基于百度AI实现车牌识别

末蓝、 2022-01-31 01:17 670阅读 0赞

最近做一个需求，希望能通过车牌的图片识别出车牌号，听说百度AI功能挺完善的，本人就想着先做个demo出来验证一下识别的准确性。

1.首先我们要在百度智能云注册个账号。  地址：[https://login.bce.baidu.com/?account=][https_login.bce.baidu.com_account]

2.然后右上角的用户中心--》实名认证里去刷脸认证（该步骤必须要，不然权限不够，调接口会报：No permission to access data）

![20190515111115204.png][]![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70][]

3.创建一个应用

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70 1][]

会生成我们要用到的AppID，API KEY, Secret Key。

![20190515111758889.png][]

百度云AI识别环境弄好了，接下来我们去撸代码

4.pom.xml引入依赖  。 想查看百度云AI的sdk版本的请向这看----》  [https://mvnrepository.com/artifact/com.baidu.aip/java-sdk][https_mvnrepository.com_artifact_com.baidu.aip_java-sdk]

<dependency>
                <groupId>com.baidu.aip</groupId>
                <artifactId>java-sdk</artifactId>
                <version>4.11.0</version>
            </dependency>

5.获取Access\_token，注意更换你的app key和secrot key

package Utils;
    
    import org.json.JSONObject;
    
    import java.io.BufferedReader;
    import java.io.InputStreamReader;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.List;
    import java.util.Map;
    
    public class Access_token {
    
        /**
         * 获取权限token
         * @return 返回示例：
         * {
         * "access_token": "24.460da4889caad24cccdb1fea17221975.2592000.1491995545.282335-1234567",
         * "expires_in": 2592000
         * }
         */
        public static String getAuth() {
            // 官网获取的 API Key 更新为你注册的
            String clientId = "*****";
            // 官网获取的 Secret Key 更新为你注册的
            String clientSecret = "**********";
            return getAuth(clientId, clientSecret);
        }
    
        /**
         * 获取API访问token
         * 该token有一定的有效期，需要自行管理，当失效时需重新获取.
         * @param ak - 百度云官网获取的 API Key
         * @param sk - 百度云官网获取的 Securet Key
         * @return assess_token 示例：
         * "24.460da4889caad24cccdb1fea17221975.2592000.1491995545.282335-1234567"
         */
        public static String getAuth(String ak, String sk) {
            // 获取token地址
            String authHost = "https://aip.baidubce.com/oauth/2.0/token?";
            String getAccessTokenUrl = authHost
                    // 1. grant_type为固定参数
                    + "grant_type=client_credentials"
                    // 2. 官网获取的 API Key
                    + "&client_id=" + ak
                    // 3. 官网获取的 Secret Key
                    + "&client_secret=" + sk;
            try {
                URL realUrl = new URL(getAccessTokenUrl);
                // 打开和URL之间的连接
                HttpURLConnection connection = (HttpURLConnection) realUrl.openConnection();
                connection.setRequestMethod("GET");
                connection.connect();
                // 获取所有响应头字段
                Map<String, List<String>> map = connection.getHeaderFields();
                // 遍历所有的响应头字段
                for (String key : map.keySet()) {
                    System.err.println(key + "--->" + map.get(key));
                }
                // 定义 BufferedReader输入流来读取URL的响应
                BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                String result = "";
                String line;
                while ((line = in.readLine()) != null) {
                    result += line;
                }
                /**
                 * 返回结果示例
                 */
                System.err.println("result:" + result);
                JSONObject jsonObject = new JSONObject(result);
                String access_token = jsonObject.getString("access_token");
                return access_token;
            } catch (Exception e) {
                System.err.printf("获取token失败！");
                e.printStackTrace(System.err);
            }
            return null;
        }
    }

6.创建一个Controller添加方法

/**
         * 获取百度AI应用数据.
         *
         * @return message
         */
        @CrossOrigin
        @RequestMapping(value = "/baidu1", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
        @ResponseBody
        public Map getAisss() {
            Map<String,Object> map1 = new HashMap<>();
            // 获取token
            String accessToken = Access_token.getAuth();
            // 通用识别url
            String otherHost = "https://aip.baidubce.com/rest/2.0/ocr/v1/accurate_basic";
            try {
                //读取本地图片输入流
                FileInputStream inputStream = new FileInputStream("F:/ch1.png");
                String base = Base64.encodeBase64String(IOUtils.toByteArray(inputStream));
                logger.info(base);
                String params = URLEncoder.encode("image", "UTF-8") + "=" + URLEncoder.encode(base, "UTF-8");
                /**
                 * 线上环境access_token有过期时间， 客户端可自行缓存，过期后重新获取。
                 */
    //            String accessToken = "#####调用鉴权接口获取的token#####";
                String result = HttpUtil.post(otherHost, accessToken, params);
                JSONObject jsonObject = JSONObject.parseObject(result);
                JSONArray words_result = (JSONArray) jsonObject.get("words_result");
                JSONObject o = (JSONObject)words_result.get(0);
                map1.put("lincens",o.get("words"));
                System.out.println(result);
            } catch (Exception e) {
                e.printStackTrace();
            }
    
            return map1;
        }

7.工具类（补充代码）

/**
     * http 工具类
     */
    public class HttpUtil {
    
        public static String post(String requestUrl, String accessToken, String params)
                throws Exception {
            String contentType = "application/x-www-form-urlencoded";
            return HttpUtil.post(requestUrl, accessToken, contentType, params);
        }
    
        public static String post(String requestUrl, String accessToken, String contentType, String params)
                throws Exception {
            String encoding = "UTF-8";
            if (requestUrl.contains("nlp")) {
                encoding = "GBK";
            }
            return HttpUtil.post(requestUrl, accessToken, contentType, params, encoding);
        }
    
        public static String post(String requestUrl, String accessToken, String contentType, String params, String encoding)
                throws Exception {
            String url = requestUrl + "?access_token=" + accessToken;
            return HttpUtil.postGeneralUrl(url, contentType, params, encoding);
        }
    
        public static String postGeneralUrl(String generalUrl, String contentType, String params, String encoding)
                throws Exception {
            URL url = new URL(generalUrl);
            // 打开和URL之间的连接
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            // 设置通用的请求属性
            connection.setRequestProperty("Content-Type", contentType);
            connection.setRequestProperty("Connection", "Keep-Alive");
            connection.setUseCaches(false);
            connection.setDoOutput(true);
            connection.setDoInput(true);
    
            // 得到请求的输出流对象
            DataOutputStream out = new DataOutputStream(connection.getOutputStream());
            out.write(params.getBytes(encoding));
            out.flush();
            out.close();
    
            // 建立实际的连接
            connection.connect();
            // 获取所有响应头字段
            Map<String, List<String>> headers = connection.getHeaderFields();
            // 遍历所有的响应头字段
            for (String key : headers.keySet()) {
                System.err.println(key + "--->" + headers.get(key));
            }
            // 定义 BufferedReader输入流来读取URL的响应
            BufferedReader in = null;
            in = new BufferedReader(
                    new InputStreamReader(connection.getInputStream(), encoding));
            String result = "";
            String getLine;
            while ((getLine = in.readLine()) != null) {
                result += getLine;
            }
            in.close();
            System.err.println("result:" + result);
            return result;
        }
    
    }

debugger会发现车牌号识别出来了

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70 2][]

需要注意的地方：

1.图片尽量小，图片流传输比较耗时；

2.`access_token`的有效期为30天，需要每30天进行定期更换；

3.每天的调用次数是有限制的，具体自己看文档；

4.官方文档说明：URL长度不超过1024字节，URL对应的图片base64编码后大小不超过4M，最短边至少15px，最长边最大4096px,支持jpg/jpeg/png/bmp格式，当image字段存在时url字段失效  
请注意关闭URL防盗链

最后奉上github地址：[https://github.com/xiatengGG/SpringBoot-BaiduAI][https_github.com_xiatengGG_SpringBoot-BaiduAI]

[https_login.bce.baidu.com_account]: https://login.bce.baidu.com/?account=
[20190515111115204.png]: https://img-blog.csdnimg.cn/20190515111115204.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70]: /images/20220131/1b1058684ad34933840666b53f657dcc.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70 1]: /images/20220131/7de5cf4788b54fcea53b6ac3ec498c4c.png
[20190515111758889.png]: /images/20220131/8be25d6498274540860ffaf012b267fa.png
[https_mvnrepository.com_artifact_com.baidu.aip_java-sdk]: https://mvnrepository.com/artifact/com.baidu.aip/java-sdk
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDM3NDc4_size_16_color_FFFFFF_t_70 2]: /images/20220131/637c33c0988647c19fd21ffd67d34fc4.png
[https_github.com_xiatengGG_SpringBoot-BaiduAI]: https://github.com/xiatengGG/SpringBoot-BaiduAI