用Canvas做的ASP无组件生成图片验证码

源码

    Const cAmount = 36 @# 文字数量
    Const cCode = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
cc=80
kk=30
SafeCode = ""
Session("SafeCode") = ""

BGColor = "FFFFFF"

R = Mid(BGColor,1,2)
G = Mid(BGColor,3,2)
B = Mid(BGColor,5,2)
  


R = DecHex(R)
G = DecHex(G)
B = DecHex(B)

Set objCanvas = New Canvas

objCanvas.GlobalColourTable(0) = RGB(255,255,255) @# White
objCanvas.GlobalColourTable(1) = RGB(0,0,0) @# Black
objCanvas.GlobalColourTable(2) = RGB(255,0,0) @# Red
objCanvas.GlobalColourTable(3) = RGB(0,255,0) @# Green
objCanvas.GlobalColourTable(4) = RGB(0,0,255) @# Blue
objCanvas.GlobalColourTable(5) = RGB(128,0,0)
objCanvas.GlobalColourTable(6) = RGB(0,128,0)
objCanvas.GlobalColourTable(7) = RGB(0,0,128)
objCanvas.GlobalColourTable(8) = RGB(128,128,0)
objCanvas.GlobalColourTable(9) = RGB(0,128,128)
objCanvas.GlobalColourTable(10) = RGB(128,0,128)
objCanvas.GlobalColourTable(11) = RGB(R,G,B)

objCanvas.BackgroundColourIndex = 11

objCanvas.Resize cc,kk,false


@#Randomize timer
@#SafeCode = cint(8999*Rnd+1000)

    Randomize
For i = 0 To 3
  SafeCode = SafeCode &" "& Mid(cCode, Int(Rnd * cAmount) + 1, 1)
    Next
@#杂点
  
For iTemp = 0 To 30
  Randomize timer
  PointX = Int(Rnd * cc)
  PointY = Int(Rnd * kk)
  PointColor = Int(Rnd * 3)+2
  objCanvas.ForegroundColourIndex = PointColor  
  objCanvas.Line PointX,PointY,PointX,PointY
  
  next
@#边框
objCanvas.ForegroundColourIndex = 1
objCanvas.Line 1,1,cc,1
objCanvas.Line 1,kk,1,1
objCanvas.Line 1,kk,cc,kk
objCanvas.Line cc,1,cc,kk

Session("SafeCode") = SafeCode
dim sc,sk
@#文字
Randomize timer
sc = cint(3*Rnd)
sk = cint(3*Rnd)
objCanvas.DrawTextWE sc,sk,SafeCode
objCanvas.Write
  

Function DecHex (HStr)

Dim Result
Dim i,L

Result = 0


L = Len(Hstr)

For i = L-1 To 0 Step -1

  Result = Result + (16 ^ i)*GetDecBit(Mid(HStr,i+1,1))
  
Next

DecHex = Result

End Function

Function GetDecBit (HStr)

Dim Result
Dim R(16)
Dim i

Result = 0

R(0) = "0"
R(1) = "1"
R(2) = "2"
R(3) = "3"
R(4) = "4"
R(5) = "5"
R(6) = "6"
R(7) = "7"
R(8) = "8"
R(9) = "9"
R(10) = "A"
R(11) = "B"
R(12) = "C"
R(13) = "D"
R(14) = "E"
R(15) = "F"

For i = 0 To 15
  
  if HStr=R(i) Then Result = i : Exit For
  
Next

GetDecBit = Result

End Function

原文转自：http://www.ltesting.net