ASP.NET 生成图片验证码

自己写了一个验证码图片生成的页面

效果如下：

主要实现效果

• 随机渐变背景
• 随机字体颜色（渐变）、大小、角度、扭曲
• 随机干扰曲线

代码如下：

protected void Page_Load(object sender, EventArgs e)
{
    //设置不缓存此页
    Response.AppendHeader("pragma", "no-cache");
    Response.AppendHeader("Cache-Control", "no-cache, must-revalidate");
    Response.AppendHeader("expires", "0");

    Random rand = new Random();

    //获取随机字符
    string str = GetRandString(4);

    //创建画板
    Bitmap image = new Bitmap(80, 26);
    Graphics g = Graphics.FromImage(image);
    //g.InterpolationMode = InterpolationMode.HighQualityBicubic;
    g.InterpolationMode = InterpolationMode.Low;
    //g.CompositingMode = CompositingMode.SourceOver;
    //g.CompositingQuality = CompositingQuality.HighQuality;
    g.CompositingQuality = CompositingQuality.HighSpeed;
    g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
    g.SmoothingMode = SmoothingMode.AntiAlias;

    //绘制渐变背景
    Rectangle rect = new Rectangle(0, 0, image.Width, image.Height);
    Brush brushBack = new LinearGradientBrush(rect, Color.FromArgb(rand.Next(150, 256), 255, 255), Color.FromArgb(255, rand.Next(150, 256), 255), rand.Next(90));
    g.FillRectangle(brushBack, rect);

    //绘制干扰曲线
    for (int i = 0; i < 2; i++)
    {
        Point p1 = new Point(0, rand.Next(image.Height));
        Point p2 = new Point(rand.Next(image.Width), rand.Next(image.Height));
        Point p3 = new Point(rand.Next(image.Width), rand.Next(image.Height));
        Point p4 = new Point(image.Width, rand.Next(image.Height));
        Point[] p = { p1, p2, p3, p4 };
        Pen pen = new Pen(Color.Gray, 1);
        g.DrawBeziers(pen, p);
    }

    //逐个绘制文字
    for (int i = 0; i < str.Length; i++)
    {
        string strChar = str.Substring(i, 1);
        int deg = rand.Next(-15, 15);
        float x = (image.Width / str.Length / 2) + (image.Width / str.Length) * i;
        float y = image.Height / 2;
        //随机字体大小
        Font font = new Font("Consolas", rand.Next(16, 24), FontStyle.Regular);
        SizeF size = g.MeasureString(strChar, font);
        Matrix m = new Matrix();
        //旋转
        m.RotateAt(deg, new PointF(x, y), MatrixOrder.Append);
        //扭曲
        m.Shear(rand.Next(-10, 10) * 0.03f, 0);
        g.Transform = m;
        //随机渐变画笔
        Brush brushPen = new LinearGradientBrush(rect, Color.FromArgb(rand.Next(0, 256), 0, 0), Color.FromArgb(0, 0, rand.Next(0, 256)), rand.Next(90));
        g.DrawString(str.Substring(i, 1), font, brushPen, new PointF(x - size.Width / 2, y - size.Height / 2));

        g.Transform = new Matrix();
    }

    g.Save();
    Response.ContentType = "image/jpeg";
    Response.Clear();
    Response.BufferOutput = true;
    image.Save(Response.OutputStream, ImageFormat.Jpeg);
    g.Dispose();
    image.Dispose();
    Response.Flush();
}

//获取随机数
private string GetRandString(int len)
{
    //string s = "0123456789";
    string s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string str = "";
    Random r = new Random();
    for (int i = 0; i < len; i++)
    {
        str += s.Substring(r.Next(s.Length), 1);
    }
    return str;
}

代码下载：https://files.cnblogs.com/zjfree/RandomImage.rar