《C# GDI+ 破境之道》：第一境 GDI+基础 —— 第三节：画圆形

Posted 2021-03-08 Mike Cheers 的技术乐园

有了上一节画矩形的基础，画圆形就不要太轻松+EZ：）所以，本节在画边线及填充上，就不做过多的讲解了，关注一下画“随机椭圆”、“正圆”、“路径填充”的具体实现就好。与画矩形相比较，画椭圆与之完全一致，没有任何特别之处。

在画矩形时，我们使用：

• System.Drawing.Graphics.DrawRectangle(Brush brush, Rectangle rect);
• System.Drawing.Graphics.FillRectangle(Brush brush, Rectangle rect);

在画圆形时，我们使用：

• System.Drawing.Graphics.DrawEllipse(Brush brush, Rectangle rect);
• System.Drawing.Graphics.FillEllipse(Brush brush, Rectangle rect);

看到了吧，就换了个方法名，参数连名都没换：）

所以，了解了如何画矩形，画圆形就是自然掌握的了。

本节就不多费口舌重复了：

  1 namespace MikeWare.GdiPlus.Ellipses
  2 {
  3     using System;
  4     using System.Collections.Generic;
  5     using System.Drawing;
  6     using System.Drawing.Drawing2D;
  7     using System.Windows.Forms;
  8 
  9     public partial class FormDrawEllipses : Form
 10     {
 11         private Random random = null;
 12         private Color penColor = Color.Transparent;
 13 
 14         public FormDrawEllipses()
 15         {
 16             InitializeComponent();
 17             random = new Random(DateTime.Now.Millisecond);
 18             penColor = GetRandomColor();
 19         }
 20 
 21         private Point GetRandomPoint()
 22         {
 23             return new Point(random.Next(0, ClientRectangle.Width), random.Next(0, ClientRectangle.Height - pnlToolbox.Height));
 24         }
 25 
 26         private Rectangle GetRandomRectangle()
 27         {
 28             var pointA = GetRandomPoint();
 29             var pointB = GetRandomPoint();
 30 
 31             return new Rectangle(Math.Min(pointA.X, pointB.X)
 32                 , Math.Min(pointA.Y, pointB.Y)
 33                 , Math.Abs(pointA.X - pointB.X)
 34                 , Math.Abs(pointA.Y - pointB.Y));
 35         }
 36 
 37         private Color GetRandomColor()
 38         {
 39             return Color.FromArgb(random.Next(0, 256), random.Next(0, 256), random.Next(0, 256));
 40         }
 41 
 42         private void ShowInformation(string message)
 43         {
 44             lblInformation.Text = message;
 45         }
 46 
 47         private void btnChangePenColor_Click(object sender, EventArgs e)
 48         {
 49             if (colors.ShowDialog(this) == DialogResult.OK)
 50             {
 51                 penColor = colors.Color;
 52             }
 53         }
 54 
 55         private void btnSwitchDoubleBuffered_Click(object sender, EventArgs e)
 56         {
 57             DoubleBuffered = !DoubleBuffered;
 58 
 59             ShowInformation($"二级缓冲：{DoubleBuffered}。");
 60         }
 61 
 62         private void btnDrawRandomEllipse_Click(object sender, EventArgs e)
 63         {
 64             var rectangle = GetRandomRectangle();
 65 
 66             var style = (DashStyle)(random.Next(0, 6));
 67             var dashCaps = new List<int> { 0, 2, 3 };
 68             var dashCap = (DashCap)dashCaps[random.Next(0, 3)];
 69 
 70             using (var g = CreateGraphics())
 71             using (var pen = new Pen(penColor, 4f))
 72             using (var brush = new LinearGradientBrush(rectangle, Color.Red, Color.Blue, LinearGradientMode.ForwardDiagonal))
 73             {
 74                 g.Clear(SystemColors.AppWorkspace);
 75                 g.SmoothingMode = SmoothingMode.HighQuality;
 76                 pen.DashStyle = style;
 77                 pen.DashCap = dashCap;
 78                 g.DrawEllipse(pen, rectangle);
 79             }
 80 
 81             ShowInformation($"随机椭圆，{rectangle}，虚线冒：{dashCap.ToString()}，线条样式：{style.ToString()}。");
 82         }
 83 
 84         private void btnDrawRandomCircle_Click(object sender, EventArgs e)
 85         {
 86             var rectangle = GetRandomRectangle();
 87             var diameter = Math.Min(rectangle.Size.Width, rectangle.Size.Height);
 88             rectangle = new Rectangle(rectangle.Location, new Size(diameter, diameter));
 89 
 90             var style = (DashStyle)(random.Next(0, 6));
 91             var dashCaps = new List<int> { 0, 2, 3 };
 92             var dashCap = (DashCap)dashCaps[random.Next(0, 3)];
 93 
 94             using (var g = CreateGraphics())
 95             using (var pen = new Pen(penColor, 4f))
 96             using (var brush = new LinearGradientBrush(rectangle, Color.Red, Color.Blue, LinearGradientMode.ForwardDiagonal))
 97             {
 98                 g.Clear(SystemColors.AppWorkspace);
 99                 g.SmoothingMode = SmoothingMode.HighQuality;
100                 pen.DashStyle = style;
101                 pen.DashCap = dashCap;
102                 g.DrawEllipse(pen, rectangle);
103             }
104 
105             ShowInformation($"正圆，{rectangle}，虚线冒：{dashCap.ToString()}，线条样式：{style.ToString()}。");
106         }
107 
108         private void btnFillWithPathGradientBrush_Click(object sender, EventArgs e)
109         {
110             var rectangle = GetRandomRectangle();
111 
112             var wrapMode = (WrapMode)(random.Next(0, 5));
113 
114             //var points = new Point[] { GetRandomPoint(), GetRandomPoint(), GetRandomPoint(), GetRandomPoint(), GetRandomPoint() };
115             var points = new Point[] { GetRandomPoint(), GetRandomPoint(), GetRandomPoint() };
116 
117             using (var g = CreateGraphics())
118             using (var brush = new PathGradientBrush(points, wrapMode))
119             {
120                 g.Clear(SystemColors.AppWorkspace);
121                 g.SmoothingMode = SmoothingMode.HighQuality;
122                 g.DrawEllipse(Pens.LightGray, rectangle);
123                 g.FillEllipse(brush, rectangle);
124             }
125 
126             ShowInformation($"路径填充，{rectangle}，WrapMode：{wrapMode}。");
127         }
128     }
129 }

画圆 —— FormDrawEllipses

同样，一个窗体项目，窗体的布局风格与上一节的保持一致：

几个方法不细说，直接上几个效果图草草了事……

正圆就是一种特殊的椭圆，它的rectangle的宽与高相等；

随机路径填充也蛮有意思的，有的图画，我都想直接拿来做logo了：）

 

好了，画圆的部分，内容就这么多，按照惯例，那么我们就来利用现有的知识，再耍个花活，画个贼溜溜的眼珠：）

private int maxDistance = 0;    // 最大移动距离，用来衡量鼠标距离眼球中心位置的极限；以这个距离极限，来等比缩放眼球移动的距离；
private Rectangle leftEyeBorderRect = Rectangle.Empty   // 左眼眼眶
    , rightEyeBorderRect = Rectangle.Empty              // 右眼眼眶
    , leftEyeBackRect = Rectangle.Empty                 // 左眼兰眼球
    , rightEyeBackRect = Rectangle.Empty                // 右眼兰眼球
    , leftEyeFrontRect = Rectangle.Empty                // 左眼黑眼珠
    , rightEyeFrontRect = Rectangle.Empty;              // 右眼黑眼珠

定义几个私有变量

注释里说明了这几个变量的意义；

 1 private void btnDrawFollowMouseEyes_Click(object sender, EventArgs e)
 2 {
 3     var center = new Point(ClientRectangle.Width / 2, (ClientRectangle.Height - pnlToolbox.Height) / 2);
 4     leftEyeBorderRect = new Rectangle(center.X - 250, center.Y - 40, 200, 80);
 5     rightEyeBorderRect = new Rectangle(center.X + 50, center.Y - 40, 200, 80);
 6     maxDistance = ClientRectangle.Width < (ClientRectangle.Height - pnlToolbox.Height)
 7         ? center.X - 150 - ClientRectangle.X
 8         : center.Y - ClientRectangle.Y;
 9 
10     var style = (DashStyle)(random.Next(0, 6));
11     var dashCaps = new List<int> { 0, 2, 3 };
12     var dashCap = (DashCap)dashCaps[random.Next(0, 3)];
13 
14     using (var g = CreateGraphics())
15     using (var pen = new Pen(penColor, 2f))
16     using (var brush = new SolidBrush(penColor))
17     {
18         g.Clear(SystemColors.AppWorkspace);
19         g.SmoothingMode = SmoothingMode.HighQuality;
20         pen.DashStyle = style;
21         pen.DashCap = dashCap;
22         g.FillEllipse(SystemBrushes.ControlLight, leftEyeBorderRect);
23         g.DrawEllipse(pen, leftEyeBorderRect);
24         g.FillEllipse(SystemBrushes.ControlLight, rightEyeBorderRect);
25         g.DrawEllipse(pen, rightEyeBorderRect);
26     }
27 
28     FormDrawEllipses_MouseMove(null, new MouseEventArgs(MouseButtons.Left, 0, 0, 0, 0));
29 
30     ShowInformation($"贼溜溜的眼睛，跟随鼠标移动的眼睛示例。");
31 }

贼眼珠按钮事件 —— btnDrawFollowMouseEyes_Click

这个事件中，主要就是画出眼眶和填充眼白；

 1 private void FormDrawEllipses_MouseMove(object sender, MouseEventArgs e)
 2 {
 3     if (Rectangle.Empty.Equals(leftEyeBorderRect) || Rectangle.Empty.Equals(rightEyeBorderRect))
 4         return;
 5 
 6     using (var g = CreateGraphics())
 7     using (var pen = new Pen(penColor, 2f))
 8     using (var brush = new SolidBrush(penColor))
 9     {
10         if (Rectangle.Empty != leftEyeBackRect)
11             g.FillEllipse(SystemBrushes.ControlLight, leftEyeBackRect);
12         if (Rectangle.Empty != rightEyeBackRect)
13             g.FillEllipse(SystemBrushes.ControlLight, rightEyeBackRect);
14         leftEyeBackRect = CalcRect(leftEyeBorderRect, e.Location, maxDistance, 15, 25);
15         rightEyeBackRect = CalcRect(rightEyeBorderRect, e.Location, maxDistance, 15, 25);
16         leftEyeFrontRect = CalcRect(leftEyeBackRect, e.Location, maxDistance, 15, 5);
17         rightEyeFrontRect = CalcRect(rightEyeBackRect, e.Location, maxDistance, 15, 5);
18 
19         brush.Color = Color.Blue;
20         g.FillEllipse(brush, leftEyeBackRect);
21         g.FillEllipse(brush, rightEyeBackRect);
22 
23         brush.Color = Color.Black;
24         g.FillEllipse(brush, leftEyeFrontRect);
25         g.FillEllipse(brush, rightEyeFrontRect);
26 
27         g.Flush();
28     }
29 }

窗体的鼠标移动事件 —— FormDrawEllipses_MouseMove

这个事件里，首先就是将上一次兰眼球的范围填充成眼白的颜色，然后就是根据当前鼠标位置，重新计算兰眼球和黑眼珠的位置，然后进行填充。

这样就形成了一个动态效果了。

 1 private Rectangle CalcRect(Rectangle baseRect, Point mouseLocation, int maxDistance, int maxMoveDistance, int radius)
 2 {
 3     var baseCenter = Point.Add(baseRect.Location, new Size(baseRect.Width / 2, baseRect.Height / 2));
 4 
 5     var radian = Math.Atan2((mouseLocation.Y - baseCenter.Y), (mouseLocation.X - baseCenter.X));
 6 
 7     var mouseDistance = Math.Min(maxDistance, Math.Sqrt(Math.Pow(mouseLocation.X - baseCenter.X, 2) + Math.Pow(mouseLocation.Y - baseCenter.Y, 2)));
 8 
 9     var moveDistance = maxMoveDistance * (mouseDistance / maxDistance);
10 
11     var targetCenter = new Point((int)Math.Ceiling(moveDistance * Math.Cos(radian) + baseCenter.X), (int)Math.Ceiling(moveDistance * Math.Sin(radian)) + baseCenter.Y);
12 
13     return new Rectangle(targetCenter.X - radius, targetCenter.Y - radius, radius * 2, radius * 2);
14 }

辅助方法 —— 计算眼球和眼珠的矩形位置

OK，完活，收工。

 

喜欢本系列丛书的朋友,可以点击链接加入QQ交流群(994761602)【C# 破境之道】
方便各位在有疑问的时候可以及时给我个反馈。同时，也算是给各位志同道合的朋友提供一个交流的平台。
需要源码的童鞋，也可以在群文件中获取最新源代码。