EasyCaptcha/src/main/java/com/wf/captcha/SimpleArithmeticCaptcha.java

package com.wf.captcha;

import com.wf.captcha.base.ArithmeticCaptchaAbstract;

import javax.imageio.ImageIO;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Description：最后一位计算时保证结果为正，避免负号输入
 * 2位3位整数计算比较好,否则最后一位会数字会有点异常
 *
 * @author Li Haoran
 */
public class SimpleArithmeticCaptcha extends ArithmeticCaptchaAbstract {

    public SimpleArithmeticCaptcha() {
    }

    public SimpleArithmeticCaptcha(int width, int height) {
        this();
        setWidth(width);
        setHeight(height);
    }

    public SimpleArithmeticCaptcha(int width, int height, int len) {
        this(width, height);
        setLen(len);
    }

    public SimpleArithmeticCaptcha(int width, int height, int len, Font font) {
        this(width, height, len);
        setFont(font);
    }

    public SimpleArithmeticCaptcha(int width, int height, int len, int  font) throws IOException, FontFormatException {
        this(width, height, len);
        setFont(font,32f);
    }

    /**
     * 生成验证码
     *
     * @param out 输出流
     * @return 是否成功
     */
    @Override
    public boolean out(OutputStream out) {
        checkAlpha();
        return graphicsImage(getArithmeticString().toCharArray(), out);
    }

    @Override
    public String toBase64() {
        return toBase64("data:image/png;base64,");
    }

    /**
     * 生成验证码图形
     *
     * @param strs 验证码
     * @param out  输出流
     * @return boolean
     */
    private boolean graphicsImage(char[] strs, OutputStream out) {
        try {
            BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2d = (Graphics2D) bi.getGraphics();
            // 填充背景
            g2d.setColor(Color.WHITE);
            g2d.fillRect(0, 0, width, height);
            // 抗锯齿
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            // 画干扰圆
            drawOval(2, g2d);
            // 画字符串
            g2d.setFont(getFont());
            FontMetrics fontMetrics = g2d.getFontMetrics();
            int fW = width / strs.length;  // 每一个字符所占的宽度
            int fSp = (fW - (int) fontMetrics.getStringBounds("8", g2d).getWidth()) / 2;  // 字符的左右边距
            for (int i = 0; i < strs.length; i++) {
                g2d.setColor(color());
                int fY = height - ((height - (int) fontMetrics.getStringBounds(String.valueOf(strs[i]), g2d).getHeight()) >> 1);  // 文字的纵坐标
                g2d.drawString(String.valueOf(strs[i]), i * fW + fSp + 3, fY - 3);
            }
            g2d.dispose();
            ImageIO.write(bi, "png", out);
            out.flush();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return false;
    }

    /**
     * 生成随机验证码
     * 不包含乘法、没有负数
     * @return 验证码字符数组
     */
    @Override
    protected char[] alphas() {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < len-1; i++) {
            sb.append(num(difficulty));
            if (i < len - 1) {
                int type = num(1, 3);
                if (type == 1) {
                    sb.append("+");
                } else if (type == 2) {
                    sb.append("-");
                }
            }
        }
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("javascript");
        try {
            chars = String.valueOf(engine.eval(sb.toString()));
        } catch (ScriptException e) {
            e.printStackTrace();
        }

        int parseInt = Integer.parseInt(chars);
        if(parseInt<0){
            sb.append("+");
            sb.append(num(-parseInt,-parseInt+11));
        }else {
            int type = num(1, 3);
            if (type == 1) {
                sb.append("+");
                sb.append(num(difficulty));
            } else if (type == 2) {
                sb.append("-");
                sb.append(num(0,parseInt+1));
            }
        }

        try {
            chars = String.valueOf(engine.eval(sb.toString()));
        } catch (ScriptException e) {
            e.printStackTrace();
        }

        sb.append("=?");
        setArithmeticString(sb.toString());
        return chars.toCharArray();
    }

}