画线缩放、瞳距缩放、Line延长到指定长度，内附效果，源码供应，解压就跑

前言

公司项目需要做个画线缩放，我司称之为瞳距缩放，简而言之就是：2张图，从第一张图画一条线，再从第二个图画一条线，第二条线以第一条为基准，延长到一致的长度，并同比缩放图片；文字太枯燥，请先实例图

例子1：以皮卡丘为例，我要把路飞的拳头缩放到皮卡丘头那么大

例子2：以皮卡丘的基准，缩小路飞，与其身高一致

好了，相比看了上面的2个效果图，就明白了大致意思，这个demo可以获得，Canvas里面的Line如何顺着线条方向，无限延伸的解决方案，以及画线缩放等...

会运用到高中数学知识，三角函数知识点，所以不熟悉的朋友，需要先温习，这样吧，我带大家温习下，反正工作忙完了，写博客和网友分享经验是最愉悦的事儿...

三角函数必要知识点温习

tan：对边 / 临边 tanA = BC / AC

sin：对边 / 斜边 sinA = BC / AB

cos：临边 / 斜边 cosA = AC / AB

已知边 BC 、AC，求角A的度数 ∠A = Math.Atan(BC / AC); 这是最关键的，获取A的角度就解决了所有，起初我还是想了很久的，年龄一大，以前的事就记不得了，划重点这里

好了，三角函数的知识温习到这里就足矣了，想象一下，把这个三角形放到程序的坐标系中，细细品，假如用户随意画的线就是AB，在画好的基础上进行延长.......细细品....

画线缩放，难点就是，如何让第二条线延长

请看图

已知了A点B点的坐标，通过坐标系，就能换算出BC边和AC的长度

运用三角函数，∠A的度数就等于：Math.Atan(BC / AC);

拿到的∠A，一切都变得好说了

比如，AB=100

sinA = BC / AB -----> sinA = BC / 100 ----> BC = sinA * 100

BC = 100 * Math.Sin(∠A)

cosA = AC / AB ----> cosA = AC / 100 ----> AC = cosA * 100

AC = 100 * Math.Cos(∠A)

BC、AC边都拿到，相信朋友们能转换成Point了

好了，上面都是知识点，很枯燥，程序员还是看代码吧，总归是要代码实现的

 1 <Window x:Class="PupilDistanceDemo.MainWindow"
 2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 5         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6         xmlns:local="clr-namespace:PupilDistanceDemo"
 7         mc:Ignorable="d"
 8         WindowStartupLocation="CenterScreen"
 9         Title="瞳距缩放" Height="450" Width="800">
10     <Grid>
11         <Canvas Background="#0D1728" x:Name="canvas">
12             <Image Source="2.jpg" x:Name="img1" Stretch="Fill" Width="300"  Canvas.Top="100" Canvas.Left="50" />
13             <Image Source="1.jpg" x:Name="img2" Stretch="Fill" Width="200" Canvas.Top="100" Canvas.Left="400" />
14         </Canvas>
15         <StackPanel Orientation="Horizontal">
16             <Button Margin="5" VerticalAlignment="Top" Click="Button_Click">启动瞳距</Button>
17             <Button Margin="5" VerticalAlignment="Top" Click="Button_Click_1">关闭瞳距</Button>
18             <Button Margin="5" VerticalAlignment="Top" Click="Button_Click_2">瞳距计算</Button>
19             <Button Margin="5" VerticalAlignment="Top" Click="Button_Click_3">重置</Button>
20             <StackPanel VerticalAlignment="Top">
21                 <TextBlock Text="{Binding ElementName=img2,Path=ActualWidth}" Foreground="Red" />
22                 <TextBlock Text="{Binding ElementName=img2,Path=ActualHeight}" Foreground="Red" />
23             </StackPanel>
24         </StackPanel>
25     </Grid>
26 </Window>

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using System.Threading.Tasks;
  6 using System.Windows;
  7 using System.Windows.Controls;
  8 using System.Windows.Data;
  9 using System.Windows.Documents;
 10 using System.Windows.Input;
 11 using System.Windows.Media;
 12 using System.Windows.Media.Imaging;
 13 using System.Windows.Navigation;
 14 using System.Windows.Shapes;
 15 
 16 namespace PupilDistanceDemo
 17 {
 18     /// <summary>
 19     /// MainWindow.xaml 的交互逻辑
 20     /// </summary>
 21     public partial class MainWindow : Window
 22     {
 23         bool isLeftButtonDown = false;
 24         Image image;
 25 
 26         bool isPupilDistance = false;
 27         Size size;
 28 
 29         Point currentPoint;
 30 
 31         public MainWindow()
 32         {
 33             InitializeComponent();
 34 
 35             img1.MouseLeftButtonDown += Img_MouseLeftButtonDown;
 36             img1.MouseMove += Img_MouseMove;
 37             img1.MouseLeftButtonUp += Img_MouseLeftButtonUp;
 38 
 39             img2.MouseLeftButtonDown += Img_MouseLeftButtonDown;
 40             img2.MouseMove += Img_MouseMove;
 41             img2.MouseLeftButtonUp += Img_MouseLeftButtonUp;
 42 
 43             this.Loaded += MainWindow_Loaded;
 44         }
 45 
 46         private void MainWindow_Loaded(object sender, RoutedEventArgs e)
 47         {
 48             size = new Size(img2.ActualWidth, img2.ActualHeight);
 49         }
 50 
 51         private void Img_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
 52         {
 53             isLeftButtonDown = false;
 54             image = null;
 55         }
 56 
 57         private void Img_MouseMove(object sender, MouseEventArgs e)
 58         {
 59             if (isLeftButtonDown && sender is Image imgc)
 60             {
 61                 var point = e.GetPosition(canvas);
 62                 if (isPupilDistance && imgc.Tag is Line line)
 63                 {
 64                     if (image.Equals(imgc))
 65                     {
 66                         var x = point.X;
 67                         var y = point.Y;
 68                         if (x > line.X1) x -= 2;
 69                         else x += 2;
 70                         if (y > line.Y1) y -= 2;
 71                         else y += 2;
 72                         line.X2 = x;
 73                         line.Y2 = y;
 74                     }
 75                 }
 76                 else if (sender is Image image)
 77                 {
 78                     image.SetValue(Canvas.LeftProperty, point.X - currentPoint.X);
 79                     image.SetValue(Canvas.TopProperty, point.Y - currentPoint.Y);
 80                 }
 81             }
 82         }
 83 
 84         private void Img_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
 85         {
 86             image = sender as Image;
 87             isLeftButtonDown = true;
 88             if (sender is Image imgc)
 89             {
 90                 currentPoint = e.GetPosition(imgc);
 91 
 92                 if (isPupilDistance)
 93                 {
 94                     if (imgc.Tag is Line line)
 95                     {
 96                         canvas.Children.Remove(line);
 97                     }
 98 
 99                     line = new Line();
100                     line.StrokeThickness = 2;
101                     line.Stroke = new SolidColorBrush(Colors.Red);
102                     var point = e.GetPosition(canvas);
103                     line.X1 = point.X - 1;
104                     line.Y1 = point.Y - 1;
105                     line.X2 = line.X1;
106                     line.Y2 = line.Y1;
107                     canvas.Children.Add(line);
108                     imgc.Tag = line;
109                 }
110             }
111         }
112 
113         private void Button_Click(object sender, RoutedEventArgs e)
114         {
115             isPupilDistance = true;
116         }
117 
118         private void Button_Click_1(object sender, RoutedEventArgs e)
119         {
120             isPupilDistance = false;
121         }
122 
123         /// <summary>
124         /// 计算瞳距
125         /// </summary>
126         /// <param name="sender"></param>
127         /// <param name="e"></param>
128         private void Button_Click_2(object sender, RoutedEventArgs e)
129         {
130             var l1 = img1.Tag as Line;
131             var l2 = img2.Tag as Line;
132 
133             if (l1 == null || l2 == null)
134             {
135                 MessageBox.Show("请先 启用瞳距 ，再在图片上画线");
136                 return;
137             }
138 
139             //获取第一个图片的线
140             var length1 = Distance(new Point(l1.X1, l1.Y1), new Point(l1.X2, l1.Y2));
141 
142             //获取第二个图片的线
143             var length2 = Distance(new Point(l2.X1, l2.Y1), new Point(l2.X2, l2.Y2));
144 
145             //利用三角函数计算出以第一个图的线为基准，延长第二个图的线
146             var AC = Math.Abs(l2.X2 - l2.X1);
147             var BC = Math.Abs(l2.Y2 - l2.Y1);
148 
149             var jiaodu = Math.Atan(BC / AC);
150             var sinVal = Math.Sin(jiaodu);
151             var cosVal = Math.Cos(jiaodu);
152             var ac = cosVal * length1;
153             var bc = sinVal * length1;
154 
155             double xnew = 0, ynew = 0;
156             if (l2.X2 > l2.X1) xnew = ac + l2.X1;
157             else xnew = l2.X1 - ac;
158 
159             if (l2.Y2 > l2.Y1) ynew = l2.Y1 + bc;
160             else ynew = l2.Y1 - bc;
161 
162             l2.X2 = xnew;
163             l2.Y2 = ynew;
164 
165             var wnew = length1 / (length2 / img2.ActualWidth);
166             var hnew = length1 / (length2 / img2.ActualHeight);
167 
168             //以用户画的起点作为缩放中心
169             var x = (double)img2.GetValue(Canvas.LeftProperty);
170             var y = (double)img2.GetValue(Canvas.TopProperty);
171 
172             //起始点相对于图片的位置
173             var l2xToimg = l2.X1 - x;
174             var l2yToimg = l2.Y1 - y;
175 
176             //获取起始点相对于图片的新位置，缩放后
177             var l2xToimgnew = l2xToimg / img2.ActualWidth * wnew;
178             var l2yToimgnew = l2yToimg / img2.ActualHeight * hnew;
179 
180             img2.SetValue(Canvas.LeftProperty, l2.X1 - l2xToimgnew);
181             img2.SetValue(Canvas.TopProperty, l2.Y1 - l2yToimgnew);
182 
183             //缩放
184             img2.Width = wnew;
185             img2.Height = hnew;
186         }
187 
188         /// <summary>
189         /// 计算点位之间的距离
190         /// </summary>
191         /// <param name="p1"></param>
192         /// <param name="p2"></param>
193         /// <returns></returns>
194         private double Distance(Point p1, Point p2)
195         {
196             double result = 0;
197             result = Math.Sqrt((p1.X - p2.X) * (p1.X - p2.X) + (p1.Y - p2.Y) * (p1.Y - p2.Y));
198             return result;
199         }
200 
201         /// <summary>
202         /// 重置
203         /// </summary>
204         /// <param name="sender"></param>
205         /// <param name="e"></param>
206         private void Button_Click_3(object sender, RoutedEventArgs e)
207         {
208             List<Line> l = new List<Line>();
209             foreach (var item in canvas.Children)
210             {
211                 if (item is Line line)
212                 {
213                     l.Add(line);
214                 }
215             }
216 
217             l.ForEach(c => canvas.Children.Remove(c));
218 
219             img2.Width = size.Width;
220             img2.Height = size.Height;
221 
222             img2.SetValue(Canvas.LeftProperty, 380.0);
223             img2.SetValue(Canvas.TopProperty, 100.0);
224         }
225     }
226 }

看到这里，可以先揉揉眼睛，放松下...

全部代码已经贴上，下面是下载链接，有需要的朋友可以移步下载，欢迎点评，谢谢~

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