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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