param>
private void MouseMoveCommand(object[] p)
{
    object sender = p[0];
    MouseEventArgs e = p[1] as MouseEventArgs;
    Image img = sender as Image;

    if (e.LeftButton == MouseButtonState.Pressed && sender == movingObject)
    {
        EndPosition = e.GetPosition(img);

        TransformGroup tg = img.RenderTransform as TransformGroup;
        var tgnew = tg.CloneCurrentValue();
        if (tgnew != null)
        {
            TranslateTransform tt = tgnew.Children[0] as TranslateTransform;

            var X = EndPosition.X - StartPosition.X;
            var Y = EndPosition.Y - StartPosition.Y;
            tt.X += X;
            tt.Y += Y;
        }

        // 重新给图像赋值Transform变换属性
        img.RenderTransform = tgnew;
    }
}

/// <summary>
/// 鼠标左键弹起，结束图片的拖动
/// </summary>
/// <param name="p"></param>
private void MouseLeftButtonUpCommand(object[] p)
{
    object sender = p[0];
    MouseButtonEventArgs e = p[1] as MouseButtonEventArgs;
    Image img = sender as Image;
    movingObject = null;
}

图像缩放：

界面上准备两个按钮，点击分别实现图像的放大和缩小。

/// <summary>
/// 图片放大
/// </summary>
/// <param name="img">被操作的前台Image控件</param>
public void ZoomIn(Image img)
{
    TransformGroup tg = img.RenderTransform as TransformGroup;
    var tgnew = tg.CloneCurrentValue();
    if (tgnew != null)
    {
        ScaleTransform st = tgnew.Children[1] as ScaleTransform;
        img.RenderTransformOrigin = new Point(0.5, 0.5);
        if (st.ScaleX > 0 && st.ScaleX <= 2.0)
        {
            st.ScaleX += 0.05;
            st.ScaleY += 0.05;
        }
        else if (st.ScaleX < 0 && st.ScaleX >= -2.0)
        {
            st.ScaleX -= 0.05;
            st.ScaleY += 0.05;
        }
    }

    // 重新给图像赋值Transform变换属性
    img.RenderTransform = tgnew;
}

/// <summary>
/// 图片缩小
/// </summary>
/// <param name="img">被操作的前台Image控件</param>
public void ZoomOut(Image img)
{
    TransformGroup tg = img.RenderTransform as TransformGroup;
    var tgnew = tg.CloneCurrentValue();
    if (tgnew != null)
    {
        ScaleTransform st = tgnew.Children[1] as ScaleTransform;
        img.RenderTransformOrigin = new Point(0.5, 0.5);
        if (st.ScaleX >= 0.2)
        {
            st.ScaleX -= 0.05;
            st.ScaleY -= 0.05;
        }
        else if (st.ScaleX <= -0.2)
        {
            st.ScaleX += 0.05;
            st.ScaleY -= 0.05;
        }
    }

    // 重新给图像赋值Transform变换属性
    img.RenderTransform = tgnew;
}

图像旋转：

界面上准备两个按钮，点击分别实现图像的左转和右转。

/// <summary>
/// 图片左转
/// </summary>
/// <param name="img">被操作的前台Image控件</param>
public void RotateLeft(Image img)
{
    TransformGroup tg = img.RenderTransform as TransformGroup;
    var tgnew = tg.CloneCurrentValue();
    if (tgnew != null)
    {
        RotateTransform rt = tgnew.Children[2] as RotateTransform;
        img.RenderTransformOrigin = new Point(0.5, 0.5);
        rt.Angle -= 5;
    }

    // 重新给图像赋值Transform变换属性
    img.RenderTransform = tgnew;
}

/// <summary>
/// 图片右转
/// </summary>
/// <param name="img">被操作的前台Image控件</param>
public void RotateRight(Image img)
{
    TransformGroup tg = img.RenderTransform as TransformGroup;
    var tgnew = tg.CloneCurrentValue();
    if (tgnew != null)
    {
        RotateTransform rt = tgnew.Children[2] as RotateTransform;
        img.RenderTransformOrigin = new Point(0.5, 0.5);
        rt.Angle += 5;
    }

    // 重新给图像赋值Transform变换属性
    img.RenderTransform = tgnew;
}