《C# GDI+ 破境之道》：第一境 GDI+基础 —— 第三节：画圆形
MikeCheers 人气:0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 }
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，我都想直接那类做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
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 }
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 }
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 }
OK，完活，收工。
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