本文实例讲述了c#实现的一款比较美观的验证码。分享给大家供大家参考，具体如下：
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using system;
using system.collections.generic;
using system.web;
using system.web.ui;
using system.web.ui.webcontrols;
using system.drawing;
using system.io;
using system.drawing.imaging;
public partial class validatecode : system.web.ui.page
{
private int letterwidth = 16;//单个字体的宽度范围
private int letterheight = 22;//单个字体的高度范围
private int lettercount = 4;//验证码位数
private char[] chars = "0123456789".tochararray();
private string[] fonts = { "arial", "georgia" };
/// <summary>
/// 产生波形滤镜效果
/// </summary>
private const double pi = 3.1415926535897932384626433832795;
private const double pi2 = 6.283185307179586476925286766559;
protected void page_load(object sender, eventargs e)
{
//防止网页后退--禁止缓存
response.expires = 0;
response.buffer = true;
response.expiresabsolute = datetime.now.addseconds(-1);
response.addheader("pragma", "no-cache");
response.cachecontrol = "no-cache";
string str_validatecode = getrandomnumberstring(lettercount);
httpcookie objcookie = new httpcookie("validatecode");
objcookie.value = str_validatecode;
objcookie.path = "/";
objcookie.expires = datetime.now.addseconds(1200);
response.cookies.add(objcookie);
createimage(str_validatecode);
}
public void createimage(string checkcode)
{
int int_imagewidth = checkcode.length * letterwidth;
random newrandom = new random();
bitmap image = new bitmap(int_imagewidth, letterheight);
graphics g = graphics.fromimage(image);
//生成随机生成器
random random = new random();
//白色背景
g.clear(color.white);
//画图片的背景噪音线
for (int i = 0; i < 10; i++)
{
int x1 = random.next(image.width);
int x2 = random.next(image.width);
int y1 = random.next(image.height);
int y2 = random.next(image.height);
g.drawline(new pen(color.silver), x1, y1, x2, y2);
}
//画图片的前景噪音点
for (int i = 0; i < 10; i++)
{
int x = random.next(image.width);
int y = random.next(image.height);
image.setpixel(x, y, color.fromargb(random.next()));
}
//随机字体和颜色的验证码字符
int findex;
for (int int_index = 0; int_index < checkcode.length; int_index++)
{
findex = newrandom.next(fonts.length - 1);
string str_char = checkcode.substring(int_index, 1);
brush newbrush = new solidbrush(getrandomcolor());
point thepos = new point(int_index * letterwidth + 1 + newrandom.next(3), 1 + newrandom.next(3));//5+1+a+s+p+x
g.drawstring(str_char, new font(fonts[findex], 12, fontstyle.bold), newbrush, thepos);
}
//灰色边框
g.drawrectangle(new pen(color.lightgray, 1), 0, 0, int_imagewidth - 1, (letterheight - 1));
//图片扭曲
//image = twistimage(image, true, 3, 4);
//将生成的图片发回客户端
memorystream ms = new memorystream();
image.save(ms, imageformat.png);
response.clearcontent(); //需要输出图象信息 要修改http头
response.contenttype = "image/png";
response.binarywrite(ms.toarray());
g.dispose();
image.dispose();
}
/// <summary>
/// 正弦曲线wave扭曲图片
/// </summary>
/// <param name="srcbmp">图片路径</param>
/// <param name="bxdir">如果扭曲则选择为true</param>
/// <param name="nmultvalue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>
/// <param name="dphase">波形的起始相位，取值区间[0-2*pi)</param>
/// <returns></returns>
public system.drawing.bitmap twistimage(bitmap srcbmp, bool bxdir, double dmultvalue, double dphase)
{
system.drawing.bitmap destbmp = new bitmap(srcbmp.width, srcbmp.height);
// 将位图背景填充为白色
system.drawing.graphics graph = system.drawing.graphics.fromimage(destbmp);
graph.fillrectangle(new solidbrush(system.drawing.color.white), 0, 0, destbmp.width, destbmp.height);
graph.dispose();
double dbaseaxislen = bxdir ? (double)destbmp.height : (double)destbmp.width;
for (int i = 0; i < destbmp.width; i++)
{
for (int j = 0; j < destbmp.height; j++)
{
double dx = 0;
dx = bxdir ? (pi2 * (double)j) / dbaseaxislen : (pi2 * (double)i) / dbaseaxislen;
dx += dphase;
double dy = math.sin(dx);
// 取得当前点的颜色
int noldx = 0, noldy = 0;
noldx = bxdir ? i + (int)(dy * dmultvalue) : i;
noldy = bxdir ? j : j + (int)(dy * dmultvalue);
system.drawing.color color = srcbmp.getpixel(i, j);
if (noldx >= 0 && noldx < destbmp.width && noldy >= 0 && noldy < destbmp.height)
{
destbmp.setpixel(noldx, noldy, color);
}
}
}
return destbmp;
}
public color getrandomcolor()
{
random randomnum_first = new random((int)datetime.now.ticks);
system.threading.thread.sleep(randomnum_first.next(50));
random randomnum_sencond = new random((int)datetime.now.ticks);
int int_red = randomnum_first.next(210);
int int_green = randomnum_sencond.next(180);
int int_blue = (int_red + int_green > 300) ? 0 : 400 - int_red - int_green;
int_blue = (int_blue > 255) ? 255 : int_blue;
return color.fromargb(int_red, int_green, int_blue);// 5+1+a+s+p+x
}
// 生成随机数字字符串
public string getrandomnumberstring(int int_numberlength)
{
random random = new random();
string validatecode = string.empty;
for (int i = 0; i < int_numberlength; i++)
validatecode += chars[random.next(0, chars.length)].tostring();
return validatecode;
}
}
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