http://blog.csdn.net/laviewpbt/article/details/1568060
Private Declare Function GetPixel Lib "gdi32" (ByVal hDC As Long, ByVal X As Long, ByVal Y As Long) As Long
Private Declare Function SetPixel Lib "gdi32" (ByVal hDC As Long, ByVal X As Long, ByVal Y As Long, ByVal crColor As Long) As Long
'
Private Const PI = 3.1415926 / 180
Private Sub PsetEx(Pic As PictureBox, X As Single, Y As Single, Optional Color As Long = 0)
Dim CenterX As Long, CenterY As Long, CenterColor As Long, CenterAlpha As Single
Dim CenterRX As Long, CenterRY As Long, CenterRColor As Long, CenterRAlpha As Single
Dim CenterBX As Long, CenterBy As Long, CenterBColor As Long, CenterBAlpha As Single
Dim CenterRBX As Long, CenterRBY As Long, CenterRBColor As Long, CenterRBAlpha As Single
Dim hDC As Long
hDC = Pic.hDC
CenterX = Int(X)
CenterY = Int(Y)
CenterColor = GetPixel(hDC, CenterX, CenterY)
CenterAlpha = (CenterX - X + 1) * (CenterY - Y + 1)
CenterRX = CenterX + 1
CenterRY = Int(Y)
CenterRColor = GetPixel(hDC, CenterRX, CenterRY)
CenterRAlpha = (X - CenterRX + 1) * (CenterY - Y + 1)
CenterBX = CenterX
CenterBy = CenterY + 1
CenterBColor = GetPixel(hDC, CenterBX, CenterBy)
CenterBAlpha = (CenterX - X + 1) * (Y - CenterBy + 1)
CenterRBX = CenterX + 1
CenterRBY = CenterY + 1
CenterRBColor = GetPixel(hDC, CenterRBX, CenterRBY)
CenterRBAlpha = (X - CenterRX + 1) * (Y - CenterBy + 1)
SetPixel hDC, CenterX, CenterY, BlendColor(CenterColor, Color, CenterAlpha)
SetPixel hDC, CenterRX, CenterRY, BlendColor(CenterRColor, Color, CenterRAlpha)
SetPixel hDC, CenterBX, CenterBy, BlendColor(CenterBColor, Color, CenterBAlpha)
SetPixel hDC, CenterRBX, CenterRBY, BlendColor(CenterRBColor, Color, CenterRBAlpha)
End Sub
'
Private Sub GetRGB(Color As Long, Red As Long, Green As Long, Blue As Long)
If Color <> 0 Then
Red = Color And 255&
Green = Color / 256 And 255
Blue = Color / 65536
End If
End Sub
Private Function BlendColor(ColorBase As Long, ColorBlend As Long, Alpha As Single) As Long
Dim BaseR As Long, BaseG As Long, BaseB As Long
Dim BlendR As Long, BlendG As Long, BlendB As Long
GetRGB ColorBase, BaseR, BaseG, BaseB
GetRGB ColorBlend, BlendR, BlendG, BlendB
If Alpha > 1 Then Alpha = 1
BaseR = Alpha * (BlendR - BaseR) + BaseR
BaseG = Alpha * (BlendG - BaseG) + BaseG
BaseB = Alpha * (BlendB - BaseB) + BaseB
BlendColor = RGB(BaseR, BaseG, BaseB)
End Function
'
Private Sub CircleEx(Pic As PictureBox, CenterX As Long, CenterY As Long, Radius As Long, Optional Color As Long = vbRed)
Dim i As Single
Dim X As Single, Y As Single
For i = 0 To 360 Step 60 / Radius
X = Cos(i * PI)
Y = Sin(i * PI)
X = X * Radius + CenterX
Y = Y * Radius + CenterY
PsetEx Pic, X, Y, Color
Next
End Sub
Private Sub Command1_Click()
CircleEx Pic, 100, 100, 50, vbRed
Pic.Refresh
End Sub
以这种方式画抗锯齿的直线时要注意对于斜率大于和小于1的情况要分开处理，这里不赘述！
如果你觉得画出来的圆颜色和指定的颜色有所区别，请适当修改PsetEx函数的最后四行的SetPixel的最后一个透明度的参数，比如都乘2！.