WPF InkCanvas绘制矩形和椭圆

<window x:class="wpf_inkcanvas.roi_inkcanvas"
    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:wpf_inkcanvas"
    mc:ignorable="d"
    title="roi_inkcanvas" height="450" width="800">
  <grid>
    <grid.rowdefinitions>
      <rowdefinition/>
      <rowdefinition height="auto"/>
    </grid.rowdefinitions>
    <image name="imgmeasure" horizontalalignment="center" stretch="uniform"/>
    <inkcanvas name="inkcanvasmeasure" editingmode="none" background="transparent" strokes="{binding inkstrokes, mode=twoway}" horizontalalignment="center" 
          width="{binding elementname=imgmeasure, path=actualwidth}" height="{binding elementname=imgmeasure, path=actualheight}"
          mousedown="inkcanvasmeasure_mousedown" mousemove="inkcanvasmeasure_mousemove">
      <label content="{binding meainfo}" background="transparent" horizontalalignment="left" verticalalignment="top" margin="10" 
          fontsize="18" foreground="red" ishittestvisible="false"/>
    </inkcanvas>
    <stackpanel grid.row="1" orientation="horizontal">
      <button content="openfile" margin="5" horizontalalignment="left" fontsize="20" click="openfile_click"/>
      <togglebutton name="btnsquare" content="draw square" margin="5" horizontalalignment="left" fontsize="20" click="drawsquare_click"/>
      <togglebutton name="btnellipse" content="draw ellipse" margin="5" horizontalalignment="left" fontsize="20" click="drawellipse_click"/>
    </stackpanel>
  </grid>
</window>

using microsoft.win32;
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.ink;
using system.windows.input;
using system.windows.media;
using system.windows.media.imaging;
using system.windows.shapes;
 
namespace wpf_inkcanvas
{
  /// <summary>
  /// roi_inkcanvas.xaml 的交互逻辑
  /// </summary>
  public partial class roi_inkcanvas : window
  {
    private viewmodel viewmodel;
    private system.windows.point inip;
    public roi_inkcanvas()
    {
      initializecomponent();
 
      drawingattributes drawingattributes = new drawingattributes
      {
        color = colors.red,
        width = 2,
        height = 2,
        stylustip = stylustip.rectangle,
        //fittocurve = true,
        ishighlighter = false,
        ignorepressure = true,
 
      };
      inkcanvasmeasure.defaultdrawingattributes = drawingattributes;
 
      viewmodel = new viewmodel
      {
        meainfo = "测试······",
        inkstrokes = new strokecollection(),
      };
 
      datacontext = viewmodel;
    }
 
    private void openfile_click(object sender, routedeventargs e)
    {
      openfiledialog opendialog = new openfiledialog
      {
        filter = "image files (*.jpg)|*.jpg|image files (*.png)|*.png|image files (*.bmp)|*.bmp",
        title = "open image file"
      };
      if (opendialog.showdialog() == true)
      {
        bitmapimage image = new bitmapimage();
        image.begininit();
        image.urisource = new uri(opendialog.filename, urikind.relativeorabsolute);
        image.endinit();
        imgmeasure.source = image;
      }
    }
 
    private void drawsquare_click(object sender, routedeventargs e)
    {
      if (btnsquare.ischecked == true)
      {
        btnellipse.ischecked = false;
      }
    } 
 
    private void drawellipse_click(object sender, routedeventargs e)
    {
      if (btnellipse.ischecked == true)
      {
        btnsquare.ischecked = false;
      }
    }
 
    private list<system.windows.point> generateeclipsegeometry(system.windows.point st, system.windows.point ed)
    {
      double a = 0.5 * (ed.x - st.x);
      double b = 0.5 * (ed.y - st.y);
      list<system.windows.point> pointlist = new list<system.windows.point>();
      for (double r = 0; r <= 2 * math.pi; r = r + 0.01)
      {
        pointlist.add(new system.windows.point(0.5 * (st.x + ed.x) + a * math.cos(r), 0.5 * (st.y + ed.y) + b * math.sin(r)));
      }
      return pointlist;
    }
    private void inkcanvasmeasure_mousedown(object sender, mousebuttoneventargs e)
    {
      if (e.leftbutton == mousebuttonstate.pressed)
      {
        inip = e.getposition(inkcanvasmeasure);
      }
    }
 
    private void inkcanvasmeasure_mousemove(object sender, mouseeventargs e)
    {
      if (e.leftbutton == mousebuttonstate.pressed)
      {
        // draw square
        if (btnsquare.ischecked == true)
        {
          system.windows.point endp = e.getposition(inkcanvasmeasure);
          list<system.windows.point> pointlist = new list<system.windows.point>
          {
            new system.windows.point(inip.x, inip.y),
            new system.windows.point(inip.x, endp.y),
            new system.windows.point(endp.x, endp.y),
            new system.windows.point(endp.x, inip.y),
            new system.windows.point(inip.x, inip.y),
          };
          styluspointcollection point = new styluspointcollection(pointlist);
          stroke stroke = new stroke(point)
          {
            drawingattributes = inkcanvasmeasure.defaultdrawingattributes.clone()
          };
          viewmodel.inkstrokes.clear();
          viewmodel.inkstrokes.add(stroke);
        }
        // draw eclipse
        else if (btnellipse.ischecked == true)
        {
          system.windows.point endp = e.getposition(inkcanvasmeasure);
          list<system.windows.point> pointlist = generateeclipsegeometry(inip, endp);
          styluspointcollection point = new styluspointcollection(pointlist);
          stroke stroke = new stroke(point)
          {
            drawingattributes = inkcanvasmeasure.defaultdrawingattributes.clone()
          };
          viewmodel.inkstrokes.clear();
          viewmodel.inkstrokes.add(stroke);
        }
      }
    }
  }
}

using system;
using system.collections.generic;
using system.componentmodel;
using system.linq;
using system.text;
using system.threading.tasks;
using system.windows.ink;
 
namespace wpf_inkcanvas
{
  class viewmodel : inotifypropertychanged
  {
    public event propertychangedeventhandler propertychanged;
 
    protected virtual void onpropertychanged(string propertyname = null)
    {
      if (propertychanged != null)
        propertychanged.invoke(this, new propertychangedeventargs(propertyname));
    }
 
    private string meainfo;
    public string meainfo
    {
      get => meainfo;
      set
      {
        meainfo = value;
        onpropertychanged("meainfo");
      }
    }
 
    private strokecollection inkstrokes;
    public strokecollection inkstrokes
    {
      get { return inkstrokes; }
      set
      {
        inkstrokes = value;
        onpropertychanged("inkstrokes");
      }
    }
  }
}