JAVA OCR Tesseract recognition code implementation

Others 2022-04-20 18:11:26 views: 0

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Introduction to Tesseract OCR

Tesseract's OCR engine was first developed by HP Labs in 1985, and by 1995 it had become one of the three most accurate recognition engines in the OCR industry. However, HP soon decided to give up the OCR business, and Tesseract has been in the dust ever since.

A few years later, HP realized that instead of putting Tesseract on the shelf, it was better to contribute to the open source software industry and bring it back to life - in 2005, Tesseract was acquired by the Nevada Institute of Information Technology, and asked Google to improve Tesseract , Eliminate bugs, optimize work.

After fixing the most important bugs, Google believes that Tesseract OCR is stable enough to be re-released as open source software.

Tesseract GitHub address

1 Installation test under Windows

If vc 2015 is not installed, there will be errors such as gs not found

If the environment variable is not configured, an Please make sure the TESSDATA_PREFIX environment variable is set to the parent directory of your "tessdata" directoryerror

0x80240017If there is an -unspecified error when installing vc 2015 , please refer to here to solve

  • Test using the command line
:: cd 到对应目录

tesseract sourcefile.jpg savename -l chi_sim

2. Installation test under MacOS

Just use Homebrewinstall tesseract, brew will automatically install the dependencies.

    brew install tesseract
  • Test using the command line
tesseract sourcefile.jpg savename -l chi_sim

3. JAVA environment

3.1 Development Environment

  • JDK 1.8
  • IDEA 2017
  • junit 4.2
  • log4j2
  • Maven3.x

3.2 pom.xml

If it is not a maven project, skip this step

<properties>
      <java.version>1.8</java.version>
      <log4j2.version>2.1</log4j2.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.12</version>
         <scope>test</scope>
      </dependency>

      <!--日志包-->
      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-core</artifactId>
         <version>${log4j2.version}</version>
      </dependency>
      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-api</artifactId>
         <version>${log4j2.version}</version>
      </dependency>
      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-web</artifactId>
         <version>${log4j2.version}</version>
      </dependency>
      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-slf4j-impl</artifactId>
         <version>${log4j2.version}</version>
      </dependency>
      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-jcl</artifactId>
         <version>${log4j2.version}</version>
      </dependency>

      <dependency>
         <groupId>org.apache.directory.studio</groupId>
         <artifactId>org.apache.commons.lang</artifactId>
         <version>2.6</version>
      </dependency>

   </dependencies>

3.3 log4j2.xml

For specific log4j2 configuration, please refer to: Log4j1 upgrade Log4j2 actual combat

<?xml version="1.0" encoding="UTF-8"?>

<Configuration status="warn" monitorInterval="600">

    <Properties>
        
        <property name="BASE_LOG_PATTERN">%5p %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] (%class{36}:%L）%M - %m%n</property>
        <property name="LOG_DIR_HOME">logs</property>
        <property name="BASE_LOG_FILENAME">nuna-ocr</property>
    </Properties>

    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <ThresholdFilter level="trace" onMatch="ACCEPT" onMismatch="DENY" immediateFlush="true"/>
            <PatternLayout pattern="${BASE_LOG_PATTERN}" />
        </Console>

        <RollingRandomAccessFile name="stdout_appender"
                                 immediateFlush="true" fileName="${LOG_DIR_HOME}/${BASE_LOG_FILENAME}-stdout.log"
                                 filePattern="${LOG_DIR_HOME}/${BASE_LOG_FILENAME}-stdout-%d{yyyy-MM-dd}_%i.log.gz">
            <PatternLayout>
                <pattern>${BASE_LOG_PATTERN}</pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy modulate="true" interval="1"/>
                <SizeBasedTriggeringPolicy size="5120 KB"/>
            </Policies>

            <DefaultRolloverStrategy max="3"/>

        </RollingRandomAccessFile>

        <RollingRandomAccessFile name="error_appender"
                                 immediateFlush="true" fileName="${LOG_DIR_HOME}/${BASE_LOG_FILENAME}-error.log"
                                 filePattern="${LOG_DIR_HOME}/${BASE_LOG_FILENAME}-error-%d{yyyy-MM-dd}_%i.log.gz">
            <PatternLayout>
                <pattern>${BASE_LOG_PATTERN}</pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy modulate="true" interval="1"/>
                <SizeBasedTriggeringPolicy size="5120 KB"/>
            </Policies>
            <Filters>
                <ThresholdFilter level="warn" onMatch="ACCEPT" onMismatch="DENY"/>
            </Filters>
            <DefaultRolloverStrategy max="3"/>
        </RollingRandomAccessFile>
    </Appenders>

    <Loggers>
        <logger name="com.liu.app.ocr" level="debug" additivity="false" >
            <appender-ref ref="Console" />
            <appender-ref ref="stdout_appender" />
            <appender-ref ref="error_appender" />
        </logger>

        <root level="info" includeLocation="true">
            <appender-ref ref="Console" />
            <appender-ref ref="stdout_appender" />
            <appender-ref ref="error_appender"/>
        </root>
    </Loggers>

</Configuration>

4. JAVA code implementation


import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang.StringUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class OcrProcess {

    private static Logger logger = LogManager.getLogger(OcrProcess.class);

    private String tessPath = "";

    private String ocr_psm_num = "3";

    private String ocr_language = "eng";

    private String ocr_result_path = "";

    private String ocr_result_file_path = "";

    private final String OS = System.getProperty("os.name");

    private final String ocr_lang_option = "-l";

    public final String ocr_psm_option = "-psm";

    private long procID = 0;

    /**
     * 文本换行符
     */
    private final String EOL = System.getProperty("line.separator");

    /**
     * 当前系统，路径分割符
     */
    private final String FIS = System.getProperties().getProperty("file.separator");

    /**
     * 构造函数
     * @param tessPath 本地 tesseract 路径
     */
    public OcrProcess(String tessPath) {
        this.tessPath = tessPath;

        if(logger.isDebugEnabled()){
            logger.debug("OcrProcess Created .");
            logger.debug("OcrProcess Current OS >>> {} ",this.OS);
            logger.debug("OcrProcess User tessPath >>> {} ",this.tessPath);
        }else if(logger.isInfoEnabled()){
            logger.info("OcrProcess Created .");
        }
    }

    /**
     * 设置 pagesegmode 1-10
     * 0 = Orientation and script detection (OSD) only.
     * 1 = Automatic page segmentation with OSD.
     * 2 = Automatic page segmentation, but no OSD, or OCR.
     * 3 = Fully automatic page segmentation, but no OSD. (Default)
     * 4 = Assume a single column of text of variable sizes.
     * 5 = Assume a single uniform block of vertically aligned text.
     * 6 = Assume a single uniform block of text.
     * 7 = Treat the image as a single text line.  // 识别内容为 横行， 可以提供单行文本的识别效率
     * 8 = Treat the image as a single word.
     * 9 = Treat the image as a single word in a circle.
     * 10 = Treat the image as a single character.
     * @param psm 参考 tesseract 文档
     */
    public void setPageSegMode(Integer psm){

        if(logger.isDebugEnabled()){
            logger.debug("OcrProcess User set OCR Process PageSeqMode >>> {}",psm);
        }else if(logger.isInfoEnabled()){
            logger.info("OcrProcess User set OCR Process PageSeqMode >>> {}",psm);
        }

        if(psm == null){
            throw new IllegalArgumentException("param psm is null,will use default 3");
        }
        if(psm > 10 || psm < 0){
            throw new IllegalArgumentException("param psm only between 0 and 10,will use default 3");
        }

        this.ocr_psm_num = String.valueOf(psm);
    }

    /**
     * 设置保存路径
     * @param savePath
     */
    public void setSaveDir(String savePath) throws FileNotFoundException {

        if(logger.isDebugEnabled()){
            logger.debug("OcrProcess User set OCR Process Result TXT SavePath >>> {}",savePath);
        }else if(logger.isInfoEnabled()){
            logger.info("OcrProcess User set OCR Process Result TXT SavePath >>> {}",savePath);
        }

        File saveDir = new File(savePath);

        if(!saveDir.exists()){
            throw new FileNotFoundException("the savePath is not found!");
        }

        this.ocr_result_path = savePath;

    }

    /**
     *
     * @author alexliu
     * @date：2017年11月22日 下午2:39:42
     * @Description：文件 ocr
     * @param file 文件
     * @param language 语言  chi_sim ,eng
     * @return 识别后文件路径
     * @throws NoSupportFileTypeException 自定义异常
     */
    public String doOCR(File file , String language) throws NoSupportFileTypeException {
        // 创建一个 ocr 执行id，便于日志、数据记录
        //this.procID = OcrTools.createProcessId();
        this.procID = new Random().nextInt(1000);

        if(logger.isDebugEnabled()){
            logger.debug("OcrProcess Begin. The file >>> [{}], the procID is [{}] .",file.getName(),this.procID);
        }else if(logger.isInfoEnabled()){
            logger.info("OcrProcess Begin. The file >>> [{}], the procID is [{}] . See More info PLZ set logger Debug or Trace.",file.getName(),this.procID);
        }

        String textSavePath = "";

        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : FilePath >>> {}",this.procID,file.getAbsolutePath());
            logger.debug("[{}] OCR process info : FileName >>> {}",this.procID,file.getName());
            logger.debug("[{}] OCR process info : FileSize >>> {} KB",this.procID,(file.length() / 1024f));
            logger.debug("[{}] OCR process info : OCR Language >>> {}",this.procID,language);
        }

        this.ocr_language = language;

        //获取文件类型
        int fileType = this.getFileType(file.getName());

        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : FileType >>> {}",this.procID,fileType);
        }
        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : The FileType is Image .",this.procID);
        }
        textSavePath = callTesseractCommand(file);

        return textSavePath;
    }

    /**
     * 获取输出路径
     * 如果 用户调用了 `setSaveDir` ,那么 OCR 输出到用户设置的目录
     * 如果 没有调用 `setSaveDir` ，那么 OCR 输出与识别文件同一目录
     * @param sourceFile 原始文件
     * @return
     */
    private String getOutPutDir(File sourceFile){

        if(StringUtils.isEmpty(this.ocr_result_path)){
            return sourceFile.getAbsolutePath().substring(0,sourceFile.getAbsolutePath().lastIndexOf(this.FIS));
        }

        return this.ocr_result_path;
    }

    /**
     * 获取文件类型
     * @param fileName
     * @return
     * @throws NoSupportFileTypeException 自定义异常
     */
    private Integer getFileType(String fileName) throws NoSupportFileTypeException {

        //此处根据文件后缀名判断是否是可以执行 OCR 的文件类型
        //Integer type = OcrTools.getFileType(fileName);

        Integer type = null;

        if(type == null){
            // NoSupportFileTypeException 为自定义异常，此处可自定义您的内容
            //throw new NoSupportFileTypeException("["+fileName+"] , 无法识别的文件类型.");
        }

        return type;
    }

    /**
     * 创建 ProcessBuilder
     * @param sourceFile
     * @return
     */
    private ProcessBuilder createProcessBuilder(File sourceFile){

        ProcessBuilder pb = new ProcessBuilder();

        if(this.OS.startsWith("Mac OS") || this.OS.startsWith("Linux")){

            //设置命令行工作目录，Linux , Mac OS 设置在 tesseract 目录下
            //因为 tesseract 非安装模式，也没有添加到系统的环境变量中
            pb.directory(new File(this.tessPath));
            if(logger.isDebugEnabled()){
                logger.debug("[{}] OCR process info : Set ProcessBuilder working dir >>> {}",this.procID,this.tessPath);
            }

        }else if(this.OS.startsWith("Windows")){
            //设置命令行工作目录,windows 下设置在要解析的文件目录下
            pb.directory(sourceFile.getParentFile());
            if(logger.isDebugEnabled()){
                logger.debug("[{}] OCR process info : Set ProcessBuilder working dir >>> {}",this.procID,sourceFile.getParentFile());
            }
        }

        //输出错误日志流
        pb.redirectErrorStream(true);

        return pb;
    }

    /**
     * 创建命令行
     * @param sourceFile
     * @return
     */
    private List<String> createCommand(File sourceFile){

        List<String> cmd = new ArrayList<String>();

        //ocr 输出目录
        String result_out_dir = getOutPutDir(sourceFile);

        //ocr 命令输出文件名，没有后缀
        String ocr_result_filename = sourceFile.getName().substring(0 , sourceFile.getName().lastIndexOf("."));

        //ocr 输出文件名,有后缀
        String result_out_filePath = result_out_dir + this.FIS + ocr_result_filename + ".txt";

        this.ocr_result_file_path = result_out_filePath;

        if(logger.isDebugEnabled()) {
            logger.debug("[{}] OCR process info : Result SaveDir >>> {}",this.procID,result_out_dir);
            logger.debug("[{}] OCR process info : Result SaveFilePath >>> {}",this.procID,result_out_filePath);
        }else if(logger.isInfoEnabled()){
            logger.info("[{}] OCR process info : Result SaveFilePath >>> {}",this.procID,result_out_filePath);
        }

        if(this.OS.startsWith("Mac OS") || this.OS.startsWith("Linux")){
            cmd.add("tesseract");
            // Linux or Mac 要设置工作目录为 tesseract 目录 ，所以`原始文件名`需包含路径
            cmd.add(sourceFile.getAbsolutePath());

        }else if(this.OS.startsWith("Windows")){
            cmd.add(this.tessPath + this.FIS + "tesseract");
            // windows 要设置工作目录为文件目录，所以`原始文件名`没有路径，只有文件名
            cmd.add(sourceFile.getName());
        }

        cmd.add(result_out_dir + this.FIS + ocr_result_filename);
        cmd.add(this.ocr_psm_option);
        cmd.add(this.ocr_psm_num);
        cmd.add(this.ocr_lang_option);
        cmd.add(this.ocr_language);

        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : The Command >>> {}",this.procID,cmd.toString());
        }else if(logger.isInfoEnabled()){
            logger.info("[{}] OCR process info : The Command >>> {}",this.procID,cmd.toString());
        }

        return cmd;
    }

    /**
     * 处理识别后的空格字符
     * @param txtFilePath
     * @throws FileNotFoundException
     */
    private void processSpace(String txtFilePath) throws FileNotFoundException {

        FileInputStream fis = null;
        InputStreamReader isr = null;
        BufferedReader br = null;
        String str;

        FileOutputStream fos = null;
        OutputStreamWriter osw = null;
        BufferedWriter bw = null;

        boolean readSuccess = true;

        File txtFile = new File(txtFilePath);

        if(!txtFile.exists()){
            throw new FileNotFoundException("OCR process Result file is not exist!");
        }

        StringBuilder sb = new StringBuilder();

        try {
            //读取文件
            fis = new FileInputStream(txtFile);
            isr = new InputStreamReader(fis,"UTF-8");
            br = new BufferedReader(isr);

            while ((str = br.readLine()) != null) {
                sb.append(str).append(this.EOL);
            }
        } catch (Exception e){
            logger.error("[{}] OCR process space read file faild .",this.procID,e);
            readSuccess = false;
        } finally {
            try {
                br.close();
            }catch (Exception e){
                //ignore;
            }
            try {
                isr.close();
            }catch (Exception e){
                //ignore;
            }
            try {
                fis.close();
            }catch (Exception e){
                //ignore;
            }
        }

        //处理空格
        if(readSuccess){
            try {
                //写出文件
                fos = new FileOutputStream(txtFile);
                osw = new OutputStreamWriter(fos,"UTF-8");
                bw = new BufferedWriter(osw);
                bw.write(sb.toString().replaceAll(" ", ""));
            } catch (Exception e){
                logger.error("[{}] OCR process space write file faild .",this.procID,e);
            } finally {
                try {
                    bw.close();
                }catch (Exception e){
                    //ignore;
                }
                try {
                    osw.close();
                }catch (Exception e){
                    //ignore;
                }
                try {
                    fos.close();
                }catch (Exception e){
                    //ignore;
                }
            }
        }
    }

    /**
     * 打印命令行执行错误日志
     * @param process
     */
    private void printCommandError(Process process){
        InputStream fis = null;
        InputStreamReader isr = null;
        BufferedReader br = null;
        try {
            // 取得命令结果的输出流
            fis = process.getInputStream();
            // 用一个读输出流类去读
            isr = new InputStreamReader(fis);
            // 用缓冲器读行
            br = new BufferedReader(isr);
            String line = null;
            // 直到读完为止
            while ((line = br.readLine()) != null) {
                logger.warn("[{}] OCR process warning : {} ",this.procID,line);
            }
        } catch (Exception e){
            logger.warn("[{}] OCR process print command error Faild!",e);
        } finally {
            try {
                br.close();
            } catch (Exception e){
                //ignore
            }
            try {
                isr.close();
            } catch (Exception e){
                //ignore
            }
            try {
                fis.close();
            } catch (Exception e){
                //ignore
            }
        }
    }

    /**
     *
     * @author alexliu
     * @date：2017年11月22日 下午2:47:25
     * @Description：用命令行执行ocr
     * @param imageFile
     * @return 返回识别后的文件路径目
     * @throws Exception
     */
    private String callTesseractCommand(File imageFile) {

        String txt_path = "";

        List<String> comand = this.createCommand(imageFile);

        ProcessBuilder pb = this.createProcessBuilder(imageFile);

        //添加命令行
        pb.command(comand);

        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : Add command to ProcessBuilder",this.procID);
        }

        Process process = null;
        try {

            if(logger.isDebugEnabled()){
                logger.debug("[{}] OCR process info : Excute OCR Command.",this.procID);
            }
            process = pb.start();

            int w = process.waitFor();
            if(logger.isDebugEnabled()){
                logger.debug("[{}] OCR process info : Command excute result >>> {}",this.procID,w);
            }else if(logger.isInfoEnabled()){
                logger.info("[{}] OCR process info : Command excute result >>> {}",this.procID,w);
            }

            if (w == 0) {
                txt_path = this.ocr_result_file_path;
                //处理空格
                this.processSpace(txt_path);
            } else {
                //打印错误日志
                this.printCommandError(process);
                String msg = "[%s] excute command Faild ! Result %d , Reason : %s !";
                switch (w) {
                    case 1:
                        msg = String.format(msg,this.procID,w,"无法访问文件，可能文件名中存在空格等特殊字符");
                        break;
                    case 29:
                        msg = String.format(msg,this.procID,w,"无法识别图像或其选定区域");
                        break;
                    case 31:
                        msg = String.format(msg,this.procID,w,"不支持的图片格式");
                        break;
                    default:
                        msg = String.format(msg,this.procID,w,"未知错误");
                }
                throw new RuntimeException(msg);
            }

        } catch (IOException e) {
            logger.error("[{}] OCR process info : Command excute [pb.start()] Faild !",this.procID,e);
        } catch (InterruptedException e) {
            logger.error("[{}] OCR process info : Command excute [process.waitFor()] Faild !",this.procID,e);
        }

        if(logger.isDebugEnabled()){
            logger.debug("[{}] OCR process info : OCR Process End.",this.procID);
        }else if(logger.isInfoEnabled()){
            logger.info("[{}] OCR process info : OCR Process End.",this.procID);
        }

        return txt_path;
    }

}

4.1 Testing


import org.apache.logging.log4j.core.config.ConfigurationSource;
import org.apache.logging.log4j.core.config.Configurator;
import org.junit.Before;
import org.junit.Test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class TestFileOCR {

    private static String log4jxml = "/your/log/config/path/log4j2.xml";

    @Before
    public void before() throws FileNotFoundException {
        File config=new File(log4jxml);
        ConfigurationSource source = new ConfigurationSource(new FileInputStream(config),config);
        Configurator.initialize(null, source);
    }

    public void test_JPG_Linux(){
        String tessPath = "/your/tesseract/path/Tesseract-OCR";
        String img = "/your/test/file/path/test.jpg";

        OcrProcess ocr = new OcrProcess(tessPath);

        //测试保存其他目录
//        try {
//            ocr.setSaveDir("/others/save/path");
//        } catch (FileNotFoundException e) {
//            e.printStackTrace();
//        }
        File file = new File(img);
        try {
            String path = ocr.doOCR(file, "chi_sim");
            System.out.println(path);
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    public void test_JPG_Windows(){

        String tessPath = "D:\\your\\tesseract\\path\\Tesseract-OCR";
        String img = "C:\\your\\test\\file\\path\\test.jpg";

        OcrProcess ocr = new OcrProcess(tessPath);
        //测试保存其他目录
        try {
            ocr.setSaveDir("C:\\others\\save\\path");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        File file = new File(img);
        try {
            String path = ocr.doOCR(file, "chi_sim");
            System.out.println(path);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

5. Third-party JARs

If you feel that it is inconvenient to use the command line method, you can use Tess4j, which is introduced by Maven as follows.

<dependency>
    <groupId>net.sourceforge.tess4j</groupId>
    <artifactId>tess4j</artifactId>
    <version>3.4.3</version>
</dependency>

Tess4j enriches image processing on top of tesseract, it can be enlarged and recognized, and there are some learning functions, but during the test process, tess4j consumes more memory than using the command line directly.

6. Practical application

OCR is a particularly memory-consuming operation. It is recommended to deploy components independently and call them through API with your service.

Below is some data from my app, OCR for standalone deployment. for reference only:

  • memory consumption

    1. Open 5 threads to process at the same time, and the memory is maintained between 8-12G.
    2. A single thread is maintained between 3-4G.

  • Recognition efficiency

    1. 100 sheets of A4 paper content, 300kb each, single thread, processing time is 20-24 minutes, 12-16 seconds per sheet
    2. 10000 sheets of A4 paper content, 300kb each, 5 threads, the processing time is 7-10 hours, the probability of failure in the middle will increase, and the number of retries will be increased.

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