在Pen及Brush中都会用到Color结构
常用的是由ARGB组成。A表明透明度，R红色，G绿色，B蓝色。
系统又定义了很多种颜色。
Color属性：
'01.Color的构造与方法 '构造：已知构造与自定义构造 Imports System.Drawing Imports System.Drawing.Text Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click Dim col1 As Color = Color.Red Dim col2 As Color = Color.FromArgb(100,Color.Blue) Dim col3 As Color = Color.FromKnownColor(KnownColor.Chocolate) '从已知颜色中获取（如：系统标题色，窗体背景色等） Dim col4 As Color = Color.FromName("InfoText") '取knownColor中字串颜色，若无此字串，则取色为FromArgb(0,0) Dim br1 As New SolidBrush(col1) Dim br2 As New SolidBrush(col2) Dim br3 As New SolidBrush(col3) Dim br4 As New SolidBrush(col4) Dim s As String Dim gr As Graphics = Me.CreateGraphics gr.FillEllipse(br1,New Rectangle(0,100,100)) gr.FillEllipse(br2,New Rectangle(50,100)) gr.FillEllipse(br3,New Rectangle(25,50,100)) s = "亮度：" & col1.GetBrightness & vbCrLf _ & "哈希码：" & col1.GetHashCode & vbCrLf _ & "色调：" & col1.GetHue & vbCrLf _ & "饱合度：" & col1.GetSaturation & vbCrLf _ & "32位ARGB：" & col1.ToArgb & vbCrLf _ & "实例Type：" & col1.GetType.ToString & vbCrLf _ & "可读字串：" & col1.ToString gr.DrawString(s,Me.Font,br4,New Point(10,150)) End Sub End Class
'02、枚举颜色
'KnownColor是枚举类型，索引0-167，通过FromKnownColor把索引转成对应颜色Color
Imports System.Drawing
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
Dim col(15) As KnownColor
Dim count As Int32 = 0
Dim myColor As Color = Color.FromArgb(255,200,100)
Dim sel As KnownColor
Dim oneColor As Color
Dim gr As Graphics = Me.CreateGraphics
For sel = 0 To KnownColor.YellowGreen '枚举从0索引，每次增1递加(knowncolor共168种，最后yellowgreen为167）
oneColor = Color.FromKnownColor(sel)
If oneColor.GetBrightness < myColor.GetBrightness Then
col(count) = sel
count += 1
If count > 15 Then Exit For
End If
Next
Dim x,y As Int32
x = y = 0
For count = 0 To 15
Dim br As New SolidBrush(Color.FromKnownColor(col(count))) 'knownColor实质上int32
gr.FillRectangle(br,New Rectangle(x,y,20))
If y < 210 Then
y += 30
Else
x = 100
y += 30 - 210
End If
Next
End Sub
End Class
ToArgb方法
此方法返回Color对象的32位Argb值（int32),32位的Argb值的字节顺序是AARRGGBB，
其中：AA是alpha分量值，r,g,b分别对应红、绿、蓝分量
RGB色及多色渐变
可以用FromArgb取得自定义颜色
通过ColorBlend设置好多色及位置数组后，在渐变笔刷中设置Interpolation多色渐变
Imports System.Drawing
Imports System.Drawing.Drawing2D
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
Dim gr As Graphics = Me.CreateGraphics
'渐变方向（由起点到终点）
Dim StartPoint As New Point(20,110)
Dim EndPoint As New Point(140,110)
'多色数组及位置比例数组
Dim myColors As Color() = {Color.FromArgb(0,255,255),Color.FromArgb(0,_
Color.FromArgb(255,0),Color.FromArgb(255,255)}
Dim myPositions As Single() = {0.0F,0.2F,0.4F,0.6F,0.8F,1.0F}'0-1，必须从0开始到1结束
Dim myBlend As New ColorBlend '定义多种颜色及位置比例的对象
myBlend.Colors = myColors
myBlend.Positions = myPositions
Dim lgbr As New LinearGradientBrush(StartPoint,EndPoint,Color.Green,Color.Red)
lgbr.InterpolationColors = myBlend '设置多色渐变
gr.FillEllipse(lgbr,100))
gr.DrawLine(Pens.Black,StartPoint,EndPoint)
End Sub
End Class
复合Alpha （制作透明图）
即生成的位图，在另一处显示时，此位图是透明还是不透明。
若要透明则须复合Alpah混合模式控制。
此时，需要构造空白Bitmap对象，并由它构造Graphics对象。
这时的Graphics对象的CompositingMode属性（枚举）指示：
SourceCopy 指定显示颜色时，将改写背景色（不透明）
SourceOver 指定显示颜色时，将与背景色混合（透明）
'05、复合Alpha，即生成透明图 Imports System.Drawing Imports System.Drawing.Drawing2D Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click Dim gr As Graphics = Me.CreateGraphics Dim bt As New Bitmap(180,100) Dim btgr As Graphics = Graphics.FromImage(bt) Dim redbr As New SolidBrush(Color.FromArgb(210,100)) Dim grebr As New SolidBrush(Color.FromArgb(210,200)) '在位图上画 btgr.CompositingMode = Drawing2D.CompositingMode.SourceOver '关键：设置透明 btgr.FillEllipse(redbr,150,70) btgr.FillEllipse(grebr,30,70) Dim colbr As New SolidBrush(Color.Wheat) gr.CompositingQuality = CompositingQuality.GammaCorrected '复合质量控制：灰度校正 '画三个矩形组成一个大的矩形图，用于后面再成图时显示透明效果 gr.FillRectangle(colbr,60,100) colbr.Color = Color.Black gr.FillRectangle(colbr,260,100) colbr.Color = Color.Tan gr.FillRectangle(colbr,320,100) '把位图画上 gr.DrawImage(bt,0) '背景为窗体时 gr.DrawImage(bt,0) '背景为矩形（三个矩形组成） PictureBox1.Image = bt bt.Save("D:\1.jpg") End Sub End Class
06、颜色矩阵设置图像Alpha值（透明）
Bitmap类（继承自Image类）和ImageAttribute类可设置和获取Alpha值。
1、用ImageAttributes类修改图形的Alpha值
2、用Bitmap类SetPixel设置单个像素值
由于上面修改了Alpha值，所以也可以有透明效果。
'06、矩阵调整设置Alpha值，呈现透明效果 Imports System.Drawing Imports System.Drawing.Imaging Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click Dim gr As Graphics = Me.CreateGraphics Dim bm As New Bitmap("D:\1.jpg") '颜色调整矩阵5X5，分别为A,R,G,B,W，其中W固定为1 Dim MatrixItems As Single()() = {New Single() {1,0},New Single() {0,1,_ New Single() {0,1}} Dim colMatr As New Imaging.ColorMatrix(MatrixItems) Dim imageAtt As New ImageAttributes imageAtt.SetColorMatrix(colMatr,ColorMatrixFlag.Default,ColorAdjustType.Bitmap) gr.DrawLine(New Pen(Color.Black,25),New Point(160,35),New Point(270,35)) gr.DrawImage(bm,bm.Width,bm.Height),0.0F,bm.Height,GraphicsUnit.Pixel,imageAtt) End Sub End Class
07、线性渐变的Gamma校正
前面多次用线性渐变举例，下面将使用线性渐变笔刷的Gamma校正。
Gamma校正，会使颜色的亮度更均匀。默认下，Gamma校正是禁止的。
'07、线性渐变
Imports System.Drawing
Imports System.Drawing.Drawing2D
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
Dim gr As Graphics = Me.CreateGraphics
Dim lgbr As New LinearGradientBrush(New Point(0,New Point(300,Color.Black,Color.Wheat)
gr.FillRectangle(lgbr,10,50))
lgbr.GammaCorrection = True '启用灰度校正，颜色的亮度更均匀
gr.FillRectangle(lgbr,70,50))
End Sub
End Class