


This article will share with you a piece of asp.net code to implement the function of drawing a graphic verification code. The code is simple and easy to understand. The specific code is as follows:
context.Response.ContentType = "image/jpeg"; //生成随机的中文验证码 string yzm = "人口手大小多少上中下男女天地会反清复明杨中科小宝双儿命名空间语现在明天来多个的我山东河北南固安北京南昌东海西安是沙河高教园学" + "木禾上下土个八入大天人火文六七儿九无口日中了子门月不开四五目耳头米见白田电也长山出飞马鸟云公车牛羊小少巾牙尺毛又心手水广升足" + "走方半巴业本平书自已东西回片皮生里果几用鱼今正雨两瓜衣来年左右万百丁齐冬说友话春朋高你绿们花红草爷亲节的岁行古处声知多忙洗真认父扫" + "母爸写全完关家看笑着兴画会妈合奶放午收女气太早去亮和李语秀千香听远唱定连向以更后意主总先起干明赶净同专工才级队蚂蚁前房空网诗黄林闭" + "童立是我朵叶美机她过他时送让吗往吧得虫很河借姐呢呀哪谁凉怕量跟最园脸因阳为光可法石找办许别那到都吓叫再做象点像照沙海桥军竹苗井面乡" + "忘想念王这从进边道贝男原爱虾跑吹乐地老快师短淡对热冷情拉活把种给吃练学习非苦常问伴间共伙汽分要没孩位选北湖南秋江只帮星请雪就球跳玩" + "桃树刚兰座各带坐急名发成动晚新有么在变什条"; Random r = new Random(); string validCode = ""; for (int i = 0; i < 4; i++) { int number = r.Next(0, yzm.Length); validCode += yzm[number]; } //画图 using(Bitmap b = new Bitmap(150, 30)) { using (Graphics g = Graphics.FromImage(b)) using(Font f = new Font("宋体", 20)) { g.Clear(Color.Yellow);//清除整个绘画面并填充指定背景色 g.DrawString(validCode, f, Brushes.Red, new PointF(0, 0));//开始绘制 //前景点 for (int i = 0; i < 100; i++) { int x = r.Next(0, 150); int y = r.Next(0, 30); b.SetPixel(x, y, Color.Red); } //后景线 for (int i = 0; i < 100; i++) { int x = r.Next(0, 150); int y = r.Next(0, 30); g.DrawLine(Pens.Red, x, y, x + 1, y + 1); } } b.Save(context.Response.OutputStream, ImageFormat.Jpeg);//保存到输出流中 }
Reference:
Asp.net development How to implement webform image watermark and image verification code
The above is the implementation code of ASP.NET mid-picture graphic verification code introduced by the editor. I hope it will be helpful to you. If you have any questions Please leave me a message and I will reply to you in time. I would also like to thank you all for your support on the PHP Chinese website!

The char array stores character sequences in C language and is declared as char array_name[size]. The access element is passed through the subscript operator, and the element ends with the null terminator '\0', which represents the end point of the string. The C language provides a variety of string manipulation functions, such as strlen(), strcpy(), strcat() and strcmp().

In C, the char type is used in strings: 1. Store a single character; 2. Use an array to represent a string and end with a null terminator; 3. Operate through a string operation function; 4. Read or output a string from the keyboard.

In C language, special characters are processed through escape sequences, such as: \n represents line breaks. \t means tab character. Use escape sequences or character constants to represent special characters, such as char c = '\n'. Note that the backslash needs to be escaped twice. Different platforms and compilers may have different escape sequences, please consult the documentation.

The usage methods of symbols in C language cover arithmetic, assignment, conditions, logic, bit operators, etc. Arithmetic operators are used for basic mathematical operations, assignment operators are used for assignment and addition, subtraction, multiplication and division assignment, condition operators are used for different operations according to conditions, logical operators are used for logical operations, bit operators are used for bit-level operations, and special constants are used to represent null pointers, end-of-file markers, and non-numeric values.

The difference between multithreading and asynchronous is that multithreading executes multiple threads at the same time, while asynchronously performs operations without blocking the current thread. Multithreading is used for compute-intensive tasks, while asynchronously is used for user interaction. The advantage of multi-threading is to improve computing performance, while the advantage of asynchronous is to not block UI threads. Choosing multithreading or asynchronous depends on the nature of the task: Computation-intensive tasks use multithreading, tasks that interact with external resources and need to keep UI responsiveness use asynchronous.

In C language, char type conversion can be directly converted to another type by: casting: using casting characters. Automatic type conversion: When one type of data can accommodate another type of value, the compiler automatically converts it.

There is no built-in sum function in C language, so it needs to be written by yourself. Sum can be achieved by traversing the array and accumulating elements: Loop version: Sum is calculated using for loop and array length. Pointer version: Use pointers to point to array elements, and efficient summing is achieved through self-increment pointers. Dynamically allocate array version: Dynamically allocate arrays and manage memory yourself, ensuring that allocated memory is freed to prevent memory leaks.

A strategy to avoid errors caused by default in C switch statements: use enums instead of constants, limiting the value of the case statement to a valid member of the enum. Use fallthrough in the last case statement to let the program continue to execute the following code. For switch statements without fallthrough, always add a default statement for error handling or provide default behavior.


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