java图片识别文字的方法

java文字识别程序的关键是寻找一个可以调用的OCR引擎。tesseract-ocr就是一个这样的OCR引擎，在1985年到1995年由HP实验室开发，现在在Google。tesseract-ocr 3.0发布，支持中文。不过tesseract-ocr 3.0不是图形化界面的客户端，别人写的FreeOCR图形化客户端还不支持导入新的 3.0 traineddata。但这标志着，现在有自由的中文OCR软件了。

java中使用tesseract-ocr3.01的步骤如下：

1.下载安装tesseract-ocr-setup-3.01-1.exe（3.0以上版本才增加了中文识别）

2.在安装向导中可以选择需要下载的语言包。

3.到网上搜索下载java图形处理所需的2个包：jai_imageio-1.1-alpha.jar，swingx-1.6.1.jar

4.java程序清单：

ImageIOHelper 类：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Locale; 

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.stream.ImageInputStream;
import javax.imageio.stream.ImageOutputStream; 

import com.sun.media.imageio.plugins.tiff.TIFFImageWriteParam; 

public class ImageIOHelper { 

 public static File createImage(File imageFile, String imageFormat) {
  File tempFile = null;
  try {
   Iterator readers = ImageIO.getImageReadersByFormatName(imageFormat);
   ImageReader reader = readers.next(); 

   ImageInputStream iis = ImageIO.createImageInputStream(imageFile);
   reader.setInput(iis);
   //Read the stream metadata
   IIOMetadata streamMetadata = reader.getStreamMetadata(); 

   //Set up the writeParam
   TIFFImageWriteParam tiffWriteParam = new TIFFImageWriteParam(Locale.CHINESE);
   tiffWriteParam.setCompressionMode(ImageWriteParam.MODE_DISABLED); 

   //Get tif writer and set output to file
   Iterator writers = ImageIO.getImageWritersByFormatName("tiff");
   ImageWriter writer = writers.next(); 

   BufferedImage bi = reader.read(0);
   IIOImage image = new IIOImage(bi,null,reader.getImageMetadata(0));
   tempFile = tempImageFile(imageFile);
   ImageOutputStream ios = ImageIO.createImageOutputStream(tempFile);
   writer.setOutput(ios);
   writer.write(streamMetadata, image, tiffWriteParam);
   ios.close(); 

   writer.dispose();
   reader.dispose(); 

  } catch (IOException e) {
   e.printStackTrace();
  }
  return tempFile;
 } 

 private static File tempImageFile(File imageFile) {
  String path = imageFile.getPath();
  StringBuffer strB = new StringBuffer(path);
  strB.insert(path.lastIndexOf('.'),0);
  return new File(strB.toString().replaceFirst("(?<=//.)(//w+)$", "tif"));
 } 

} 

OCR 类：

package com.hhp.util; 

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.jdesktop.swingx.util.OS; 

public class OCR {
 private final String LANG_OPTION = "-l"; //英文字母小写l，并非数字1
 private final String EOL = System.getProperty("line.separator");
 private String tessPath = "C://Program Files (x86)//Tesseract-OCR";
 //private String tessPath = new File("tesseract").getAbsolutePath(); 

 public String recognizeText(File imageFile,String imageFormat)throws Exception{
  File tempImage = ImageIOHelper.createImage(imageFile,imageFormat);
  File outputFile = new File(imageFile.getParentFile(),"output");
  StringBuffer strB = new StringBuffer();
  List cmd = new ArrayList();
  if(OS.isWindowsXP()){
   cmd.add(tessPath+"//tesseract");
  }else if(OS.isLinux()){
   cmd.add("tesseract");
  }else{
   cmd.add(tessPath+"//tesseract");
  }
  cmd.add("");
  cmd.add(outputFile.getName());
  cmd.add(LANG_OPTION);
  cmd.add("chi_sim");
  //cmd.add("eng"); 

  ProcessBuilder pb = new ProcessBuilder();
  pb.directory(imageFile.getParentFile()); 

  cmd.set(1, tempImage.getName());
  pb.command(cmd);
  pb.redirectErrorStream(true); 

  Process process = pb.start();
  //tesseract.exe 1.jpg 1 -l chi_sim
  int w = process.waitFor(); 

  //删除临时正在工作文件
  tempImage.delete(); 

  if(w==0){
   BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(outputFile.getAbsolutePath()+".txt"),"UTF-8")); 

   String str;
   while((str = in.readLine())!=null){
    strB.append(str).append(EOL);
   }
   in.close();
  }else{
   String msg;
   switch(w){
    case 1:
     msg = "Errors accessing files.There may be spaces in your image's filename.";
     break;
    case 29:
     msg = "Cannot recongnize the image or its selected region.";
     break;
    case 31:
     msg = "Unsupported image format.";
     break;
    default:
     msg = "Errors occurred.";
   }
   tempImage.delete();
   throw new RuntimeException(msg);
  }
  new File(outputFile.getAbsolutePath()+".txt").delete();
  return strB.toString();
 }
}

测试类TestOCR ：

import java.io.File;
import java.io.IOException; 

import com.hhp.util.OCR; 

public class OcrTest { 

 public static void main(String[] args) {
  String path = "C://temp//OCRcode//4.png";
  System.out.println("ORC Test Begin......");
  try {
   String valCode = new OCR().recognizeText(new File(path), "png");
   System.out.println(valCode);
  } catch (IOException e) {
   e.printStackTrace();
  } catch (Exception e) {
   e.printStackTrace();
  }
  System.out.println("ORC Test End......");
 } 

} 

经过测试，tesseract-ocr 3.01的文字识别率很高，对于网站中常见的验证码识别率也很高。

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