开发基于ASP.NET WebService的图片验证码服务

System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(nBmpWidth,nBmpHeight);

// 1. 生成随机背景颜色

int nRed,nGreen,nBlue; // 背景的三元色

System.Random rd = new Random((int)System.DateTime.Now.Ticks);

nRed = rd.Next(255)%128+128;

nGreen = rd.Next(255)%128+128;

nBlue = rd.Next(255)%128+128;

// 2. 填充位图背景

System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(bmp);

graph.FillRectangle(new SolidBrush(System.Drawing.Color.FromArgb(nRed,nGreen,nBlue))

,0

,0

,nBmpWidth

,nBmpHeight);

// 3. 绘制干扰线条，采用比背景略深一些的颜色

int nLines = 3;

System.Drawing.Pen pen = new System.Drawing.Pen(System.Drawing.Color.FromArgb(nRed-17,nGreen-17,nBlue-17),2);

for(int a =0;a< nLines;a++)

{

int x1 = rd.Next() % nBmpWidth;

int y1 = rd.Next() % nBmpHeight;

int x2 = rd.Next() % nBmpWidth;