如何在 Java 中设置 Tesseract OCR？

Question

I am working on a pretty simple Java project in Visual Studio Code which requires the use of some basic optical character recognition, but I don't have any real experience in setting up APIs or accessing third party software in my code. I'm using Maven to access a Tesseract package from Sourceforge and I got access to a Tesseract class (API?) which takes in a file path (which I believe is used to access the C++ side of things). I used homebrew to install Tesseract and it gave me the file path:

/usr/local/Cellar/tesseract/4.1.1

but when I plug that into this

Tesseract instance = new Tesseract();
instance.setDatapath("/usr/local/Cellar/tesseract/4.1.1");

and run the doOCR method it always results in the same Null-Pointer errors, which makes me think that it isn't correctly accessing Tesseract- especially because the same errors will appear regardless of the file path I input. These are the errors...

21:25:56.021 [main] ERROR net.sourceforge.tess4j.Tesseract - null
java.lang.NullPointerException: null
        at net.sourceforge.tess4j.Tesseract.dispose(Tesseract.java:819)
        at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:239)
        at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:194)
        at com.liamross.tess4j.TessClass.main(TessClass.java:14)
Exception in thread "main" net.sourceforge.tess4j.TesseractException: java.lang.NullPointerException
        at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:245)
        at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:194)
        at com.liamross.tess4j.TessClass.main(TessClass.java:14)
Caused by: java.lang.NullPointerException
        at net.sourceforge.tess4j.Tesseract.dispose(Tesseract.java:819)
        at net.sourceforge.tess4j.Tesseract.doOCR(Tesseract.java:239)

I followed this article as closely as I could, but no matter what I always receive these errors. Also, it seems that there is another directory or library called libtesseract? I'm not quite sure what that's used for or if it's something that I would need...

I know this is a bit of an ambitious project for someone who doesn't have a ton of experience, but any help would be greatly appreciated - I've put a lot of time into trying to figure this out and there doesn't seem to be much comprehensible material about this. Here's a screenshot of what I have so far

Thanks!

Answer 1

I've reproduced your project and at the first time, the same error shown. That's because the Tesseract version is not compatible. Here is the solution:

1. Install the Tesseract4 . My machine is Win10-64bit, so i installed tesseract-ocr-w64-setup-v4.0.0.20181030.exe . Make sure it's installed successfully.

2. Cleaning the Java Language Server Worspace in VS Code, then run again.

Pay attention to the path of tessdata and . jpg file.

Set instance.setHocr(false) to make sure the content was read correctly:

instance.setHocr(true) will show you xml code: