wpf实现简易画板功能（带截取画板，签名截图等等）

参照自：https://www.cnblogs.com/jixin/p/4730170.html
https://blog.csdn.net/u012408847/article/details/86482399

截图功能将会把红色方块区域内的内容截取下来，保存在img文件夹中。

window1.xaml

<Window x:Class="_1_5GraphicsWpf.Window1"
        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:_1_5GraphicsWpf"
        xmlns:cvr="clr-namespace:_1_5GraphicsWpf.ControlValidationRule"
        mc:Ignorable="d"
        Title="Window1" Height="450" Width="800">
    <Grid>
        <DockPanel  Background="AliceBlue">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="5*"></ColumnDefinition>
                    <ColumnDefinition Width="13*"></ColumnDefinition>
                    
                </Grid.ColumnDefinitions>
            
            <Canvas Grid.Column="1" x:Name="myCanvas"   DockPanel.Dock="Right" Background="LightGray" 
                    PreviewMouseLeftButtonDown="Canvas_PreviewMouseLeftButtonDown" PreviewMouseMove="Canvas_PreviewMouseMove"
                    MouseLeftButtonUp="MyCanvas_MouseLeftButtonUp" 
                    ></Canvas>
            
                <Grid DockPanel.Dock="Left" x:Name="LeftDockPanel">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"></ColumnDefinition>
                        <ColumnDefinition Width="3*"></ColumnDefinition>
                    </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                    <RowDefinition Height="30px"></RowDefinition>
                </Grid.RowDefinitions>
                <Label Grid.Column="0" Grid.Row="0">颜色œ˜œ˜œ˜œ˜</Label>
                <ComboBox x:Name="ComboColor" Grid.Row="0" Grid.Column="1" Margin="6 3"
                          SelectedValuePath="{Binding Path=ID}" SelectedIndex="{Binding Path=Combo_ColorIndex}" >
                    <ComboBox.ItemTemplate>
                        <DataTemplate>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock Text="{Binding Path=PColor}"></TextBlock>
                            </StackPanel>
                        </DataTemplate>
                    </ComboBox.ItemTemplate>
                </ComboBox>
                
                <Label Grid.Column="0" Grid.Row="1">线条粗细œ˜œ˜œ˜œ˜</Label>
                <TextBox x:Name="textBoxThick" Grid.Row="1"  Grid.Column="1" Margin="6,3" >
                    <TextBox.Text>
                        <Binding  Path="Thickness" NotifyOnValidationError="True" NotifyOnSourceUpdated="True" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
                            <Binding.ValidationRules>
                                <cvr:DataValidationRule ValidatesOnTargetUpdated="True"></cvr:DataValidationRule>
                        </Binding.ValidationRules>
                        </Binding>
                    </TextBox.Text>
                </TextBox>
                <Slider Minimum="0" Maximum="100" Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="2" Value="{Binding Path=Thickness, Mode=TwoWay}"></Slider>
                   

                    <Label Grid.Column="0" Grid.Row="3">样式œ˜œ˜œ˜œ˜</Label>
                    <ComboBox x:Name="ComboStyle" Grid.Row="3" Grid.Column="1" Margin="6 3"
                          SelectedValuePath="{Binding Path=ID}" SelectedIndex="{Binding Path=Combo_StyleIndex}" >
                        <ComboBox.ItemTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <TextBlock Text="{Binding Path=PStyle}"></TextBlock>
                                </StackPanel>
                            </DataTemplate>
                        </ComboBox.ItemTemplate>
                    </ComboBox>
                    <Button Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="2" Margin="10 3" Content="清除" Click="Button_Click"></Button>
                    <Button Grid.Row="5" Grid.Column="0" Grid.ColumnSpan="2" Margin="10 3" Content="截图" Click="Button_Click_1"></Button>
                   
                </Grid>

            </Grid>
        </DockPanel>
       
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
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 _1_5GraphicsWpf.ViewModel;
using _1_5GraphicsWpf.ControlValidationRule;
using System.Drawing;

namespace _1_5GraphicsWpf
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            Init();
        }
        ObservableCollection<VMColor> ColorCollection;
        ObservableCollection<VMStyle> StyleCollection;
        Global_Window1 GlobalVaries;

        void Init()
        {
             ColorCollection = new ObservableCollection<VMColor> {
                
                 new VMColor{ID = 0,PColor="默认"},
                 new VMColor{ID = 1,PColor="红色"},
                 new VMColor{ID = 2,PColor="绿色" }
             };
             StyleCollection = new ObservableCollection<VMStyle> {
             
                 new VMStyle{ID = 0,PStyle="平坦"},
                 new VMStyle{ID = 1,PStyle="直角"},
                 new VMStyle{ID = 2,PStyle="三角"},
                 new VMStyle{ID = 3,PStyle="圆形"}
             };

            GlobalVaries = new Global_Window1() {
                Combo_ColorIndex = 0,
                Combo_StyleIndex = 0,
                Thickness = 1
               
            };
            this.ComboColor.ItemsSource = ColorCollection;
            this.ComboStyle.ItemsSource = StyleCollection; 
            this.DataContext = GlobalVaries;
            this.textBoxThick.AddHandler(Validation.ErrorEvent,new RoutedEventHandler(this.ValidationError));
        }
        void ValidationError(object sender,RoutedEventArgs e)
        {
            TextBox obj = sender as TextBox;
            if (Validation.GetErrors(obj).Count>0)
            {
                obj.ToolTip = Validation.GetErrors(this.textBoxThick)[0].ErrorContent.ToString();
            }
        }
        System.Windows.Point startPoint;
        List<System.Windows.Point> pointList = new List<System.Windows.Point>();
        private void Canvas_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            startPoint = e.GetPosition(myCanvas);
        }

        private void Canvas_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                // 返回指针相对于Canvas的位置
                System.Windows.Point point = e.GetPosition(myCanvas);

                if (pointList.Count == 0)
                {
                    // 加入起始点
                    pointList.Add(new System.Windows.Point(this.startPoint.X, this.startPoint.Y));
                }
                else
                {
                    // 加入移动过程中的point  颜色
                    pointList.Add(point);
                }

                // 去重复点
                var disList = pointList.Distinct().ToList();
                var count = disList.Count(); // 总点数
                if (point != this.startPoint && this.startPoint != null)
                {
                    var l = new Line();
                    
                    //string color = (ComboColor.SelectedItem as ComboBoxItem).Content as string;
                    int color = int.Parse((ComboColor.SelectedValue as VMColor).ID.ToString());
                    switch (color)
                    {
                        case 0:
                            l.Stroke = System.Windows.Media.Brushes.Black;
                            break;
                        case 1:
                            l.Stroke = System.Windows.Media.Brushes.Red;
                            break;
                        case 2:
                            l.Stroke = System.Windows.Media.Brushes.Green;
                            break;

                        default:
                            l.Stroke = System.Windows.Media.Brushes.Black;
                            break;
                    }
                    int style = int.Parse((ComboStyle.SelectedValue as VMStyle).ID.ToString());
                    switch (style)
                    {
                        case 0:
                            l.StrokeDashCap = PenLineCap.Flat;
                            l.StrokeStartLineCap = PenLineCap.Flat;
                            l.StrokeEndLineCap = PenLineCap.Flat;
                            break;
                        case 1:
                            l.StrokeDashCap = PenLineCap.Square;
                            l.StrokeStartLineCap = PenLineCap.Square;
                            l.StrokeEndLineCap = PenLineCap.Square;
                            break;
                        case 2:
                            l.StrokeDashCap = PenLineCap.Triangle;
                            l.StrokeStartLineCap = PenLineCap.Triangle;
                            l.StrokeEndLineCap = PenLineCap.Triangle;
                            break;
                        case 3:
                            l.StrokeDashCap = PenLineCap.Round;
                            l.StrokeStartLineCap = PenLineCap.Round;
                            l.StrokeEndLineCap = PenLineCap.Round;
                            break;

                        default:
                            l.StrokeDashCap = PenLineCap.Round;
                            l.StrokeStartLineCap = PenLineCap.Round;
                            l.StrokeEndLineCap = PenLineCap.Round;
                            break;
                    }
                     //l.StrokeLineJoin = PenLineJoin.Round;
                     //l.StrokeStartLineCap = PenLineCap.Triangle;

                    l.StrokeThickness = this.GlobalVaries.Thickness ;
                    
                    if (count < 2)
                        return;
                    l.X1 = disList[count - 2].X;  // count-2  保证 line的起始点为点集合中的倒数第二个点。
                    l.Y1 = disList[count - 2].Y;
                    // 终点X,Y 为当前point的X,Y 
                    l.X2 = point.X;
                    l.Y2 = point.Y;
                    myCanvas.Children.Add(l);
                }
            }

        }

        private void MyCanvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            pointList.Clear();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            this.myCanvas.Children.Clear();//清除
            pointList.Clear();
        }

        #region 截图
        public static Shape CreateShape()
        {
            //矩形区域
            return new System.Windows.Shapes.Rectangle() { Fill = null, Stroke = System.Windows.Media.Brushes.Red, StrokeThickness = 1 };
            //圆形区域
            //return new System.Windows.Shapes.Ellipse() { Fill = null, Stroke = System.Windows.Media.Brushes.Red, StrokeThickness = 1 };

        }
        bool drawFlag = false;
        Shape insertShape;
        System.Windows.Point startPosition;




        private void Mask_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            insertShape = CreateShape();
            if (insertShape != null)
            {
                drawFlag = true;
                Canvas board = sender as Canvas;
                //board.Children.Clear();
                startPosition = e.GetPosition(board);
                insertShape.Opacity = 1;
                Canvas.SetLeft(insertShape, e.GetPosition(board).X);
                Canvas.SetTop(insertShape, e.GetPosition(board).Y);
                board.Children.Add(insertShape);
            }
        }

        private void image_MouseMove(object sender, MouseEventArgs e)
        {
            Canvas board = sender as Canvas;
            if (drawFlag && insertShape != null)
            {
                if (e.GetPosition(board).X > startPosition.X)
                {
                    insertShape.Width = e.GetPosition(board).X - startPosition.X;
                    //Canvas.SetRight(insertShape, startPosition.X);


                }
                else
                {
                    insertShape.Width = startPosition.X - e.GetPosition(board).X;
                    Canvas.SetLeft(insertShape, e.GetPosition(board).X);
                }
                if (e.GetPosition(board).Y > startPosition.Y)
                {
                    insertShape.Height = e.GetPosition(board).Y - startPosition.Y;
                    //Canvas.SetBottom(insertShape, startPosition.Y);
                }
                else
                {
                    insertShape.Height = startPosition.Y - e.GetPosition(board).Y;
                    Canvas.SetTop(insertShape, e.GetPosition(board).Y);
                }
            }
        }

        private void Mask_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            Canvas board = sender as Canvas;
            System.Windows.Point position = board.PointToScreen(new System.Windows.Point(0, 0));
            drawFlag = false;
            int width = (int)insertShape.Width +150 ;
            int height = (int)insertShape.Height +110 ;
            System.Drawing.Size size = new System.Drawing.Size(width, height);
            
            int startX = (e.GetPosition(board).X < startPosition.X) ? (int)e.GetPosition(board).X  : (int)startPosition.X ;
            int startY = (e.GetPosition(board).Y < startPosition.Y) ? (int)e.GetPosition(board).Y  : (int)startPosition.Y ;

            //int endX = (e.GetPosition(board).X > startPosition.X) ? (int)e.GetPosition(board).X + 10 : (int)startPosition.X + 10;
            //int endY = (e.GetPosition(board).Y > startPosition.Y) ? (int)e.GetPosition(board).Y + 10 : (int)startPosition.Y + 10;

            if (insertShape != null)
            {
                insertShape.Opacity = 1;
                System.Windows.Point p = e.GetPosition(board);
                
                //BitmapSource  memory = new Bitmap(width, height);
                //Graphics g = Graphics.FromImage(memory);
                //g.CopyFromScreen(this.Location.X + 1, this.Location.Y + 1, 0, 0, new System.Drawing.Size(width, height));
                Clipboard.SetImage(memory);//把图片放到剪切板中
                //bmp.Save("C:\\Screenshots\\" + filename);

                using (Bitmap bmp = new Bitmap(width, height))
                {

                    using (Graphics g = Graphics.FromImage(bmp))
                    {
                        String filename = "ScreenCapture-" + DateTime.Now.ToString("ddMMyyyy-hhmmss") + ".png";

                        g.CopyFromScreen(startX+(int)position.X, startY+(int)position.Y, 0, 0, size);
                        bmp.Save("..\\..\\img\\" + filename);
                        Button_Click_2();

                    }
                }
            }
        }
        #endregion

        bool canShot = false;
        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            this.myCanvas.MouseLeftButtonDown += Mask_MouseLeftButtonDown;
            this.myCanvas.MouseMove += image_MouseMove;
            this.myCanvas.MouseLeftButtonUp += Mask_MouseLeftButtonUp;

            this.myCanvas.PreviewMouseLeftButtonDown -= Canvas_PreviewMouseLeftButtonDown;
            this.myCanvas.PreviewMouseMove -= Canvas_PreviewMouseMove;
            this.myCanvas.MouseLeftButtonUp -= MyCanvas_MouseLeftButtonUp;
            canShot = true;
        }

        private void Button_Click_2()
        {
            if (canShot ==true)
            {
                this.myCanvas.MouseLeftButtonDown -= Mask_MouseLeftButtonDown;
                this.myCanvas.MouseMove -= image_MouseMove;
                this.myCanvas.MouseLeftButtonUp -= Mask_MouseLeftButtonUp;

                this.myCanvas.PreviewMouseLeftButtonDown += Canvas_PreviewMouseLeftButtonDown;
                this.myCanvas.PreviewMouseMove += Canvas_PreviewMouseMove;
                this.myCanvas.MouseLeftButtonUp += MyCanvas_MouseLeftButtonUp;
            }
            canShot = false;


        }
    }
}