Windows 64位上的Tess4j：多线程上的异常

时间：2014-07-17 08:56:23

标签： java multithreading tesseract ghost4j tess4j

我在Windows 64位上使用带有Java 8的tesseract 3到OCR扫描的PDF。我已经关注instructions on the Tess4j page并使用了所需DLL的64位版本，并安装了64位Ghostscript。

当我使用正常的@Test（无参数）运行我的单元测试时，代码正确运行，所以我想我已经正确安装了所有内容。

当我并行运行2个线程时（见下文），我得到一个例外。

我已经阅读了相关的帖子here，但建议使用我正在使用的Tesseract1（我已尝试过）。

有什么想法吗？

这是代码：

//  @Test // works
@Test(invocationCount = 2, threadPoolSize = 2)
public void testOcr() throws OcrException, TesseractException {
    File scannedPdf = new File(this.getClass().getClassLoader().getResource("scanned.pdf").getFile());
//  Tesseract instance = Tesseract.getInstance();  // JNA Interface Mapping
    Tesseract1 instance = new Tesseract1(); // JNA Direct Mapping
    String str = instance.doOCR(scannedPdf);
    System.out.println("OCR Result: " + str);
}

这是一个例外：

log4j:WARN No appenders could be found for logger (org.ghost4j.Ghostscript).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Ιουλ 16, 2014 6:22:23 ΜΜ net.sourceforge.vietocr.PdfUtilities convertPdf2Png
SEVERE: Cannot initialize Ghostscript interpreter. Error code is -21
org.ghost4j.GhostscriptException: Cannot initialize Ghostscript interpreter. Error code is -21
    at org.ghost4j.Ghostscript.initialize(Ghostscript.java:365)
    at net.sourceforge.vietocr.PdfUtilities.convertPdf2Png(Unknown Source)
    at net.sourceforge.vietocr.PdfUtilities.convertPdf2Tiff(Unknown Source)
    at net.sourceforge.vietocr.ImageIOHelper.getIIOImageList(Unknown Source)
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at OcrUtilsTest.testOcr(OcrUtilsTest.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.internal.thread.ThreadUtil$2.call(ThreadUtil.java:64)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

java.lang.Error: Invalid memory access
    at com.sun.jna.Native.invokeInt(Native Method)
    at com.sun.jna.Function.invoke(Function.java:383)
    at com.sun.jna.Function.invoke(Function.java:315)
    at com.sun.jna.Library$Handler.invoke(Library.java:212)
    at com.sun.proxy.$Proxy3.gsapi_init_with_args(Unknown Source)
    at org.ghost4j.Ghostscript.initialize(Ghostscript.java:350)
    at net.sourceforge.vietocr.PdfUtilities.convertPdf2Png(Unknown Source)
    at net.sourceforge.vietocr.PdfUtilities.convertPdf2Tiff(Unknown Source)
    at net.sourceforge.vietocr.ImageIOHelper.getIIOImageList(Unknown Source)
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at OcrUtilsTest.testOcr(OcrUtilsTest.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.internal.thread.ThreadUtil$2.call(ThreadUtil.java:64)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
net.sourceforge.tess4j.TesseractException: javax.imageio.IIOException: I/O error reading header!
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at net.sourceforge.tess4j.Tesseract1.doOCR(Unknown Source)
    at OcrUtilsTest.testOcr(OcrUtilsTest.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.internal.thread.ThreadUtil$2.call(ThreadUtil.java:64)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javax.imageio.IIOException: I/O error reading header!
    at com.sun.media.imageioimpl.plugins.tiff.TIFFImageReader.readHeader(TIFFImageReader.java:224)
    at com.sun.media.imageioimpl.plugins.tiff.TIFFImageReader.locateImage(TIFFImageReader.java:231)
    at com.sun.media.imageioimpl.plugins.tiff.TIFFImageReader.getNumImages(TIFFImageReader.java:279)
    at net.sourceforge.vietocr.ImageIOHelper.getIIOImageList(Unknown Source)
    ... 18 more
Caused by: java.io.EOFException
    at javax.imageio.stream.ImageInputStreamImpl.readShort(ImageInputStreamImpl.java:229)
    at javax.imageio.stream.ImageInputStreamImpl.readUnsignedShort(ImageInputStreamImpl.java:242)
    at com.sun.media.imageioimpl.plugins.tiff.TIFFImageReader.readHeader(TIFFImageReader.java:199)
    ... 21 more

更新：它似乎与this相关。

1 个答案:

答案 0 :(得分：6)

Tesseract本身只能将图像转换为文本，而不是PDF，即使扫描PDF也是如此。

在幕后，Tess4j使用Ghostscript（通过ghost4j）将每个页面转换为单个图像文件，然后将其提供给Tesseract进行OCR。它将结果字符串连接成一个字符串，然后返回。

异常的原因是Tess4j以不支持多线程的方式使用Ghost4j。如上所述here，ghost4j 从其高级API提供多线程支持（实际上它分别运行不同的Ghostscript实例，每个实例从不同的JVM调用）。但是，Tess4j使用其低级API，可以使用单个Ghostscript实例。

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