小巧方便的MVC後端驗證碼，供大家學習借鑒

調用：

public ActionResult Vcode()//驗證碼
{

　　string code = ValidateCode.CreateRandomCode(4);

　　ValidateCode.CreateImage(code);

　　Session["vcode"] = code.ToLower();//存入session供驗證用

　　System.IO.MemoryStream ms = new System.IO.MemoryStream();

　　return File(ms.GetBuffer(), "image/JPEG");

}

//下麵是主題class內部

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Web;

namespace xxxxxx.Models//命名空間自己填咯
{
public class ValidateCode
{
public static string CreateRandomCode(int length)
{
int rand;
char code;
string randomcode = String.Empty;
//生成一定長度的驗證碼
System.Random random = new Random();
for (int i = 0; i < length; i++)
{
rand = random.Next();
if (rand % 3 == 0)
{
code = (char)('A' + (char)(rand % 26));//如果是3的倍數就除以26將餘數（小於26）轉換成大寫字母
}
else if (rand % 7 == 0)
{
code = (char)('a' + (char)(rand % 26));
}
else
{
code = (char)('0' + (char)(rand % 10));
}
randomcode += code.ToString();
}

return randomcode;
}
public static void CreateImage(string randomcode)
{
int randAngle = 30; //隨機轉動角度範圍
int mapwidth = (int)(randomcode.Length * 23);//背景的寬度，此值是你輸入要求的字元長度的23倍大(4*23=92寬)
using (Bitmap map = new Bitmap(mapwidth, 28))//創建圖片背景，寬為（4*28），高為28的畫布，從右上角（0，0）處開始;
{
Random rand = new Random();//隨機數實例
using (Bitmap temp = new Bitmap(map.Width, map.Height))//臨時畫布
{
using (Graphics tempGra = Graphics.FromImage(temp))
{
char[] chars = randomcode.ToCharArray();//拆散字元串成單字元數組
StringFormat format = new StringFormat(StringFormatFlags.NoClip);//定義文字格式
format.Alignment = StringAlignment.Center;//文字距中
format.LineAlignment = StringAlignment.Center;
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //定義顏色
string[] fontList = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋體" };//定義字體
for (int i = 0; i < chars.Length; i++)//逐個繪製文字
{
int cindex = rand.Next(7);//顏色隨機數
int findex = rand.Next(5);//字體隨機數
Font font = new System.Drawing.Font(fontList[findex], 13, System.Drawing.FontStyle.Bold);//字體樣式(參數2為字體大小)
Brush brush = new System.Drawing.SolidBrush(c[cindex]);//文字顏色1
//Brush brushPen = new LinearGradientBrush(new Rectangle(0, 0, temp.Width, temp.Height), Color.FromArgb(rand.Next(0, 256), 0, 0), Color.FromArgb(0, 0, rand.Next(0, 256)), rand.Next(90));//文字顏色2漸變
Point dot = new Point(16, 14);//定義一個點
//graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);//測試X坐標顯示間距的
float angle = rand.Next(-randAngle, randAngle);//轉動的度數
tempGra.TranslateTransform(dot.X, dot.Y);//更改坐標系的原點(所有的操作在此原點(16,16))
tempGra.RotateTransform(angle);//旋轉畫布
//Matrix m = new Matrix();//創建變換
//m.RotateAt(angle, new PointF(16, 16), MatrixOrder.Append);//旋轉
//m.Shear(rand.Next(-10, 10) * 0.03f, 0);//扭曲
//tempGra.Transform = m;//畫布應用變換
tempGra.DrawString(chars[i].ToString(), font, brush, 1, 1, format);//開始畫字母或文字
tempGra.RotateTransform(-angle);//轉回去
tempGra.TranslateTransform(4, -dot.Y);//更改坐標系的原點
}
}
using (Graphics graph = Graphics.FromImage(map))//創建目標畫布;
{
graph.Clear(Color.AliceBlue);//清除畫面，填充背景
Rectangle rect = new Rectangle(0, 0, map.Width, map.Height);//繪製漸變背景
Brush brushBack = new LinearGradientBrush(rect, Color.FromArgb(rand.Next(150, 256), 255, 255), Color.FromArgb(255, rand.Next(150, 256), 255), rand.Next(90));//漸變背景顏色
graph.FillRectangle(brushBack, rect);//背景填充到畫布
graph.DrawRectangle(new Pen(Color.LightPink, 0), 0, 0, map.Width - 1, map.Height - 1);//畫一個邊框,預設是從屏幕右上角（0，0）初開始畫
//graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//圖片抗鋸齒模式

Pen blackPen = new Pen(Color.LightGray, 0);//筆觸顏色
for (int i = 0; i < 50; i++)//噪點50個
{
int x = rand.Next(1, map.Width - 3);
int y = rand.Next(1, map.Height - 3);
graph.DrawRectangle(blackPen, x, y, 1, 1);//生成噪點
}
graph.DrawImage(temp, new Point(0, 0));//先畫點後畫圖
Pen pen = new Pen(Color.Gray, 1);//干擾線筆觸
for (int i = 0; i < 2; i++)//繪製兩條幹擾線
{
Point p1 = new Point(0, rand.Next(map.Height));
Point p2 = new Point(rand.Next(map.Width), rand.Next(map.Height));
Point p3 = new Point(rand.Next(map.Width), rand.Next(map.Height));
Point p4 = new Point(map.Width, rand.Next(map.Height));
Point[] p = { p1, p2, p3, p4 };
graph.DrawBeziers(pen, p);
}
System.IO.MemoryStream ms = new System.IO.MemoryStream();
map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ContentType = "image/gif";
HttpContext.Current.Response.BinaryWrite(ms.ToArray());
temp.Dispose();//釋放
graph.Dispose();
map.Dispose();
}
}
}

}
}
}