Generation of verification code

When a lot of software logs in , Verification code will be used , As shown in the figure below .

Next, let's share the method of generating verification code . I hope that's helpful

Define a method in the controller

First declare a string , It can be directly assigned to a fixed string , You can also generate a random string

for example ：string strRandom = "abc";

string strRandom = ValidCodeUtils.GetRandomCode(5); Randomly generate one 5 Bit string

notes ：ValidCodeUtils.GetRandomCode Is to create the methods defined in the class , Details of the method are as follows

Create a class and encapsulate the methods you need to use in it for easy use .

Define a method to get a random string

Operations to be implemented ：

Generate random numbers mixed with numbers and passwords

Determines the string based on the current random number

The code is as follows ：

public static string GetRandomCode(int intLength)

        {

            /* Generate random numbers mixed with numbers and passwords */

            string strReturn = string.Empty;

            Random random = new Random();// random number . Represents a pseudo-random number generator

            for (int i = 0; i < intLength; i++)

            {

                char cRerult;

                int intRandom = random.Next();// Generate a nonnegative random integer

                /* Determines the string based on the current random number */

                //intRandom % 3 What you get is intRandom/3 Remainder obtained

                if (intRandom % 3 == 0)

                {

                    // Generate numbers

                    // Number of digits to generate numbers

                    cRerult = (char)(0x30 + (intRandom % 10));

                }

                else if (intRandom % 3 == 1)

                {

                    // The number of digits produces capital letters : Uppercase characters 65-97 A 65

                    //68 D  25 Z

                    cRerult = (char)(0x41 + (intRandom % 0x1a));

                }

                else

                {

                    // Remainder is 2

                    // Produce lowercase letters 98-116

                    cRerult = (char)(0x61 + (intRandom % 0x1a));

                }

                strReturn += cRerult.ToString();

            }

            return strReturn;

        }

Then save the verification code into session conversation

Session["validCode"] = strRandom;

Then generate pictures according to the verification code

byte[] imgByte = ValidCodeUtils.CreateImage(strRandom);

notes ：ValidCodeUtils.CreateImage Is the method defined in the created class , Details are as follows .

Define a method to create a verification code based on a string

Operations to be implemented ：

The new pictures

Draw text on the picture

Draw interference lines on the picture

Draw the foreground interference point of the picture

Draw a border on the outermost side

Save the map to the memory stream

The code is as follows ：

public static byte[] CreateImage(string strRandom)

        {

            // The new pictures

            Bitmap newBitmap = new Bitmap(strRandom.Length * 20, 38);//Bitmap Is used to process image objects defined by pixel data . Initialize with the specified size Bitmap class

            Graphics g = Graphics.FromImage(newBitmap);//Graphics： Encapsulates a GDI+ Drawing picture . From the specified image Create a new Graphics

            g.Clear(Color.White);// Clears the entire drawing surface and fills it with the specified background color

            // Draw text on the picture

            SolidBrush solidBrush = new SolidBrush(Color.Red);//SolidBrush Define a monochrome brush , Used to fill the shape of the drawing

            g.DrawString(strRandom, new Font("Aril", 17), solidBrush, 12, 1);// In the specified position and with the specified Brush and Font Object to draw the specified text string

            // Draw interference lines on the picture

            Random random = new Random();

            for (int i = 0; i < 10; i++)

            {

                // Generate a line , And draw it on the canvas . The starting point （x,y）  Summary point

                int x1 = random.Next(newBitmap.Width);

                int y1 = random.Next(newBitmap.Height);

                int x2 = random.Next(newBitmap.Width);

                int y2 = random.Next(newBitmap.Height);

                g.DrawLine(new Pen(Color.DarkGray), x1, y1, x2, y2);// Draw a line connecting two points specified by a coordinate pair

            }

            // Draw the foreground interference point of the picture

            for (int i = 0; i < 100; i++)

            {

                int x = random.Next(newBitmap.Width);

                int y = random.Next(newBitmap.Height);

                newBitmap.SetPixel(x, y, Color.FromArgb(random.Next()));

            }

            // Draw a border on the outermost side

            g.DrawRectangle(new Pen(Color.Blue), 0, 0, newBitmap.Width, newBitmap.Height);// Draw by coordinate pair 、 Rectangle with specified width and height

            g.DrawRectangle(new Pen(Color.Blue), -1, -1, newBitmap.Width, newBitmap.Height);

            // Save the map to the memory stream

            MemoryStream ms = new MemoryStream();// Create a stream that supports its storage area as memory

            newBitmap.Save(ms, ImageFormat.Jpeg);// Save this picture to the specified stream in the specified format

            return ms.ToArray();// Write the contents of the stream to byte Array return

        }

Finally, return the picture information

return File(imgByte, @"image/jpeg");