wpf 手指触摸图片放大缩小 设置放大缩小值

xaml代码：

<Window x:Class="WpfApp1.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid x:Name="mainGrid">
<Grid.Resources>
<TransformGroup x:Key="TfGroup">
<ScaleTransform ScaleX="1" ScaleY="1"/>
<TranslateTransform X="0" Y="0"/>
</TransformGroup>
</Grid.Resources>
<Grid.RowDefinitions>
<RowDefinition Height="50"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>

<!--<Button Grid.Row="0" Width="50" Height="30" Cursor="Hand" Background="Transparent" BorderThickness="0" Content="打开图片" Click="OpenImg_Click" x:Name="OpenImg" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="20,0,0,0"/>-->
<Label Content="缩放倍数：" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="130,0,0,0"/>
<TextBox x:Name="txtMinSize" Width="40" Height="30" VerticalContentAlignment="Center" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="200,0,0,0" TextChanged="txtMinSize_TextChanged" Text="0.1"/>
<Label Content="--" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="240,0,0,0"/>
<TextBox x:Name="txtMaxSize" Width="40" Height="30" VerticalContentAlignment="Center" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="260,0,0,0" TextChanged="txtMaxSize_TextChanged" Text="3"/>
<ScrollViewer x:Name="mainScrollv" HorizontalAlignment="Center" VerticalAlignment="Center" HorizontalScrollBarVisibility="Disabled"
VerticalScrollBarVisibility="Disabled" Cursor="SizeAll" Margin="0" Focusable="False" Grid.Row="1">
<ContentControl MouseLeftButtonDown="ContentControl_MouseLeftButtonDown"
MouseLeftButtonUp="ContentControl_MouseLeftButtonUp"
MouseMove="ContentControl_MouseMove"
MouseWheel="ContentControl_MouseWheel"
HorizontalAlignment="Center" VerticalAlignment="Center">
<Image x:Name="IMG"
Margin="0,0,0,0"
VerticalAlignment="Top"
Stretch="Fill"
HorizontalAlignment="Left"
Width="300"
Height="300"
RenderTransform="{StaticResource TfGroup}" Source="D:\SunTa,S10131.jpg" RenderOptions.BitmapScalingMode="NearestNeighbor"/>

</ContentControl>

</ScrollViewer>
</Grid>
</Window>

c#代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}

private bool mouseDown;
private Point mouseXY;
private double min = 0.1, max = 3.0;//最小/最大放大倍数

private void Domousemove(ContentControl img, MouseEventArgs e)
{
if (e.LeftButton != MouseButtonState.Pressed)
{
return;
}
var group = IMG.FindResource("TfGroup") as TransformGroup;
var transform = group.Children[1] as TranslateTransform;
var position = e.GetPosition(img);
transform.X -= mouseXY.X - position.X;
transform.Y -= mouseXY.Y - position.Y;
mouseXY = position;
}

private void DowheelZoom(TransformGroup group, Point point, double delta)
{
var pointToContent = group.Inverse.Transform(point);
var transform = group.Children[0] as ScaleTransform;
if (transform.ScaleX + delta < min) return;
if (transform.ScaleX + delta > max) return;
transform.ScaleX += delta;
transform.ScaleY += delta;
var transform1 = group.Children[1] as TranslateTransform;
transform1.X = -1 * ((pointToContent.X * transform.ScaleX) - point.X);
transform1.Y = -1 * ((pointToContent.Y * transform.ScaleY) - point.Y);
}

private void ContentControl_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var img = sender as ContentControl;
if (img == null)
{
return;
}
img.CaptureMouse();
mouseDown = true;
mouseXY = e.GetPosition(img);
}

private void ContentControl_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
var img = sender as ContentControl;
if (img == null)
{
return;
}
img.ReleaseMouseCapture();
mouseDown = false;
}

private void ContentControl_MouseMove(object sender, MouseEventArgs e)
{
var img = sender as ContentControl;
if (img == null)
{
return;
}
if (mouseDown)
{
Domousemove(img, e);
}
}

private void ContentControl_MouseWheel(object sender, MouseWheelEventArgs e)
{
var img = sender as ContentControl;
if (img == null)
{
return;
}
var point = e.GetPosition(img);
var group = IMG.FindResource("TfGroup") as TransformGroup;
var delta = e.Delta * 0.001;
DowheelZoom(group, point, delta);
}

//private void OpenImg_Click(object sender, RoutedEventArgs e)
//{
// // 在WPF中， OpenFileDialog位于Microsoft.Win32名称空间
// Microsoft.Win32.OpenFileDialog dialog = new Microsoft.Win32.OpenFileDialog();
// dialog.Filter = "Files (*.png)|*.png|Files(*.jpg)|*.jpg";
// if (dialog.ShowDialog() == true)
// {
// //MessageBox.Show(dialog.FileName);
// this.IMG.Source = new BitmapImage(new Uri(dialog.FileName));
// }
//}

private void Window_Loaded(object sender, RoutedEventArgs e)
{
setViewSize();
}
private void setViewSize()
{
mainScrollv.Width = this.ActualWidth;
mainScrollv.Height = this.ActualHeight - 50;
}

private void Window_SizeChanged(object sender, SizeChangedEventArgs e)
{
setViewSize();
}

private void txtMinSize_TextChanged(object sender, TextChangedEventArgs e)
{
this.min = double.Parse(txtMinSize.Text);
}

private void txtMaxSize_TextChanged(object sender, TextChangedEventArgs e)
{
this.max = double.Parse(txtMaxSize.Text);
}

private void Window_DragEnter(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
e.Effects = DragDropEffects.Link;//WinForm中为e.Effect = DragDropEffects.Link
else e.Effects = DragDropEffects.None;//WinFrom中为e.Effect = DragDropEffects.None

}

private void Window_Drop(object sender, DragEventArgs e)
{
string filename = ((System.Array)e.Data.GetData(DataFormats.FileDrop)).GetValue(0).ToString();
this.IMG.Source = new BitmapImage(new Uri(filename));
}

}
}