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<%
option explicit " 显示声明

class com_gifcode_class
"""""""""""""""""""""""""""""""""""""""""""""
" author: layen support@ssaw.net 84815733(qq)
" thanks: laomi, laomiao, netrube
" 2006-01-02
"""""""""""""""""""""""""""""""""""""""""""""
public noisy, count, width, height, angle, offset, border

private graph(), margin(3)

private sub class_initialize()
randomize
noisy = 1 " 干扰点出现的概率
count = 4 " 字符数量
width = 80 " 图片宽度
height = 20 " 图片高度
angle = 1 " 角度随机变化量
offset = 10 " 偏移随机变化量
border = 1 " 边框大小
end sub

public function create()

const ccharset = "123456789"

dim i, x, y

dim vvalidcode : vvalidcode = ""
dim vindex

redim graph(width-1, height-1)

for i = 0 to count - 1
vindex = int(rnd * len(ccharset))
vvalidcode = vvalidcode + mid(ccharset, vindex+1 , 1)
setdraw vindex, i
next

create = vvalidcode

end function

sub setdot(px, py)
if px * (width-px-1) >= 0 and py * (height-py-1) >= 0 then
graph(px, py) = 1
end if
end sub

public sub setdraw(pindex, pnumber)

" 字符数据
dim dotdata(8)
dotdata(0) = array(30, 15, 50, 1, 50, 100)
dotdata(1) = array(1 ,34 ,30 ,1 ,71, 1, 100, 34, 1, 100, 93, 100, 100, 86)
dotdata(2) = array(1, 1, 100, 1, 42, 42, 100, 70, 50, 100, 1, 70)
dotdata(3) = array(100, 73, 6, 73, 75, 6, 75, 100)
dotdata(4) = array(100, 1, 1, 1, 1, 50, 50, 35, 100, 55, 100, 80, 50, 100, 1, 95)
dotdata(5) = array(100, 20, 70, 1, 20, 1, 1, 30, 1, 80, 30, 100, 70, 100, 100, 80, 100, 60, 70, 50, 30, 50, 1, 60)
dotdata(6) = array(6, 26, 6, 6, 100, 6, 53, 100)
dotdata(7) = array(100, 30, 100, 20, 70, 1, 30, 1, 1, 20, 1, 30, 100, 70, 100, 80, 70, 100, 30, 100, 1, 80, 1, 70, 100, 30)
dotdata(8) = array(1, 80, 30, 100, 80, 100, 100, 70, 100, 20, 70, 1, 30, 1, 1, 20, 1, 40, 30, 50, 70, 50, 100, 40)

dim vextent : vextent = width / count
margin(0) = border + vextent * (rnd * offset) / 100 + margin(1)
margin(1) = vextent * (pnumber + 1) - border - vextent * (rnd * offset) / 100
margin(2) = border + height * (rnd * offset) / 100
margin(3) = height - border - height * (rnd * offset) / 100

dim vstartx, vendx, vstarty, vendy
dim vwidth, vheight, vdx, vdy, vdeltat

dim vangle, vlength

vwidth = int(margin(1) - margin(0))

vheight = int(margin(3) - margin(2))

" 起始坐标
vstartx = int((dotdata(pindex)(0)-1) * vwidth / 100)

vstarty = int((dotdata(pindex)(1)-1) * vheight / 100)

dim i, j
for i = 1 to ubound(dotdata(pindex), 1)/2

if dotdata(pindex)(2*i-2) <> 0 and dotdata(pindex)(2*i) <> 0 then

" 终点坐标
vendx = (dotdata(pindex)(2*i)-1) * vwidth / 100

vendy = (dotdata(pindex)(2*i+1)-1) * vheight / 100

" 横向差距
vdx = vendx - vstartx
" 纵向差距
vdy = vendy - vstarty

" 倾斜角度
if vdx = 0 then
vangle = sgn(vdy) * 3.14/2
else
vangle = atn(vdy / vdx)
end if

" 两坐标距离
if sin(vangle) = 0 then
vlength = vdx
else
vlength = vdy / sin(vangle)
end if

" 随机转动角度
vangle = vangle + (rnd - 0.5) * 2 * angle * 3.14 * 2 / 100

vdx = int(cos(vangle) * vlength)

vdy = int(sin(vangle) * vlength)

if abs(vdx) > abs(vdy) then vdeltat = abs(vdx) else vdeltat = abs(vdy)

for j = 1 to vdeltat
setdot margin(0) + vstartx + j * vdx / vdeltat, margin(2) + vstarty + j * vdy / vdeltat
next

vstartx = vstartx + vdx

vstarty = vstarty + vdy
end if
next
end sub

public sub output()

response.expires = -9999
response.addheader "pragma", "no-cache"
response.addheader "cache-ctrol", "no-cache"
response.contenttype = "image/gif"

" 文件类型
response.binarywrite chrb(asc("g")) & chrb(asc("i")) & chrb(asc("f"))
" 版本信息
response.binarywrite chrb(asc("8")) & chrb(asc("9")) & chrb(asc("a"))
" 逻辑屏幕宽度
response.binarywrite chrb(width mod 256) & chrb((width 256) mod 256)
" 逻辑屏幕高度
response.binarywrite chrb(height mod 256) & chrb((height 256) mod 256)

response.binarywrite chrb(128) & chrb(0) & chrb(0)
" 全局颜色列表
response.binarywrite chrb(255) & chrb(255) & chrb(255)

response.binarywrite chrb(0) & chrb(0) & chrb(0)

" 图象标识符
response.binarywrite chrb(asc(","))

response.binarywrite chrb(0) & chrb(0) & chrb(0) & chrb(0)
" 图象宽度
response.binarywrite chrb(width mod 256) & chrb((width 256) mod 256)
" 图象高度
response.binarywrite chrb(height mod 256) & chrb((height 256) mod 256)

response.binarywrite chrb(0) & chrb(7) & chrb(255)

dim x, y, i : i = 0
for y = 0 to height - 1
for x = 0 to width - 1
if rnd < noisy / 100 then
response.binarywrite chrb(1-graph(x, y))
else
if x * (x-width) = 0 or y * (y-height) = 0 then
response.binarywrite chrb(graph(x, y))
else
if graph(x-1, y) = 1 or graph(x, y) or graph(x, y-1) = 1 then
response.binarywrite chrb(1)
else
response.binarywrite chrb(0)
end if
end if
end if
if (y * width + x + 1) mod 126 = 0 then
response.binarywrite chrb(128)
i = i + 1
end if
if (y * width + x + i + 1) mod 255 = 0 then
if (width*height - y * width - x - 1) > 255 then
response.binarywrite chrb(255)
else
response.binarywrite chrb(width * height mod 255)
end if
end if
next
next
response.binarywrite chrb(128) & chrb(0) & chrb(129) & chrb(0) & chrb(59)
end sub
end class

dim mcode
set mcode = new com_gifcode_class
session("getcode") = mcode.create()
mcode.output()
set mcode = nothing
%>

本文来源：http://www.gdgbn.com/zhufuduanxin/28181/