在WPF中自定义Image控件实现图像缩放与平移

<UserControl
    x:Class="HalconDemo.ImageUserControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:HalconDemo"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    HorizontalAlignment="Stretch"
    VerticalAlignment="Stretch"
    d:DesignHeight="1024"
    d:DesignWidth="1920"
    mc:Ignorable="d">
    <Grid>
        <ContentControl
            Name="Part_ImageContainer"
            MaxWidth="1920"
            MaxHeight="1024"
            HorizontalAlignment="Left"
            VerticalAlignment="Top"
            HorizontalContentAlignment="Stretch"
            VerticalContentAlignment="Stretch"
            ClipToBounds="True"
            Cursor="Hand">
            <Image
                Name="image"
                HorizontalAlignment="Left"
                VerticalAlignment="Top"
                RenderOptions.BitmapScalingMode="NearestNeighbor">
                <Image.RenderTransform>
                    <TransformGroup x:Name="group">
                        <ScaleTransform x:Name="scaler" />
                        <TranslateTransform x:Name="transer" />
                    </TransformGroup>
                </Image.RenderTransform>
            </Image>
        </ContentControl>
    </Grid>
</UserControl>

/// <summary>
/// ImageUserControl.xaml 的交互逻辑
/// </summary>
public partial class ImageUserControl : UserControl
{
    /// <summary>
    /// 鼠标是否按下
    /// </summary>
    private bool mouseDown;


    /// <summary>
    /// 移动图片前，按下鼠标左键时，鼠标相对于Part_ImageContainer的点
    /// </summary>
    Point moveStart;

    public ImageUserControl()
    {
        InitializeComponent();
    }

    ~ImageUserControl()
    {
        Part_ImageContainer.MouseLeftButtonDown -= ImgMouseLeftButtonDown;
        Part_ImageContainer.MouseMove -= ImgMouseMove;
        Part_ImageContainer.MouseUp -= ImgMouseUp;
    }

    /// <summary>
    /// 初始化加载图像
    /// </summary>
    /// <param name="filePath">图像路径</param>
    /// <param name="IsMove">是否移动，true是,false否</param>
    public void InitImage(string filePath,bool IsMove = true)
    {
        if (IsMove)
        {
            Part_ImageContainer.MouseLeftButtonDown += ImgMouseLeftButtonDown;
            Part_ImageContainer.MouseMove += ImgMouseMove;
            Part_ImageContainer.MouseUp += ImgMouseUp;
        }
        image.Source = new BitmapImage(new Uri(filePath, UriKind.Absolute));
    }

    private void ImgMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        //尝试将鼠标强制捕获到此元素
        Part_ImageContainer.CaptureMouse();
        mouseDown = true;
        moveStart = e.GetPosition(Part_ImageContainer);
    }

    private void ImgMouseMove(object sender, MouseEventArgs e)
    {
        var mouseEnd = e.GetPosition(Part_ImageContainer);           // 鼠标移动时，获取鼠标相对图片容器的点
        if (mouseDown)
        {
            if (e.LeftButton == MouseButtonState.Pressed)           // 按下鼠标左键，移动图片
            {
                DoMove(mouseEnd);
            }
        }
    }

    private void ImgMouseUp(object sender, MouseButtonEventArgs e)
    {
        Part_ImageContainer.ReleaseMouseCapture();
        mouseDown = false;
    }

    private void ImgMouseWheel(object sender, MouseWheelEventArgs e)
    {
        var point = e.GetPosition(image);
        double delta = e.Delta * 0.002;
        DoScale(point, delta);
    }
    /// <summary>
    /// 缩放图片。最小为0.1倍，最大为30倍
    /// </summary>
    /// <param name="point">相对于图片的点，以此点为中心缩放</param>
    /// <param name="delta">缩放的倍数增量</param>
    private void DoScale(Point point, double delta)
    {
        // 限制最大、最小缩放倍数
        if (scaler.ScaleX + delta < 0.1 || scaler.ScaleX + delta > 30) return;

        scaler.ScaleX += delta;
        scaler.ScaleY += delta;

        transer.X -= point.X * delta;
        transer.Y -= point.Y * delta;
    }

    /// <summary>
    /// 移动图片
    /// </summary>
    /// <param name="moveEndPoint">移动图片的终点（相对于Part_ImageContainer）</param>
    private void DoMove(Point moveEndPoint)
    {
        // 考虑到旋转的影响，因此将两个点转换到Part_Image坐标系，计算x、y的增量
        Point start = Part_ImageContainer.TranslatePoint(moveStart, image);
        Point end = Part_ImageContainer.TranslatePoint(moveEndPoint, image);


        // 判断一下，如果scale很大的时候，移动会很迟缓。此时应该将移动放大
        if (scaler.ScaleX > 7)
        {
            transer.X += (end.X - start.X) * 4;
            transer.Y += (end.Y - start.Y) * 4;
        }
        else if (scaler.ScaleX > 5)
        {
            transer.X += (end.X - start.X) * 3;
            transer.Y += (end.Y - start.Y) * 3;
        }
        else if (scaler.ScaleX > 3)
        {
            transer.X += (end.X - start.X) * 2;
            transer.Y += (end.Y - start.Y) * 2;
        }
        else if (scaler.ScaleX < 0.5)
        {
            transer.X += (end.X - start.X) * 0.5;
            transer.Y += (end.Y - start.Y) * 0.5;
        }
        else
        {
            transer.X += (end.X - start.X);
            transer.Y += (end.Y - start.Y);
        }
        moveStart = moveEndPoint;

        // 以下代码，抄的https://blog.csdn.net/weixin_42975610/article/details/113741534

        // W+w > 2*move_x > -((2*scale-1)*w + W)  水平平移限制条件
        // H+h > 2*move_y > -((2*scale-1)*h + H)  垂直平移限制条件

        if (transer.X * 2 > image.ActualWidth + Part_ImageContainer.ActualWidth - 20)
            transer.X = (image.ActualWidth + Part_ImageContainer.ActualWidth - 20) / 2;

        if (-transer.X * 2 > (2 * scaler.ScaleX - 1) * image.ActualWidth + Part_ImageContainer.ActualWidth - 20)
            transer.X = -((scaler.ScaleX - 0.5) * image.ActualWidth + Part_ImageContainer.ActualWidth / 2 - 10);

        if (transer.Y * 2 > image.ActualHeight + Part_ImageContainer.ActualHeight - 20)
            transer.Y = (image.ActualHeight + Part_ImageContainer.ActualHeight - 20) / 2;

        if (-transer.Y * 2 > (2 * scaler.ScaleY - 1) * image.ActualHeight + Part_ImageContainer.ActualHeight - 20)
            transer.Y = -((scaler.ScaleY - 0.5) * image.ActualHeight + Part_ImageContainer.ActualHeight / 2 - 10);
    }

    /// <summary>
    /// 图像缩放
    /// </summary>
    /// <param name="point">当前坐标</param>
    /// <param name="scale">缩放倍数</param>
    public void ImageScale(Point point, double scale)
    {
        DoScale(point, scale);
    }
}

//控件引用
 <Canvas
     x:Name="canvas"
     Grid.Row="1"
     Background="Black">
     <HalconDemo:ImageUserControl
         x:Name="ImageUserControl"
         Grid.Row="1"
         Width="{Binding ElementName=canvas, Path=ActualWidth}"
         Height="{Binding ElementName=canvas, Path=ActualHeight}"
         MouseWheel="ImageUserControl_MouseWheel" />
 </Canvas>
//鼠标滚动缩放
 private void ImageUserControl_MouseWheel(object sender, MouseWheelEventArgs e)
 {
     var point = e.GetPosition(image);
     double delta = e.Delta * 0.002;
     ImageUserControl.ImageScale(point, delta);
 }