lc-core/src/main/java/lc/ShadowTextCaptcha.java

package lc;

import javax.imageio.ImageIO;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.Font;
import java.awt.font.TextLayout;
import java.awt.image.BufferedImage;
import java.awt.image.ConvolveOp;
import java.awt.image.Kernel;
import java.io.ByteArrayOutputStream;

public class ShadowTextCaptcha implements ChallengeProvider{

    public String getId() {
        return "ShadowText";
    }

    public boolean checkAnswer(String secret, String answer) {
        return answer.toLowerCase().equals(secret);
    }

    private byte[] shadowText(String text){
        BufferedImage img = new BufferedImage(350, 100, BufferedImage.TYPE_INT_RGB);
        Font font = new Font("Arial",Font.ROMAN_BASELINE ,48);
        Graphics2D graphics2D = img.createGraphics();
        TextLayout textLayout = new TextLayout(text, font, graphics2D.getFontRenderContext());
        HelperFunctions.setRenderingHints(graphics2D);
        graphics2D.setPaint(Color.WHITE);
        graphics2D.fillRect(0, 0, 350, 100);
        graphics2D.setPaint(Color.BLACK);
        textLayout.draw(graphics2D, 15, 50);
        graphics2D.dispose();
        float[] kernel = {
                1f / 9f, 1f / 9f, 1f / 9f,
                1f / 9f, 1f / 9f, 1f / 9f,
                1f / 9f, 1f / 9f, 1f / 9f
        };
        ConvolveOp op =  new ConvolveOp(new Kernel(3, 3, kernel),
                ConvolveOp.EDGE_NO_OP, null);
        BufferedImage img2 = op.filter(img, null);
        Graphics2D g2d = img2.createGraphics();
        HelperFunctions.setRenderingHints(g2d);
        g2d.setPaint(Color.WHITE);
        textLayout.draw(g2d, 13, 50);
        g2d.dispose();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            ImageIO.write(img2,"png",baos);
        }catch(Exception e){
            e.printStackTrace();
        }
        return baos.toByteArray();
    }

    public Challenge returnChallenge() {
        String secret = HelperFunctions.randomString(6);
        return new Challenge(shadowText(secret),"png",secret.toLowerCase());
    }
}