<Window x:Class="Lenovo.YogaPaster.ImageEditWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="ImageEditWindow" Height="300" Width="300">
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="20*"/>
      <RowDefinition  Height="*"/>
    </Grid.RowDefinitions>
    <Canvas x:Name="canvas"
      Background="Yellow" />
    <Button Content="保存成圖片" Click="Button_Click_1" Grid.Row="1" HorizontalAlignment="Center" VerticalAlignment="Center"/>
  </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
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.Shapes;
using Lenovo.YP.Utils;
using Microsoft.Win32;
using Point = System.Windows.Point;

namespace Lenovo.YogaPaster
{
  /// <summary>
  /// ImageEditWindow.xaml 的交互邏輯
  /// </summary>
  public partial class ImageEditWindow : Window
  {
    public ImageEditWindow()
    {
      InitializeComponent();
      this.Loaded += (sender, e) =>
      {
        canvas.MouseLeftButtonDown += canvas_MouseLeftButtonDown;
      };
    }
    private void canvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
      PhotoEditHelper.CommomMaxZIndex++;
      var image = new MoveImage { ContainerCanvas = canvas };
      Point point = e.GetPosition(canvas);
      image.CreateImage(point);
    }
    /// <summary>
    /// 保存方法
    /// </summary>
    public void SavePicture()
    {
      //TODO: openFile對話框
      SaveFileDialog saveFileDialog = new SaveFileDialog();
      saveFileDialog.FileName = "圖片"; // Default file name
      saveFileDialog.DefaultExt = ".bmp"; // Default file extension
      saveFileDialog.Filter = "圖片文件 (.bmp)|*.bmp"; // Filter files by extension

      // Show save file dialog box
      Nullable<bool> result = saveFileDialog.ShowDialog();

      // Process save file dialog box results
      if (result == true)
      {
        // Save document
        string filename = saveFileDialog.FileName;
        if (File.Exists(filename))
        {
          File.Delete(filename);
        }
        BitmapSource bitmapSource = PictureMergeHelper.CreateNotRanderElementScreenshot(canvas, 1800, 1080);
        BitmapEncoder bitmapEncoder = new BmpBitmapEncoder();
        bitmapEncoder.Frames.Add(BitmapFrame.Create(bitmapSource));
        FileStream fileStream = new FileStream(filename, FileMode.Create);
        bitmapEncoder.Save(fileStream);
        fileStream.Dispose();
      }
    }

    private void Button_Click_1(object sender, RoutedEventArgs e)
    {
      SavePicture();
    }
  }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace Lenovo.YP.Utils
{
  /// <summary>
  /// 添加一個image控件，并實現拖動效果
  /// </summary>
  public class MoveImage
  {
    #region 字段
    private int m_ZIndex;
    /// <summary>
    /// 當前圖章的位置
    /// </summary>
    ///
    /// <summary>
    /// 旋轉圖標的起始位置
    /// </summary>
    private Point m_ImageRoundStartOffset;
    /// <summary>
    /// 旋轉圖標的當前位置
    /// </summary>
    private Point m_ImageRoundOffset;
    /// <summary>
    /// 標識圖章是否被拖拽
    /// </summary>
    private bool m_IsDragging;
    /// <summary>
    /// 標識旋轉圖標是否被是否被拖拽
    /// </summary>
    private bool m_IsimageRoundDragging;
    /// <summary>
    /// 圖章的父容器
    /// </summary>
    public Canvas ContainerCanvas { get; set; }
    /// <summary>
    /// 圖章圖片
    /// </summary>
    private Image m_FlogImage;
    /// <summary>
    /// 旋轉按鈕圖片
    /// </summary>
    private Image m_RotateImage;
    /// <summary>
    /// 圖章和旋轉圖片的容器
    /// </summary>
    private Grid m_MoveImageGrid;
    /// <summary>
    /// 選轉
    /// </summary>
    private RotateTransform m_ImageRotate;
    /// <summary>
    /// 縮放
    /// </summary>
    private ScaleTransform m_ImageScale;
    /// <summary>
    /// 上次位置
    /// </summary>
    private Point m_OldPos;
    #endregion

    public MoveImage()
    { }
    /// <summary>
    /// 創建一個圖標
    /// </summary>
    /// <param name="position">圖標的位置</param>
    public void CreateImage(Point position)
    {
      #region 設置布局
      m_FlogImage = new Image
      {
        //Width = 100,
        //Height = 100,
        Source = new BitmapImage(new Uri("/Images/shuzi.jpg", UriKind.RelativeOrAbsolute))
      };
      m_RotateImage = new Image
      {
        Width = 20,
        Height = 20,
        Source = new BitmapImage(new Uri("/Images/round.jpg", UriKind.RelativeOrAbsolute))
      };
      m_RotateImage.HorizontalAlignment = HorizontalAlignment.Right;
      m_RotateImage.VerticalAlignment = VerticalAlignment.Bottom;
      m_RotateImage.Visibility = Visibility.Hidden;
      m_MoveImageGrid = new Grid();
      m_MoveImageGrid.Width = 110;
      m_MoveImageGrid.Height = 110;
      m_MoveImageGrid.Children.Add(m_FlogImage);
      m_MoveImageGrid.Children.Add(m_RotateImage);
      m_MoveImageGrid.MouseEnter += RootGridMouseEnter;
      m_MoveImageGrid.MouseLeave += RootGridMouseLeave;
      m_RotateImage.MouseLeftButtonDown += imageRound_MouseLeftButtonDown;
      m_RotateImage.MouseMove += imageRound_MouseMove;
      m_RotateImage.MouseLeftButtonUp += imageRound_MouseLeftButtonUp;
      // Image in den Vordergrund bringen
      Canvas.SetZIndex(m_MoveImageGrid, m_ZIndex++);
      #endregion
      // Event Handler für das Image installieren
      m_MoveImageGrid.MouseLeftButtonDown += RootGridMouseLeftButtonDown;
      m_MoveImageGrid.MouseLeftButtonUp += RootGridMouseLeftButtonUp;
      m_MoveImageGrid.MouseMove += RootGridMouseMove;
      // Image leicht transparent machen
      m_MoveImageGrid.Opacity = 0.8;
      m_ImageRotate = new RotateTransform(0, 0, 0);
      m_ImageScale = new ScaleTransform();
      //m_ImageScale.ScaleX = 1;
      //m_ImageScale.ScaleY = 1;
      TransformGroup transformGroup = new TransformGroup();
      transformGroup.Children.Add(m_ImageRotate);
      transformGroup.Children.Add(m_ImageScale);
      m_MoveImageGrid.RenderTransform = transformGroup;
      //m_ImageScale111 = new ScaleTransform();
      //m_ImageScale111.ScaleX = 0.5;
      //m_ImageScale111.ScaleY = 0.5;
      //imageRound.RenderTransform = m_ImageScale111;
      m_MoveImageGrid.RenderTransformOrigin = new Point(0.5, 0.5);
      // Image positionieren
      var pos = position;
      Canvas.SetLeft(m_MoveImageGrid, pos.X - (m_MoveImageGrid.Width / 2));
      Canvas.SetTop(m_MoveImageGrid, pos.Y - (m_MoveImageGrid.Height / 2));
      // Image zum Canvas hinzufügen
      ContainerCanvas.Children.Add(m_MoveImageGrid);
    }

    /// <summary>
    /// 控制旋轉圖標隱藏
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void RootGridMouseLeave(object sender, MouseEventArgs e)
    {
      m_RotateImage.Visibility = Visibility.Hidden;
    }

    /// <summary>
    /// 控制選擇圖標顯示
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void RootGridMouseEnter(object sender, MouseEventArgs e)
    {
      m_RotateImage.Visibility = Visibility.Visible;
    }

    #region 控制蓋章的移動
    private void RootGridMouseMove(object sender, MouseEventArgs e)
    {
      if (m_IsDragging)
      {
        var pos = e.GetPosition(ContainerCanvas);
        Canvas.SetLeft(m_MoveImageGrid, Canvas.GetLeft(m_MoveImageGrid) + pos.X - m_OldPos.X);
        Canvas.SetTop(m_MoveImageGrid, Canvas.GetTop(m_MoveImageGrid) + pos.Y - m_OldPos.Y);
        m_OldPos = pos;
      }
    }

    private void RootGridMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
      var grid = sender as Grid;

      // Canvas.SetZIndex(image, m_ZIndex++);
      // Bild wieder leicht transparent machen
      grid.Opacity = 0.8;
      grid.ReleaseMouseCapture();
      m_IsDragging = false;
    }

    private void RootGridMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {

      var grid = sender as Grid;

      // auf "nicht"-transparent setzen
      grid.Opacity = 1;

      // Position des Pointers relativ zum Bild speichern
      m_OldPos = e.GetPosition(ContainerCanvas);

      // isDragging auf true setzen für MouseMove
      m_IsDragging = true;
      // Image in den Vordergrund bringen
      Canvas.SetZIndex(grid, PhotoEditHelper.CommomMaxZIndex++);
      // Den Pointer einfangen. Bei schnellen Bewegungen kann der
      // Pointer aus dem Image bewegt werden. Damit die Pointer-
      // Events weiterhin stattfinden, wird der Pointer eingefangen. 
      grid.CaptureMouse();
      // als behandelt markieren, damit nicht noch der
      // PointerPressed-Event Handler des Canvas aufgerufen wird.
      e.Handled = true;
    }
    #endregion

    #region 控制圖章的旋轉
    private void imageRound_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
      var image = sender as Image;

      m_MoveImageGrid.Opacity = 1;
      image.ReleaseMouseCapture();
      m_IsimageRoundDragging = false;
    }

    private void imageRound_MouseMove(object sender, MouseEventArgs e)
    {
      if (m_IsimageRoundDragging)
      {
        //鼠標當前點的坐標
        m_ImageRoundOffset = e.GetPosition(ContainerCanvas);
        m_ImageScale.ScaleX =
          m_ImageScale.ScaleY = GetLength(currCenter, m_ImageRoundStartOffset, m_ImageRoundOffset);
        m_ImageRotate.Angle = GetAngle(currCenter, m_ImageRoundStartOffset, m_ImageRoundOffset) - 45;
      }
    }

    private Point currCenter;
    private void imageRound_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
      var image = sender as Image;
      m_MoveImageGrid.Opacity = 1;

      //中心點坐標
      currCenter = new Point(Canvas.GetLeft(m_MoveImageGrid) + m_MoveImageGrid.Width / 2, Canvas.GetTop(m_MoveImageGrid) + m_MoveImageGrid.Height / 2);
      m_ImageRoundStartOffset = new Point(currCenter.X + m_MoveImageGrid.Width / 2, currCenter.Y);
      m_IsimageRoundDragging = true;
      Canvas.SetZIndex(m_MoveImageGrid, PhotoEditHelper.CommomMaxZIndex++);
      image.CaptureMouse();
      e.Handled = true;
    }

    /// 根據余弦定理求兩個線段夾角
    /// </summary> 
    /// <param name="origin">原點</param> 
    /// <param name="start">start點</param> 
    /// <param name="end">end點</param> 
    /// <returns></returns> 
    private double GetAngle(Point origin, Point start, Point end)
    {
      double cosfi = 0, fi = 0, norm = 0;
      double dsx = start.X - origin.X;
      double dsy = start.Y - origin.Y;
      double dex = end.X - origin.X;
      double dey = end.Y - origin.Y;

      cosfi = dsx * dex + dsy * dey;
      norm = (dsx * dsx + dsy * dsy) * (dex * dex + dey * dey);
      if (norm == 0) return 0; // origin和end坐標一樣
      cosfi /= Math.Sqrt(norm);

      if (cosfi >= 1.0) return 0;
      if (cosfi <= -1.0) return 180;
      fi = Math.Acos(cosfi);

      double angle = 180 * fi / Math.PI;

      if (dey > 0)
      {
        return angle;
      }
      return -angle;
    }

    private double GetLength(Point origin, Point start, Point end)
    {
      double dex = end.X - origin.X;
      double dey = end.Y - origin.Y;
      double dsx = start.X - origin.X;
      double dsy = start.Y - origin.Y;
      double startLength = Math.Sqrt(Math.Pow(dsx, 2) + Math.Pow(dsy, 2));
      double endLength = Math.Sqrt(Math.Pow(dex, 2) + Math.Pow(dey, 2));
      return endLength / startLength;
    }

    #endregion
  }