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~