优化

app/src/main/assets/web/help/md/ruleHelp.md

@@ -205,5 +205,42 @@ let options = {
 > 适用于图片需要二次解密的情况，直接填写JavaScript，返回解密后的`ByteArray`  
 > 部分变量说明：java（仅支持[js扩展类](https://github.com/gedoor/legado/blob/master/app/src/main/java/io/legado/app/help/JsExtensions.kt)），result为待解密图片的`ByteArray`，src为图片链接
 
+```
+java.createSymmetricCrypto("AES/CBC/PKCS5Padding", key, iv).decrypt(result)
+```
+
+```
+function decodeImage(data, key) {
+  var input = new Packages.java.io.ByteArrayInputStream(data)
+  var out = new Packages.java.io.ByteArrayOutputStream()
+  var byte
+  while ((byte = input.read()) != -1) {
+    out.write(byte ^ key)
+  }
+  return out.toByteArray()
+}
+
+decodeImage(result, key)
+```
+
 * 封面解密
 > 同图片解密 其中result为待解密封面的`inputStream`
+
+```
+var out = new Packages.java.io.ByteArrayOutputStream()
+java.createSymmetricCrypto("AES/CBC/PKCS5Padding", key, iv).decrypt(data, out, true)
+out.toByteArray()
+```
+
+```
+function decodeImage(data, key) {
+  var out = new Packages.java.io.ByteArrayOutputStream()
+  var byte
+  while ((byte = data.read()) != -1) {
+    out.write(byte ^ key)
+  }
+  return out.toByteArray()
+}
+
+decodeImage(result, key)
+```