《C# GDI+ 破境之道》：第一境 GDI+基础 —— 第二节：画矩形
MikeCheers 人气:0有了上一节画线的基础，画矩形的各种边线就特别好理解了，所以，本节在矩形边线上，就不做过多的讲解了，关注一下画“随机矩形”的具体实现就好。与画线相比较，画矩形稍微复杂的一点就是在于它多了很多填充的样式。接下来，我们就来细细品味一番。
同样，一个窗体项目，窗体的布局风格与上一节的保持一致：
1 namespace MikeWare.GdiPlus.Rectangles
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 FormDrawRectangles : Form
10 {
11 private Random random = null;
12 private Color penColor = Color.Transparent;
13
14 public FormDrawRectangles()
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($"二级缓冲：{DoubleBuffered}。");
60 }
61
62 private void btnDrawRandomRectangle_Click(object sender, EventArgs e)
63 {
64 var rectangle = GetRandomRectangle();
65
66 var style = (DashStyle)(random.Next(0, 6));
67 var dashCaps = new List<int> { 0, 2, 3 };
68 var dashCap = (DashCap)dashCaps[random.Next(0, 3)];
69
70 using (var g = CreateGraphics())
71 using (var pen = new Pen(penColor, 4f))
72 using (var brush = new LinearGradientBrush(rectangle, Color.Red, Color.Blue, LinearGradientMode.ForwardDiagonal))
73 {
74 g.Clear(SystemColors.AppWorkspace);
75 g.SmoothingMode = SmoothingMode.HighQuality;
76 pen.DashStyle = style;
77 pen.DashCap = dashCap;
78 g.DrawRectangle(pen, rectangle);
79 }
80
81 ShowInformation($"随机矩形，{rectangle}，虚线冒：{dashCap.ToString()}，线条样式：{style.ToString()}。");
82 }
83
84 ……
85 }
86 }
与上一节给出的窗体定义及辅助方法雷同，这里不做过多说明，增加了两个辅助方法，一个是获取随机矩形Rectangle GetRandomRectangle()，一个是获取随机颜色Color GetRandomColor()，相信什么是矩形和颜色，生物老师都教过：）而且本节的重点也不在边线的绘制上，其基本方法就是Graphics.DrawRectangle(Pen pen, Rectangle rect)，也直接给出了绘制“随机矩形”的代码，有了画线的基础，应该没什么问题了。
下面，重点来了：
1、绘制具有渐变色填充的矩形
1 private void btnFillLinearGradientColor_Click(object sender, EventArgs e)
2 {
3 var rectangle1 = GetRandomRectangle();
4 var rectangle2 = GetRandomRectangle();
5
6 var gradient = (LinearGradientMode)(random.Next(0, 4));
7 var angle = (random.Next(0, 361));
8
9 using (var g = CreateGraphics())
10 {
11 g.Clear(SystemColors.AppWorkspace);
12 g.SmoothingMode = SmoothingMode.HighQuality;
13 using (var brush = new LinearGradientBrush(rectangle1, GetRandomColor(), GetRandomColor(), gradient))
14 {
15 g.FillRectangle(brush, rectangle1);
16 }
17
18 using (var brush = new LinearGradientBrush(rectangle2, GetRandomColor(), GetRandomColor(), angle, 0 == angle % 2))
19 {
20 g.FillRectangle(brush, rectangle2);
21 }
22 }
23
24 ShowInformation($"渐变色填充，{rectangle1}，LinearGradient：{gradient}；{rectangle2}，Angle：{angle}。");
25 }
绘制渐变色填充，关键在于构造一个合适的LinearGradientBrush，然后调用Graphics.FillRectangle(Brush brush, Rectangle rect)就可以了。
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.LinearGradientBrush
// class with the specified points and colors.
//
// Parameters:
// point1:
// A System.Drawing.PointF structure that represents the starting point of the linear
// gradient.
//
// point2:
// A System.Drawing.PointF structure that represents the endpoint of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color of the linear
// gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color of the linear
// gradient.
public LinearGradientBrush(PointF point1, PointF point2, Color color1, Color color2);
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.LinearGradientBrush
// class with the specified points and colors.
//
// Parameters:
// point1:
// A System.Drawing.Point structure that represents the starting point of the linear
// gradient.
//
// point2:
// A System.Drawing.Point structure that represents the endpoint of the linear gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color of the linear
// gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color of the linear
// gradient.
public LinearGradientBrush(Point point1, Point point2, Color color1, Color color2);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush based
// on a rectangle, starting and ending colors, and an orientation mode.
//
// Parameters:
// rect:
// A System.Drawing.RectangleF structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// linearGradientMode:
// A System.Drawing.Drawing2D.LinearGradientMode enumeration element that specifies
// the orientation of the gradient. The orientation determines the starting and
// ending points of the gradient. For example, LinearGradientMode.ForwardDiagonal
// specifies that the starting point is the upper-left corner of the rectangle and
// the ending point is the lower-right corner of the rectangle.
public LinearGradientBrush(RectangleF rect, Color color1, Color color2, LinearGradientMode linearGradientMode);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush class
// based on a rectangle, starting and ending colors, and orientation.
//
// Parameters:
// rect:
// A System.Drawing.Rectangle structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// linearGradientMode:
// A System.Drawing.Drawing2D.LinearGradientMode enumeration element that specifies
// the orientation of the gradient. The orientation determines the starting and
// ending points of the gradient. For example, LinearGradientMode.ForwardDiagonal
// specifies that the starting point is the upper-left corner of the rectangle and
// the ending point is the lower-right corner of the rectangle.
public LinearGradientBrush(Rectangle rect, Color color1, Color color2, LinearGradientMode linearGradientMode);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush class
// based on a rectangle, starting and ending colors, and an orientation angle.
//
// Parameters:
// rect:
// A System.Drawing.RectangleF structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// angle:
// The angle, measured in degrees clockwise from the x-axis, of the gradient's orientation
// line.
public LinearGradientBrush(RectangleF rect, Color color1, Color color2, float angle);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush class
// based on a rectangle, starting and ending colors, and an orientation angle.
//
// Parameters:
// rect:
// A System.Drawing.Rectangle structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// angle:
// The angle, measured in degrees clockwise from the x-axis, of the gradient's orientation
// line.
public LinearGradientBrush(Rectangle rect, Color color1, Color color2, float angle);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush class
// based on a rectangle, starting and ending colors, and an orientation angle.
//
// Parameters:
// rect:
// A System.Drawing.RectangleF structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// angle:
// The angle, measured in degrees clockwise from the x-axis, of the gradient's orientation
// line.
//
// isAngleScaleable:
// Set to true to specify that the angle is affected by the transform associated
// with this System.Drawing.Drawing2D.LinearGradientBrush; otherwise, false.
public LinearGradientBrush(RectangleF rect, Color color1, Color color2, float angle, bool isAngleScaleable);
//
// Summary:
// Creates a new instance of the System.Drawing.Drawing2D.LinearGradientBrush class
// based on a rectangle, starting and ending colors, and an orientation angle.
//
// Parameters:
// rect:
// A System.Drawing.Rectangle structure that specifies the bounds of the linear
// gradient.
//
// color1:
// A System.Drawing.Color structure that represents the starting color for the gradient.
//
// color2:
// A System.Drawing.Color structure that represents the ending color for the gradient.
//
// angle:
// The angle, measured in degrees clockwise from the x-axis, of the gradient's orientation
// line.
//
// isAngleScaleable:
// Set to true to specify that the angle is affected by the transform associated
// with this System.Drawing.Drawing2D.LinearGradientBrush; otherwise, false.
public LinearGradientBrush(Rectangle rect, Color color1, Color color2, float angle, bool isAngleScaleable);
从LinearGradientBrush的一系列构造函数可以看出，LinearGradientBrush意在指出完成从一种颜色渐变到另一种颜色的渐变周期。
这里我们着重说一下LinearGradientBrush的第一个参数，无论是一个Rectangle还是两个Point，他们描述的是渐变色完成的区间。为了理解和描述上的方便，我们假设绘制的是一个水平方向的渐变，
这个时候，渐变区间与我们要填充的矩形并没有交集，我们可以这样理解，这个渐变区间会以定义的区域为原点，向四周扩散，
然后在填充的时候，只保留了我们要填充的矩形区域可见，
OK，假设我已经把这个关系说清楚了：）在有就是LinearGradientMode这个枚举，
//
// Summary:
// Specifies the direction of a linear gradient.
public enum LinearGradientMode
{
//
// Summary:
// Specifies a gradient from left to right.
Horizontal = 0,
//
// Summary:
// Specifies a gradient from top to bottom.
Vertical = 1,
//
// Summary:
// Specifies a gradient from upper left to lower right.
ForwardDiagonal = 2,
//
// Summary:
// Specifies a gradient from upper right to lower left.
BackwardDiagonal = 3
}
它列举了从第一种颜色过渡到第二种颜色的方向，从左到右，从上到下，从左上到右下，从右上到左下四个比较正规的方向；
关于LinearGradientBrush的另一个参数(float angle)，它用来指示颜色过渡的方向，结合LinearGradientMode理解，同时，指出，angle可以为负数，下图帮助理解一下GDI+中的angle：
LinearGradientBrush类还有一些非常有用的属性和方法，可以帮助完成一些更为复杂的任务，这里就不细说了，又需要的童鞋可以深入研究一下：）
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.ColorBlend that defines a multicolor
// linear gradient.
//
// Returns:
// A System.Drawing.Drawing2D.ColorBlend that defines a multicolor linear gradient.
public ColorBlend InterpolationColors { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.Blend that specifies positions and factors
// that define a custom falloff for the gradient.
//
// Returns:
// A System.Drawing.Drawing2D.Blend that represents a custom falloff for the gradient.
public Blend Blend { get; set; }
//
// Summary:
// Gets or sets a value indicating whether gamma correction is enabled for this
// System.Drawing.Drawing2D.LinearGradientBrush.
//
// Returns:
// The value is true if gamma correction is enabled for this System.Drawing.Drawing2D.LinearGradientBrush;
// otherwise, false.
public bool GammaCorrection { get; set; }
//
// Summary:
// Gets a rectangular region that defines the starting and ending points of the
// gradient.
//
// Returns:
// A System.Drawing.RectangleF structure that specifies the starting and ending
// points of the gradient.
public RectangleF Rectangle { get; }
//
// Summary:
// Gets or sets the starting and ending colors of the gradient.
//
// Returns:
// An array of two System.Drawing.Color structures that represents the starting
// and ending colors of the gradient.
public Color[] LinearColors { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.WrapMode enumeration that indicates the
// wrap mode for this System.Drawing.Drawing2D.LinearGradientBrush.
//
// Returns:
// A System.Drawing.Drawing2D.WrapMode that specifies how fills drawn with this
// System.Drawing.Drawing2D.LinearGradientBrush are tiled.
public WrapMode WrapMode { get; set; }
//
// Summary:
// Gets or sets a copy System.Drawing.Drawing2D.Matrix that defines a local geometric
// transform for this System.Drawing.Drawing2D.LinearGradientBrush.
//
// Returns:
// A copy of the System.Drawing.Drawing2D.Matrix that defines a geometric transform
// that applies only to fills drawn with this System.Drawing.Drawing2D.LinearGradientBrush.
public Matrix Transform { get; set; }
//
// Summary:
// Creates an exact copy of this System.Drawing.Drawing2D.LinearGradientBrush.
//
// Returns:
// The System.Drawing.Drawing2D.LinearGradientBrush this method creates, cast as
// an object.
public override object Clone();
//
// Summary:
// Multiplies the System.Drawing.Drawing2D.Matrix that represents the local geometric
// transform of this System.Drawing.Drawing2D.LinearGradientBrush by the specified
// System.Drawing.Drawing2D.Matrix in the specified order.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix by which to multiply the geometric transform.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies in which order to multiply
// the two matrices.
public void MultiplyTransform(Matrix matrix, MatrixOrder order);
//
// Summary:
// Multiplies the System.Drawing.Drawing2D.Matrix that represents the local geometric
// transform of this System.Drawing.Drawing2D.LinearGradientBrush by the specified
// System.Drawing.Drawing2D.Matrix by prepending the specified System.Drawing.Drawing2D.Matrix.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix by which to multiply the geometric transform.
public void MultiplyTransform(Matrix matrix);
//
// Summary:
// Resets the System.Drawing.Drawing2D.LinearGradientBrush.Transform property to
// identity.
public void ResetTransform();
//
// Summary:
// Rotates the local geometric transform by the specified amount. This method prepends
// the rotation to the transform.
//
// Parameters:
// angle:
// The angle of rotation.
public void RotateTransform(float angle);
//
// Summary:
// Rotates the local geometric transform by the specified amount in the specified
// order.
//
// Parameters:
// angle:
// The angle of rotation.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies whether to append or prepend
// the rotation matrix.
public void RotateTransform(float angle, MatrixOrder order);
//
// Summary:
// Scales the local geometric transform by the specified amounts. This method prepends
// the scaling matrix to the transform.
//
// Parameters:
// sx:
// The amount by which to scale the transform in the x-axis direction.
//
// sy:
// The amount by which to scale the transform in the y-axis direction.
public void ScaleTransform(float sx, float sy);
//
// Summary:
// Scales the local geometric transform by the specified amounts in the specified
// order.
//
// Parameters:
// sx:
// The amount by which to scale the transform in the x-axis direction.
//
// sy:
// The amount by which to scale the transform in the y-axis direction.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies whether to append or prepend
// the scaling matrix.
public void ScaleTransform(float sx, float sy, MatrixOrder order);
//
// Summary:
// Creates a linear gradient with a center color and a linear falloff to a single
// color on both ends.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies the center of the gradient (the point
// where the gradient is composed of only the ending color).
//
// scale:
// A value from 0 through1 that specifies how fast the colors falloff from the starting
// color to focus (ending color)
public void SetBlendTriangularShape(float focus, float scale);
//
// Summary:
// Creates a linear gradient with a center color and a linear falloff to a single
// color on both ends.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies the center of the gradient (the point
// where the gradient is composed of only the ending color).
public void SetBlendTriangularShape(float focus);
//
// Summary:
// Creates a gradient falloff based on a bell-shaped curve.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies the center of the gradient (the point
// where the gradient is composed of only the ending color).
//
// scale:
// A value from 0 through 1 that specifies how fast the colors falloff from the
// focus.
public void SetSigmaBellShape(float focus, float scale);
//
// Summary:
// Creates a gradient falloff based on a bell-shaped curve.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies the center of the gradient (the point
// where the starting color and ending color are blended equally).
public void SetSigmaBellShape(float focus);
//
// Summary:
// Translates the local geometric transform by the specified dimensions. This method
// prepends the translation to the transform.
//
// Parameters:
// dx:
// The value of the translation in x.
//
// dy:
// The value of the translation in y.
public void TranslateTransform(float dx, float dy);
//
// Summary:
// Translates the local geometric transform by the specified dimensions in the specified
// order.
//
// Parameters:
// dx:
// The value of the translation in x.
//
// dy:
// The value of the translation in y.
//
// order:
// The order (prepend or append) in which to apply the translation.
public void TranslateTransform(float dx, float dy, MatrixOrder order);
2、绘制系统画刷填充矩形
1 private void btnFillWithSystemBrushes_Click(object sender, EventArgs e)
2 {
3 var rectangle = GetRandomRectangle();
4
5 var systemBrushes = new List<Brush> {
6 SystemBrushes.GradientInactiveCaption ,
7 SystemBrushes.Window ,
8 SystemBrushes.ScrollBar ,
9 SystemBrushes.MenuText ,
10 SystemBrushes.MenuHighlight ,
11 SystemBrushes.MenuBar ,
12 SystemBrushes.Menu ,
13 SystemBrushes.InfoText ,
14 SystemBrushes.Info ,
15 SystemBrushes.InactiveCaptionText ,
16 SystemBrushes.InactiveBorder ,
17 SystemBrushes.InactiveCaption ,
18 SystemBrushes.HotTrack ,
19 SystemBrushes.HighlightText ,
20 SystemBrushes.Highlight ,
21 SystemBrushes.GrayText ,
22 SystemBrushes.WindowText ,
23 SystemBrushes.GradientActiveCaption ,
24 SystemBrushes.ActiveBorder ,
25 SystemBrushes.ActiveCaption ,
26 SystemBrushes.ActiveCaptionText ,
27 SystemBrushes.AppWorkspace ,
28 SystemBrushes.ButtonFace ,
29 SystemBrushes.ButtonHighlight ,
30 SystemBrushes.WindowFrame ,
31 SystemBrushes.ButtonShadow ,
32 SystemBrushes.ControlLightLight ,
33 SystemBrushes.ControlLight ,
34 SystemBrushes.ControlDark ,
35 SystemBrushes.ControlDarkDark ,
36 SystemBrushes.ControlText ,
37 SystemBrushes.Desktop ,
38 SystemBrushes.Control ,};
39
40 var brush = systemBrushes[random.Next(0, systemBrushes.Count)];
41
42 using (var g = CreateGraphics())
43 {
44 g.Clear(SystemColors.AppWorkspace);
45 g.SmoothingMode = SmoothingMode.HighQuality;
46 g.FillRectangle(brush, rectangle);
47 }
48
49 ShowInformation($"画刷填充，{rectangle}，画刷名称：{(brush as SolidBrush)?.Color.Name}。");
50 }
本示例取用系统画刷SystemBrushes来作为填充，其实就是Windows系统的一些画刷配置，比如桌面背景色、按钮颜色等。除非制作自定义控件或组件，否则，其它场景可能很少应用。不过，这个示例也同样适用于SolidBrush，就是纯色画刷。没什么特表之处，一笔带过吧。
3、绘制镶嵌填充矩形
1 private void btnFillWithHatchBrush_Click(object sender, EventArgs e)
2 {
3 var rectangle = GetRandomRectangle();
4
5 var style = (HatchStyle)(random.Next(0, 53));
6 var foreColor = GetRandomColor();
7 var backColor = GetRandomColor();
8
9 using (var g = CreateGraphics())
10 using (var brush = new HatchBrush(style, foreColor, backColor))
11 {
12 g.Clear(SystemColors.AppWorkspace);
13 g.SmoothingMode = SmoothingMode.HighQuality;
14 g.FillRectangle(brush, rectangle);
15 }
16
17 ShowInformation($"镶嵌填充，{rectangle}，前景色：{foreColor}，背景色：{backColor}，填充样式：{style.ToString()}。");
18 }
System.Drawing.Drawing2D.HatchBrush是一个比较有意思的画刷，它根据两种颜色和不同的镶嵌样式，组合出各种不同的图案，比较适合作为场景的背景，建议多玩儿玩儿。
技术上没什么特别点，主要是支持的样式比较多，就不一一介绍了。
namespace System.Drawing.Drawing2D
{
//
// Summary:
// Specifies the different patterns available for System.Drawing.Drawing2D.HatchBrush
// objects.
public enum HatchStyle
{
//
// Summary:
// A pattern of horizontal lines.
Horizontal = 0,
//
// Summary:
// Specifies hatch style System.Drawing.Drawing2D.HatchStyle.Horizontal.
Min = 0,
//
// Summary:
// A pattern of vertical lines.
Vertical = 1,
//
// Summary:
// A pattern of lines on a diagonal from upper left to lower right.
ForwardDiagonal = 2,
//
// Summary:
// A pattern of lines on a diagonal from upper right to lower left.
BackwardDiagonal = 3,
//
// Summary:
// Specifies horizontal and vertical lines that cross.
Cross = 4,
//
// Summary:
// Specifies the hatch style System.Drawing.Drawing2D.HatchStyle.Cross.
LargeGrid = 4,
//
// Summary:
// Specifies hatch style System.Drawing.Drawing2D.HatchStyle.SolidDiamond.
Max = 4,
//
// Summary:
// A pattern of crisscross diagonal lines.
DiagonalCross = 5,
//
// Summary:
// Specifies a 5-percent hatch. The ratio of foreground color to background color
// is 5:95.
Percent05 = 6,
//
// Summary:
// Specifies a 10-percent hatch. The ratio of foreground color to background color
// is 10:90.
Percent10 = 7,
//
// Summary:
// Specifies a 20-percent hatch. The ratio of foreground color to background color
// is 20:80.
Percent20 = 8,
//
// Summary:
// Specifies a 25-percent hatch. The ratio of foreground color to background color
// is 25:75.
Percent25 = 9,
//
// Summary:
// Specifies a 30-percent hatch. The ratio of foreground color to background color
// is 30:70.
Percent30 = 10,
//
// Summary:
// Specifies a 40-percent hatch. The ratio of foreground color to background color
// is 40:60.
Percent40 = 11,
//
// Summary:
// Specifies a 50-percent hatch. The ratio of foreground color to background color
// is 50:50.
Percent50 = 12,
//
// Summary:
// Specifies a 60-percent hatch. The ratio of foreground color to background color
// is 60:40.
Percent60 = 13,
//
// Summary:
// Specifies a 70-percent hatch. The ratio of foreground color to background color
// is 70:30.
Percent70 = 14,
//
// Summary:
// Specifies a 75-percent hatch. The ratio of foreground color to background color
// is 75:25.
Percent75 = 15,
//
// Summary:
// Specifies a 80-percent hatch. The ratio of foreground color to background color
// is 80:100.
Percent80 = 16,
//
// Summary:
// Specifies a 90-percent hatch. The ratio of foreground color to background color
// is 90:10.
Percent90 = 17,
//
// Summary:
// Specifies diagonal lines that slant to the right from top points to bottom points
// and are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.ForwardDiagonal,
// but are not antialiased.
LightDownwardDiagonal = 18,
//
// Summary:
// Specifies diagonal lines that slant to the left from top points to bottom points
// and are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.BackwardDiagonal,
// but they are not antialiased.
LightUpwardDiagonal = 19,
//
// Summary:
// Specifies diagonal lines that slant to the right from top points to bottom points,
// are spaced 50 percent closer together than, and are twice the width of System.Drawing.Drawing2D.HatchStyle.ForwardDiagonal.
// This hatch pattern is not antialiased.
DarkDownwardDiagonal = 20,
//
// Summary:
// Specifies diagonal lines that slant to the left from top points to bottom points,
// are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.BackwardDiagonal,
// and are twice its width, but the lines are not antialiased.
DarkUpwardDiagonal = 21,
//
// Summary:
// Specifies diagonal lines that slant to the right from top points to bottom points,
// have the same spacing as hatch style System.Drawing.Drawing2D.HatchStyle.ForwardDiagonal,
// and are triple its width, but are not antialiased.
WideDownwardDiagonal = 22,
//
// Summary:
// Specifies diagonal lines that slant to the left from top points to bottom points,
// have the same spacing as hatch style System.Drawing.Drawing2D.HatchStyle.BackwardDiagonal,
// and are triple its width, but are not antialiased.
WideUpwardDiagonal = 23,
//
// Summary:
// Specifies vertical lines that are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.Vertical.
LightVertical = 24,
//
// Summary:
// Specifies horizontal lines that are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.Horizontal.
LightHorizontal = 25,
//
// Summary:
// Specifies vertical lines that are spaced 75 percent closer together than hatch
// style System.Drawing.Drawing2D.HatchStyle.Vertical (or 25 percent closer together
// than System.Drawing.Drawing2D.HatchStyle.LightVertical).
NarrowVertical = 26,
//
// Summary:
// Specifies horizontal lines that are spaced 75 percent closer together than hatch
// style System.Drawing.Drawing2D.HatchStyle.Horizontal (or 25 percent closer together
// than System.Drawing.Drawing2D.HatchStyle.LightHorizontal).
NarrowHorizontal = 27,
//
// Summary:
// Specifies vertical lines that are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.Vertical
// and are twice its width.
DarkVertical = 28,
//
// Summary:
// Specifies horizontal lines that are spaced 50 percent closer together than System.Drawing.Drawing2D.HatchStyle.Horizontal
// and are twice the width of System.Drawing.Drawing2D.HatchStyle.Horizontal.
DarkHorizontal = 29,
//
// Summary:
// Specifies dashed diagonal lines, that slant to the right from top points to bottom
// points.
DashedDownwardDiagonal = 30,
//
// Summary:
// Specifies dashed diagonal lines, that slant to the left from top points to bottom
// points.
DashedUpwardDiagonal = 31,
//
// Summary:
// Specifies dashed horizontal lines.
DashedHorizontal = 32,
//
// Summary:
// Specifies dashed vertical lines.
DashedVertical = 33,
//
// Summary:
// Specifies a hatch that has the appearance of confetti.
SmallConfetti = 34,
//
// Summary:
// Specifies a hatch that has the appearance of confetti, and is composed of larger
// pieces than System.Drawing.Drawing2D.HatchStyle.SmallConfetti.
LargeConfetti = 35,
//
// Summary:
// Specifies horizontal lines that are composed of zigzags.
ZigZag = 36,
//
// Summary:
// Specifies horizontal lines that are composed of tildes.
Wave = 37,
//
// Summary:
// Specifies a hatch that has the appearance of layered bricks that slant to the
// left from top points to bottom points.
DiagonalBrick = 38,
//
// Summary:
// Specifies a hatch that has the appearance of horizontally layered bricks.
HorizontalBrick = 39,
//
// Summary:
// Specifies a hatch that has the appearance of a woven material.
Weave = 40,
//
// Summary:
// Specifies a hatch that has the appearance of a plaid material.
Plaid = 41,
//
// Summary:
// Specifies a hatch that has the appearance of divots.
Divot = 42,
//
// Summary:
// Specifies horizontal and vertical lines, each of which is composed of dots, that
// cross.
DottedGrid = 43,
//
// Summary:
// Specifies forward diagonal and backward diagonal lines, each of which is composed
// of dots, that cross.
DottedDiamond = 44,
//
// Summary:
// Specifies a hatch that has the appearance of diagonally layered shingles that
// slant to the right from top points to bottom points.
Shingle = 45,
//
// Summary:
// Specifies a hatch that has the appearance of a trellis.
Trellis = 46,
//
// Summary:
// Specifies a hatch that has the appearance of spheres laid adjacent to one another.
Sphere = 47,
//
// Summary:
// Specifies horizontal and vertical lines that cross and are spaced 50 percent
// closer together than hatch style System.Drawing.Drawing2D.HatchStyle.Cross.
SmallGrid = 48,
//
// Summary:
// Specifies a hatch that has the appearance of a checkerboard.
SmallCheckerBoard = 49,
//
// Summary:
// Specifies a hatch that has the appearance of a checkerboard with squares that
// are twice the size of System.Drawing.Drawing2D.HatchStyle.SmallCheckerBoard.
LargeCheckerBoard = 50,
//
// Summary:
// Specifies forward diagonal and backward diagonal lines that cross but are not
// antialiased.
OutlinedDiamond = 51,
//
// Summary:
// Specifies a hatch that has the appearance of a checkerboard placed diagonally.
SolidDiamond = 52
}
}
4、绘制纹理填充矩形
1 private void btnFillWithTextureBrush_Click(object sender, EventArgs e)
2 {
3 var rectangle = GetRandomRectangle();
4
5 var wrapMode = (WrapMode)(random.Next(0, 5));
6
7 var image = Icon.ToBitmap();
8
9 using (var g = CreateGraphics())
10 using (var brush = new TextureBrush(image, wrapMode))
11 {
12 g.Clear(SystemColors.AppWorkspace);
13 g.SmoothingMode = SmoothingMode.HighQuality;
14 g.FillRectangle(brush, rectangle);
15 }
16
17 ShowInformation($"纹理填充，{rectangle}，WrapMode：{wrapMode}。");
18 }
纹理填充的关键在于对System.Drawing.TextureBrush这个画刷以及System.Drawing.Drawing2D.WrapMode的使用，
namespace System.Drawing
{
//
// Summary:
// Each property of the System.Drawing.TextureBrush class is a System.Drawing.Brush
// object that uses an image to fill the interior of a shape. This class cannot
// be inherited.
public sealed class TextureBrush : Brush
{
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image.
//
// Parameters:
// bitmap:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
public TextureBrush(Image bitmap);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image and wrap mode.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// wrapMode:
// A System.Drawing.Drawing2D.WrapMode enumeration that specifies how this System.Drawing.TextureBrush
// object is tiled.
public TextureBrush(Image image, WrapMode wrapMode);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image and bounding rectangle.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// dstRect:
// A System.Drawing.RectangleF structure that represents the bounding rectangle
// for this System.Drawing.TextureBrush object.
public TextureBrush(Image image, RectangleF dstRect);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image and bounding rectangle.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// dstRect:
// A System.Drawing.Rectangle structure that represents the bounding rectangle for
// this System.Drawing.TextureBrush object.
public TextureBrush(Image image, Rectangle dstRect);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image, wrap mode, and bounding rectangle.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// wrapMode:
// A System.Drawing.Drawing2D.WrapMode enumeration that specifies how this System.Drawing.TextureBrush
// object is tiled.
//
// dstRect:
// A System.Drawing.RectangleF structure that represents the bounding rectangle
// for this System.Drawing.TextureBrush object.
public TextureBrush(Image image, WrapMode wrapMode, RectangleF dstRect);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image, wrap mode, and bounding rectangle.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// wrapMode:
// A System.Drawing.Drawing2D.WrapMode enumeration that specifies how this System.Drawing.TextureBrush
// object is tiled.
//
// dstRect:
// A System.Drawing.Rectangle structure that represents the bounding rectangle for
// this System.Drawing.TextureBrush object.
public TextureBrush(Image image, WrapMode wrapMode, Rectangle dstRect);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image, bounding rectangle, and image attributes.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// dstRect:
// A System.Drawing.RectangleF structure that represents the bounding rectangle
// for this System.Drawing.TextureBrush object.
//
// imageAttr:
// An System.Drawing.Imaging.ImageAttributes object that contains additional information
// about the image used by this System.Drawing.TextureBrush object.
public TextureBrush(Image image, RectangleF dstRect, ImageAttributes imageAttr);
//
// Summary:
// Initializes a new System.Drawing.TextureBrush object that uses the specified
// image, bounding rectangle, and image attributes.
//
// Parameters:
// image:
// The System.Drawing.Image object with which this System.Drawing.TextureBrush object
// fills interiors.
//
// dstRect:
// A System.Drawing.Rectangle structure that represents the bounding rectangle for
// this System.Drawing.TextureBrush object.
//
// imageAttr:
// An System.Drawing.Imaging.ImageAttributes object that contains additional information
// about the image used by this System.Drawing.TextureBrush object.
public TextureBrush(Image image, Rectangle dstRect, ImageAttributes imageAttr);
//
// Summary:
// Gets or sets a copy of the System.Drawing.Drawing2D.Matrix object that defines
// a local geometric transformation for the image associated with this System.Drawing.TextureBrush
// object.
//
// Returns:
// A copy of the System.Drawing.Drawing2D.Matrix object that defines a geometric
// transformation that applies only to fills drawn by using this System.Drawing.TextureBrush
// object.
public Matrix Transform { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.WrapMode enumeration that indicates the
// wrap mode for this System.Drawing.TextureBrush object.
//
// Returns:
// A System.Drawing.Drawing2D.WrapMode enumeration that specifies how fills drawn
// by using this System.Drawing.Drawing2D.LinearGradientBrush object are tiled.
public WrapMode WrapMode { get; set; }
//
// Summary:
// Gets the System.Drawing.Image object associated with this System.Drawing.TextureBrush
// object.
//
// Returns:
// An System.Drawing.Image object that represents the image with which this System.Drawing.TextureBrush
// object fills shapes.
public Image Image { get; }
//
// Summary:
// Creates an exact copy of this System.Drawing.TextureBrush object.
//
// Returns:
// The System.Drawing.TextureBrush object this method creates, cast as an System.Object
// object.
public override object Clone();
//
// Summary:
// Multiplies the System.Drawing.Drawing2D.Matrix object that represents the local
// geometric transformation of this System.Drawing.TextureBrush object by the specified
// System.Drawing.Drawing2D.Matrix object in the specified order.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix object by which to multiply the geometric
// transformation.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder enumeration that specifies the order in
// which to multiply the two matrices.
public void MultiplyTransform(Matrix matrix, MatrixOrder order);
//
// Summary:
// Multiplies the System.Drawing.Drawing2D.Matrix object that represents the local
// geometric transformation of this System.Drawing.TextureBrush object by the specified
// System.Drawing.Drawing2D.Matrix object by prepending the specified System.Drawing.Drawing2D.Matrix
// object.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix object by which to multiply the geometric
// transformation.
public void MultiplyTransform(Matrix matrix);
//
// Summary:
// Resets the Transform property of this System.Drawing.TextureBrush object to identity.
public void ResetTransform();
//
// Summary:
// Rotates the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified amount. This method prepends the rotation to the transformation.
//
// Parameters:
// angle:
// The angle of rotation.
public void RotateTransform(float angle);
//
// Summary:
// Rotates the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified amount in the specified order.
//
// Parameters:
// angle:
// The angle of rotation.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder enumeration that specifies whether to
// append or prepend the rotation matrix.
public void RotateTransform(float angle, MatrixOrder order);
//
// Summary:
// Scales the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified amounts. This method prepends the scaling matrix to the
// transformation.
//
// Parameters:
// sx:
// The amount by which to scale the transformation in the x direction.
//
// sy:
// The amount by which to scale the transformation in the y direction.
public void ScaleTransform(float sx, float sy);
//
// Summary:
// Scales the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified amounts in the specified order.
//
// Parameters:
// sx:
// The amount by which to scale the transformation in the x direction.
//
// sy:
// The amount by which to scale the transformation in the y direction.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder enumeration that specifies whether to
// append or prepend the scaling matrix.
public void ScaleTransform(float sx, float sy, MatrixOrder order);
//
// Summary:
// Translates the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified dimensions. This method prepends the translation to the
// transformation.
//
// Parameters:
// dx:
// The dimension by which to translate the transformation in the x direction.
//
// dy:
// The dimension by which to translate the transformation in the y direction.
public void TranslateTransform(float dx, float dy);
//
// Summary:
// Translates the local geometric transformation of this System.Drawing.TextureBrush
// object by the specified dimensions in the specified order.
//
// Parameters:
// dx:
// The dimension by which to translate the transformation in the x direction.
//
// dy:
// The dimension by which to translate the transformation in the y direction.
//
// order:
// The order (prepend or append) in which to apply the translation.
public void TranslateTransform(float dx, float dy, MatrixOrder order);
}
}
namespace System.Drawing.Drawing2D
{
//
// Summary:
// Specifies how a texture or gradient is tiled when it is smaller than the area
// being filled.
public enum WrapMode
{
//
// Summary:
// Tiles the gradient or texture.
Tile = 0,
//
// Summary:
// Reverses the texture or gradient horizontally and then tiles the texture or gradient.
TileFlipX = 1,
//
// Summary:
// Reverses the texture or gradient vertically and then tiles the texture or gradient.
TileFlipY = 2,
//
// Summary:
// Reverses the texture or gradient horizontally and vertically and then tiles the
// texture or gradient.
TileFlipXY = 3,
//
// Summary:
// The texture or gradient is not tiled.
Clamp = 4
}
}
TextureBrush这个画刷的主要成分是Image，由于我们还没接触Image，这里就简单实现一下使用范例，等以后对Image有足够的了解，这个画刷也就非常简单了。本示例就简单的将窗体的Icon作为Image使用了。
5、绘制路径过渡填充矩形
1 private void btnFillWithPathGradientBrush_Click(object sender, EventArgs e)
2 {
3 var rectangle = GetRandomRectangle();
4
5 var wrapMode = (WrapMode)(random.Next(0, 5));
6
7 var points = new Point[] { GetRandomPoint(), GetRandomPoint(), GetRandomPoint(), GetRandomPoint(), GetRandomPoint() };
8
9 using (var g = CreateGraphics())
10 using (var pen = new Pen(penColor, 2f))
11 using (var brush = new PathGradientBrush(points, wrapMode))
12 {
13 g.Clear(SystemColors.AppWorkspace);
14 g.SmoothingMode = SmoothingMode.HighQuality;
15 g.DrawRectangle(pen, rectangle);
16 g.FillRectangle(brush, rectangle);
17 }
18
19 ShowInformation($"路径填充，{rectangle}，WrapMode：{wrapMode}。");
20 }
路径过渡填充的关键在于对System.Drawing.Drawing2D.PathGradientBrush的使用以及与纹理填充一样的WrapMode。
namespace System.Drawing.Drawing2D
{
//
// Summary:
// Encapsulates a System.Drawing.Brush object that fills the interior of a System.Drawing.Drawing2D.GraphicsPath
// object with a gradient. This class cannot be inherited.
public sealed class PathGradientBrush : Brush
{
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.PathGradientBrush
// class with the specified points.
//
// Parameters:
// points:
// An array of System.Drawing.PointF structures that represents the points that
// make up the vertices of the path.
public PathGradientBrush(PointF[] points);
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.PathGradientBrush
// class with the specified points.
//
// Parameters:
// points:
// An array of System.Drawing.Point structures that represents the points that make
// up the vertices of the path.
public PathGradientBrush(Point[] points);
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.PathGradientBrush
// class with the specified path.
//
// Parameters:
// path:
// The System.Drawing.Drawing2D.GraphicsPath that defines the area filled by this
// System.Drawing.Drawing2D.PathGradientBrush.
public PathGradientBrush(GraphicsPath path);
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.PathGradientBrush
// class with the specified points and wrap mode.
//
// Parameters:
// points:
// An array of System.Drawing.PointF structures that represents the points that
// make up the vertices of the path.
//
// wrapMode:
// A System.Drawing.Drawing2D.WrapMode that specifies how fills drawn with this
// System.Drawing.Drawing2D.PathGradientBrush are tiled.
public PathGradientBrush(PointF[] points, WrapMode wrapMode);
//
// Summary:
// Initializes a new instance of the System.Drawing.Drawing2D.PathGradientBrush
// class with the specified points and wrap mode.
//
// Parameters:
// points:
// An array of System.Drawing.Point structures that represents the points that make
// up the vertices of the path.
//
// wrapMode:
// A System.Drawing.Drawing2D.WrapMode that specifies how fills drawn with this
// System.Drawing.Drawing2D.PathGradientBrush are tiled.
public PathGradientBrush(Point[] points, WrapMode wrapMode);
//
// Summary:
// Gets or sets a copy of the System.Drawing.Drawing2D.Matrix that defines a local
// geometric transform for this System.Drawing.Drawing2D.PathGradientBrush.
//
// Returns:
// A copy of the System.Drawing.Drawing2D.Matrix that defines a geometric transform
// that applies only to fills drawn with this System.Drawing.Drawing2D.PathGradientBrush.
public Matrix Transform { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.ColorBlend that defines a multicolor
// linear gradient.
//
// Returns:
// A System.Drawing.Drawing2D.ColorBlend that defines a multicolor linear gradient.
public ColorBlend InterpolationColors { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.Blend that specifies positions and factors
// that define a custom falloff for the gradient.
//
// Returns:
// A System.Drawing.Drawing2D.Blend that represents a custom falloff for the gradient.
public Blend Blend { get; set; }
//
// Summary:
// Gets a bounding rectangle for this System.Drawing.Drawing2D.PathGradientBrush.
//
// Returns:
// A System.Drawing.RectangleF that represents a rectangular region that bounds
// the path this System.Drawing.Drawing2D.PathGradientBrush fills.
public RectangleF Rectangle { get; }
//
// Summary:
// Gets or sets the center point of the path gradient.
//
// Returns:
// A System.Drawing.PointF that represents the center point of the path gradient.
public PointF CenterPoint { get; set; }
//
// Summary:
// Gets or sets an array of colors that correspond to the points in the path this
// System.Drawing.Drawing2D.PathGradientBrush fills.
//
// Returns:
// An array of System.Drawing.Color structures that represents the colors associated
// with each point in the path this System.Drawing.Drawing2D.PathGradientBrush fills.
public Color[] SurroundColors { get; set; }
//
// Summary:
// Gets or sets the color at the center of the path gradient.
//
// Returns:
// A System.Drawing.Color that represents the color at the center of the path gradient.
public Color CenterColor { get; set; }
//
// Summary:
// Gets or sets the focus point for the gradient falloff.
//
// Returns:
// A System.Drawing.PointF that represents the focus point for the gradient falloff.
public PointF FocusScales { get; set; }
//
// Summary:
// Gets or sets a System.Drawing.Drawing2D.WrapMode that indicates the wrap mode
// for this System.Drawing.Drawing2D.PathGradientBrush.
//
// Returns:
// A System.Drawing.Drawing2D.WrapMode that specifies how fills drawn with this
// System.Drawing.Drawing2D.PathGradientBrush are tiled.
public WrapMode WrapMode { get; set; }
//
// Summary:
// Creates an exact copy of this System.Drawing.Drawing2D.PathGradientBrush.
//
// Returns:
// The System.Drawing.Drawing2D.PathGradientBrush this method creates, cast as an
// object.
public override object Clone();
//
// Summary:
// Updates the brush's transformation matrix with the product of brush's transformation
// matrix multiplied by another matrix.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix that will be multiplied by the brush's current
// transformation matrix.
public void MultiplyTransform(Matrix matrix);
//
// Summary:
// Updates the brush's transformation matrix with the product of the brush's transformation
// matrix multiplied by another matrix.
//
// Parameters:
// matrix:
// The System.Drawing.Drawing2D.Matrix that will be multiplied by the brush's current
// transformation matrix.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies in which order to multiply
// the two matrices.
public void MultiplyTransform(Matrix matrix, MatrixOrder order);
//
// Summary:
// Resets the System.Drawing.Drawing2D.PathGradientBrush.Transform property to identity.
public void ResetTransform();
//
// Summary:
// Rotates the local geometric transform by the specified amount. This method prepends
// the rotation to the transform.
//
// Parameters:
// angle:
// The angle (extent) of rotation.
public void RotateTransform(float angle);
//
// Summary:
// Rotates the local geometric transform by the specified amount in the specified
// order.
//
// Parameters:
// angle:
// The angle (extent) of rotation.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies whether to append or prepend
// the rotation matrix.
public void RotateTransform(float angle, MatrixOrder order);
//
// Summary:
// Scales the local geometric transform by the specified amounts. This method prepends
// the scaling matrix to the transform.
//
// Parameters:
// sx:
// The transform scale factor in the x-axis direction.
//
// sy:
// The transform scale factor in the y-axis direction.
public void ScaleTransform(float sx, float sy);
//
// Summary:
// Scales the local geometric transform by the specified amounts in the specified
// order.
//
// Parameters:
// sx:
// The transform scale factor in the x-axis direction.
//
// sy:
// The transform scale factor in the y-axis direction.
//
// order:
// A System.Drawing.Drawing2D.MatrixOrder that specifies whether to append or prepend
// the scaling matrix.
public void ScaleTransform(float sx, float sy, MatrixOrder order);
//
// Summary:
// Creates a gradient with a center color and a linear falloff to each surrounding
// color.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies where, along any radial from the center
// of the path to the path's boundary, the center color will be at its highest intensity.
// A value of 1 (the default) places the highest intensity at the center of the
// path.
//
// scale:
// A value from 0 through 1 that specifies the maximum intensity of the center color
// that gets blended with the boundary color. A value of 1 causes the highest possible
// intensity of the center color, and it is the default value.
public void SetBlendTriangularShape(float focus, float scale);
//
// Summary:
// Creates a gradient with a center color and a linear falloff to one surrounding
// color.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies where, along any radial from the center
// of the path to the path's boundary, the center color will be at its highest intensity.
// A value of 1 (the default) places the highest intensity at the center of the
// path.
public void SetBlendTriangularShape(float focus);
//
// Summary:
// Creates a gradient brush that changes color starting from the center of the path
// outward to the path's boundary. The transition from one color to another is based
// on a bell-shaped curve.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies where, along any radial from the center
// of the path to the path's boundary, the center color will be at its highest intensity.
// A value of 1 (the default) places the highest intensity at the center of the
// path.
//
// scale:
// A value from 0 through 1 that specifies the maximum intensity of the center color
// that gets blended with the boundary color. A value of 1 causes the highest possible
// intensity of the center color, and it is the default value.
public void SetSigmaBellShape(float focus, float scale);
//
// Summary:
// Creates a gradient brush that changes color starting from the center of the path
// outward to the path's boundary. The transition from one color to another is based
// on a bell-shaped curve.
//
// Parameters:
// focus:
// A value from 0 through 1 that specifies where, along any radial from the center
// of the path to the path's boundary, the center color will be at its highest intensity.
// A value of 1 (the default) places the highest intensity at the center of the
// path.
public void SetSigmaBellShape(float focus);
//
// Summary:
// Applies the specified translation to the local geometric transform in the specified
// order.
//
// Parameters:
// dx:
// The value of the translation in x.
//
// dy:
// The value of the translation in y.
//
// order:
// The order (prepend or append) in which to apply the translation.
public void TranslateTransform(float dx, float dy, MatrixOrder order);
//
// Summary:
// Applies the specified translation to the local geometric transform. This method
// prepends the translation to the transform.
//
// Parameters:
// dx:
// The value of the translation in x.
//
// dy:
// The value of the translation in y.
public void TranslateTransform(float dx, float dy);
}
}
从它的构造函数可以看出，其实它就是需要指定一些关键点，有了这些点，它就可以构造一个GraphicsPath，路径可以作为矢量的描述，也就是通常说的放大、缩小不失真。
本例中取了几个随机点，所以，填充看起来，比较抽象……
好了，到这里呢，关于矩形的基本画法就已经全部介绍完了，感觉有点EZ？ BORED？那么我们就来利用现有的知识，再来耍个花活？
6、绘制会浮动的变色魔法箱
1 private Rectangle magicRectangle = Rectangle.Empty;
2 enum Directions : short { UP = 1, RIGHT = 2, DOWN = 4, LEFT = 8, };
3 private Directions direction = Directions.UP | Directions.RIGHT;
4 private Color magicColor = Color.FromArgb(0, 0, 255);
5 private int increament = 1;
6
7 private void btnMagicBox_Click(object sender, EventArgs e)
8 {
9 direction = Directions.UP | Directions.RIGHT;
10
11 magicRectangle = GetRandomRectangle();
12
13 using (var g = CreateGraphics())
14 g.Clear(SystemColors.AppWorkspace);
15
16 timer.Enabled = !timer.Enabled;
17
18 ShowInformation($"魔法箱，开始：{timer.Enabled}。");
19 }
20
21 private void timer_Tick(object sender, EventArgs e)
22 {
23 using (var g = CreateGraphics())
24 using (var brush = new SolidBrush(magicColor))
25 {
26 g.FillRectangle(new SolidBrush(SystemColors.AppWorkspace), magicRectangle);
27
28 magicColor = Color.FromArgb(magicColor.R + increament, magicColor.G + increament, magicColor.B - increament);
29 if (0 == magicColor.R || 255 == magicColor.R) increament = -increament;
30
31 if (magicRectangle.Top <= ClientRectangle.Top && Directions.UP == (direction & Directions.UP))
32 direction = direction ^ Directions.UP | Directions.DOWN;
33
34 if (magicRectangle.Left <= ClientRectangle.Left && Directions.LEFT == (direction & Directions.LEFT))
35 direction = direction ^ Directions.LEFT | Directions.RIGHT;
36
37 if (magicRectangle.Right >= ClientRectangle.Right && Directions.RIGHT == (direction & Directions.RIGHT))
38 direction = direction ^ Directions.RIGHT | Directions.LEFT;
39
40 if (magicRectangle.Bottom >= ClientRectangle.Bottom - pnlToolbox.Height && Directions.DOWN == (direction & Directions.DOWN))
41 direction = direction ^ Directions.DOWN | Directions.UP;
42
43 if (Directions.UP == (direction & Directions.UP)) magicRectangle.Offset(0, -3);
44 if (Directions.LEFT == (direction & Directions.LEFT)) magicRectangle.Offset(-3, 0);
45 if (Directions.RIGHT == (direction & Directions.RIGHT)) magicRectangle.Offset(3, 0);
46 if (Directions.DOWN == (direction & Directions.DOWN)) magicRectangle.Offset(0, 3);
47
48 g.FillRectangle(brush, magicRectangle);
49 }
50
51 }
原理也不复杂，点击“魔法箱”按钮，获取一个随机Rectangle赋值给magicRectangle，切换timer组件的Enable。在timer_Tick事件中，做五件事：
- 将magicRectangle的当前位置填充成背景色；
- 获取一个变化的颜色，为了使颜色不那么跳跃，这里对magicColor的变化作了一些手脚；
- 做碰撞检测，以改变箱子的运动方向；
- 根据箱子的运动方向，用Rectangle.Offset()方法修改矩形的位置；
- 为矩形填充magicColor；
由于截图也看不出动态效果，就不上图了，有兴趣的童鞋可以Run代码看看效果：）
Okay，关于GDI+画矩形的部分，我们就到此告一段落了。
其实说了半天，也没多复杂，基本方法就是Graphics.FillRectangle(Brush brush, Rectangle rect)，区别就在于我们如何构造一个合适的Brush。
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