增加内置字体、贝塞尔曲线、算术验证码、base64输出

src/main/java/com/wf/captcha/base/ArithmeticCaptchaAbstract.java

@@ -0,0 +1,55 @@
+package com.wf.captcha.base;
+
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+
+public abstract class ArithmeticCaptchaAbstract extends Captcha {
+    private String arithmeticString;  // 计算公式
+
+    public ArithmeticCaptchaAbstract() {
+        setLen(2);
+    }
+
+    /**
+     * 生成随机验证码
+     *
+     * @return 验证码字符数组
+     */
+    @Override
+    protected char[] alphas() {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < len; i++) {
+            sb.append(num(10));
+            if (i < len - 1) {
+                int type = num(1, 4);
+                if (type == 1) {
+                    sb.append("+");
+                } else if (type == 2) {
+                    sb.append("-");
+                } else if (type == 3) {
+                    sb.append("x");
+                }
+            }
+        }
+        ScriptEngineManager manager = new ScriptEngineManager();
+        ScriptEngine engine = manager.getEngineByName("javascript");
+        try {
+            chars = String.valueOf(engine.eval(sb.toString().replaceAll("x", "*")));
+        } catch (ScriptException e) {
+            e.printStackTrace();
+        }
+        sb.append("=?");
+        arithmeticString = sb.toString();
+        return chars.toCharArray();
+    }
+
+    public String getArithmeticString() {
+        checkAlpha();
+        return arithmeticString;
+    }
+
+    public void setArithmeticString(String arithmeticString) {
+        this.arithmeticString = arithmeticString;
+    }
+}