接着总结ASP.NET,这次主题是图形图像处理,上导图
正如导图所说,GDI+在网页中的应用,经常是验证码和水印,下面总结这两种的代码
验证码:
原理:
- 1.后台cs代码生成随机数,保存到session中(先知道后边会有)
- 2.把随机数写到动态图片中,加上干扰线条
- 3.在提交表单时输入验证码,然后提交过来,然后在后台cs中判断是否和session里的一样
目的:防止机器和病毒暴力破解
下边的代码主要写如何生成一个验证码的类,这个代码网上可以搜的到,仅仅做一个记录
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Web;
namespace Common
{
public class ValidateCode
{
public ValidateCode()
{
}
/// <summary>
/// 验证码的最大长度
/// </summary>
public int MaxLength
{
get { return 10; }
}
/// <summary>
/// 验证码的最小长度
/// </summary>
public int MinLength
{
get { return 1; }
}
/// <summary>
/// 生成验证码
/// </summary>
/// <param name="length">指定验证码的长度</param>
/// <returns></returns>
public string CreateValidateCode(int length)
{
int[] randMembers = new int[length];
int[] validateNums = new int[length];
string validateNumberStr = "";
//生成起始序列值
int seekSeek = unchecked((int)DateTime.Now.Ticks);
Random seekRand = new Random(seekSeek);
int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);
int[] seeks = new int[length];
for (int i = 0; i < length; i++)
{
beginSeek += 10000;
seeks[i] = beginSeek;
}
//生成随机数字
for (int i = 0; i < length; i++)
{
Random rand = new Random(seeks[i]);
int pownum = 1 * (int)Math.Pow(10, length);
randMembers[i] = rand.Next(pownum, Int32.MaxValue);
}
//抽取随机数字
for (int i = 0; i < length; i++)
{
string numStr = randMembers[i].ToString();
int numLength = numStr.Length;
Random rand = new Random();
int numPosition = rand.Next(0, numLength - 1);
validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));
}
//生成验证码
for (int i = 0; i < length; i++)
{
validateNumberStr += validateNums[i].ToString();
}
return validateNumberStr;
}
/// <summary>
/// 创建验证码的图片
/// </summary>
/// <param name="containsPage">要输出到的page对象</param>
/// <param name="validateNum">验证码</param>
public void CreateValidateGraphic(string validateCode, HttpContext context)
{
Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 22);
Graphics g = Graphics.FromImage(image);
try
{
//生成随机生成器
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的干扰线
for (int i = 0; i < 25; 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);
}
Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
//渐变.
LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),
Color.Blue, Color.DarkRed, 1.2f, true);
g.DrawString(validateCode, font, brush, 3, 2);
//画图片的前景干扰点
for (int i = 0; i < 100; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
//保存图片数据
MemoryStream stream = new MemoryStream();
image.Save(stream, ImageFormat.Jpeg);
//输出图片流
context.Response.Clear();
context.Response.ContentType = "image/jpeg";
context.Response.BinaryWrite(stream.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
/// <summary>
/// 得到验证码图片的长度
/// </summary>
/// <param name="validateNumLength">验证码的长度</param>
/// <returns></returns>
public static int GetImageWidth(int validateNumLength)
{
return (int)(validateNumLength * 12.0);
}
/// <summary>
/// 得到验证码的高度
/// </summary>
/// <returns></returns>
public static double GetImageHeight()
{
return 22.5;
}
}
}
想说一下下边的代码
try
{}
catch
{
}
finally
{
g.Dispose();
image.Dispose();
}
因为GDI+中的类生成的对象,很占用资源,所以要及时释放,另外上面的代码就等于using释放资源
为图片添加文字水印
代码如下:
//根据上传成功的图片创建一个image
using (Image img =Image.FromFile(context.Request.MapPath(fullDir)))
{
//根据图片高宽度创建位图
using (Bitmap map = new Bitmap(img.Height,img.Width))
{
//为位图创建画布
using (Graphics g = Graphics.FromImage(map))
{
//用画笔在画布上画图,从画布的左上角开始,将整个图片画到画布上
g.DrawImage(img, 0, 0, img.Height, img.Width);
//为这个图片添加"天地"的水印
g.DrawString("天地", new Font("黑体", 14.0f, FontStyle.Bold), Brushes.Red, new PointF(map.Width-70,map.Height-25));
//为这个图片起一个名字
string waterImageName ="water_"+Guid.NewGuid().ToString();
//保存图片,并指定这个图片的格式
map.Save(context.Request.MapPath("/ImageUpload/"+waterImageName+".jpg"),System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
}
从上边的代码可以看出GDi+图形处理的思路
- 根据上传图片创建image对象
- 根据image对象创建一个位图(bitmap对象)
- 创建一个画布Graphics对象
- 使用Graphics对象的方法进行处理,当然有时候也会有导图中剩下的类
对于第一步有两种方法
1.使用图片路径
Image img =Image.FromFile(context.Request.MapPath(fullDir)
2.使用文件流创建
using(Image img = Image.FromStream(file.InputStream))