Implement verification code with interference lines through Java

1. Project Overview

Verification codes with interference lines are a common security verification method. The purpose is to increase the difficulty of machine recognition through interference lines in the image, ensuring that only human users can successfully identify and enter verification codes. Verification codes usually include random characters and will make it impossible to easily crack the automated recognition systems (such as OCRs) through technical means such as interference lines, noises or background patterns.

The purpose of this project is to implement a verification code generator with interference lines through Java. The generated verification code not only contains random characters, but also randomly draws interference lines to increase the security of the verification code. It can be applied to user registration, login, payment and other scenarios to prevent malicious robots from performing automated operations.

2. Related knowledge

When implementing verification codes with interference lines, you need to understand the following key technical points:

• Java Image Processing: JavaBufferedImageClasses provide the creation and processing of images, and can draw various elements on the images.
• Drawing of interference lines: Using Java's graphics drawing function, random interference lines can be drawn on the verification code image, increasing the difficulty of recognition.
• Font and color: By setting random fonts and colors, the appearance of verification code characters is more complicated.
• Random number generation: Generate random verification code strings and interference lines coordinates, colors, etc. to ensure that the verification code generated each time is unique.

3. Project implementation ideas

We will implement the generation of verification codes in step by step, including the following steps:

1. Generate random verification code string: Generate a verification code string composed of letters and numbers.
2. Create image canvas:useBufferedImageCreate a blank image as the canvas.
3. Draw verification code characters: Randomly select the font, color and position, and draw the verification code characters.
4. Add a disturbance line: Randomly generates the start and end coordinates of the interference line and draws the interference line.
5. Output verification code image: The generated verification code image is output to an image format (such as JPEG or PNG), which can be returned through an HTTP response.

4. Project code implementation

import ;
import .*;
import ;
import ;
import ;
import ;
 
public class CaptchaGenerator {
 
    // Set the width and height of the verification code    private static final int WIDTH = 160;
    private static final int HEIGHT = 50;
 
    // Verification code character set, can be extended as needed    private static final String CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
 
    // Random number generator    private static final Random random = new Random();
 
    // Method for generating verification code    public static void generateCaptcha(OutputStream out) throws IOException {
        // Create a blank image canvas        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = ();
 
        // Set the background color of the image to white        ();
        (0, 0, WIDTH, HEIGHT);
 
        // Draw the interference line        drawNoiseLines(graphics);
 
        // Draw verification code characters        String captchaText = generateRandomText();
        drawCaptchaText(graphics, captchaText);
 
        // Output verification code image        (image, "JPEG", out);
        ();
    }
 
    // Generate a random verification code string    private static String generateRandomText() {
        StringBuilder captchaText = new StringBuilder();
        for (int i = 0; i < 6; i++) {
            int index = (());
            ((index));
        }
        return ();
    }
 
    // Draw verification code characters on the image    private static void drawCaptchaText(Graphics2D graphics, String captchaText) {
        // Set random fonts and colors        (new Font("Arial", , 40));
        for (int i = 0; i < (); i++) {
            char c = (i);
            (getRandomColor());
            // Set the character position            ((c), 20 + i * 25, 40);
        }
    }
 
    // Draw the interference line    private static void drawNoiseLines(Graphics2D graphics) {
        for (int i = 0; i < 10; i++) {
            // Randomly generate coordinates of interference lines            int x1 = (WIDTH);
            int y1 = (HEIGHT);
            int x2 = (WIDTH);
            int y2 = (HEIGHT);
 
            // Set the color of the interference line            (getRandomColor());
            // Draw the interference line            (x1, y1, x2, y2);
        }
    }
 
    // Get a random color    private static Color getRandomColor() {
        int r = (256);
        int g = (256);
        int b = (256);
        return new Color(r, g, b);
    }
 
    // Main method, used for testing    public static void main(String[] args) {
        try {
            // Analog output verification code image            OutputStream out = ;  // Use analog output stream here            generateCaptcha(out);
        } catch (IOException e) {
            ();
        }
    }
}

5. Code interpretation

1. generateCaptchamethod: This method is the core of verification code generation, which is responsible for creating images, drawing interference lines, drawing verification code characters, and outputting the image to the specified output stream.

   • useBufferedImageCreates a new image object that specifies the width, length, and type of the image.
   • useGraphics2DThe object is drawn.
   • Set image background to white.
   • CalldrawNoiseLinesThe method generates interference lines, increasing the complexity of the verification code.
   • CalldrawCaptchaTextMethod draws the verification code string.

2. generateRandomTextmethod: This method generates a 6-bit random verification code string, the characters can be upper and lower case letters and numbers.

3. drawCaptchaTextmethod: This method is responsible for drawing the generated verification code characters onto the image. Each character has a random color and position.

4. drawNoiseLinesmethod: This method draws 10 random disturbance lines. The start and end coordinates of each disturbance line are randomly generated and the colors are also randomly selected. The interference line can effectively prevent the machine from automatically identifying the verification code.

5. getRandomColormethod: This method generates a random RGB color for drawing verification code characters and interference lines.

6. mainmethod: This is a simple test method for simulation output verification code images. In actual projects, the generated verification code can be returned to the user through an HTTP response.

6. Project Summary

Through this project, we implement a verification code generation system with interference lines. Through the randomly generated characters, interference lines and colors, the verification code not only has good randomness, but also increases the difficulty of preventing machine recognition, and improves the security of the system. This verification code can be widely used in user login, registration, payment and other scenarios, effectively preventing malicious robots from submitting forms.

During the implementation process, we used Java's graphics drawing function and mastered how to use itGraphics2DClass draws image elements and passesRandomThe class generates verification code characters and interference elements. This project has high scalability and can meet the needs of different scenarios by adjusting the length of verification code characters, fonts, number of interference lines, etc.

7. Extension and optimization

1. Add image distortion: The verification code characters can be deformed through image distortion technology, making them more difficult to recognize.
2. More distraction elements: In addition to interference lines, you can consider adding elements such as noise and background patterns to further increase the complexity of the verification code.
3. Supports multilingual: Different character sets can be provided for users of different languages.
4. User experience optimization: Allows users to refresh and obtain new verification code when they cannot recognize the verification code.

Through continuous optimization and adjustment, we can design a safer and easier to use verification code system.

This is the end of this article about implementing verification codes with interference lines through Java. For more related Java interference line verification code content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!

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