if I didn't research how would I know Tesseract needs image processing? I
am new to OCR and in the learning phase please be kind and help thanks :)
On Saturday, January 27, 2024 at 3:26:40 PM UTC+5 zdenop wrote:
> What about reading docs and a little bit googling?
>
> tesseract two-page-passport-mrz-detected.jpeg - --psm 6 -l mrz
>
> IDAUT10000999<6<<<<<<<<<<<<<<<
> 7109094F1112315AUT<<<<<<<<<<<6
> MUSTERFRAU<<ISOLDE<<<<<<<<<<<<
>
>
> Zdenko
>
>
> so 27. 1. 2024 o 11:19 sara waheed <sarawah...@gmail.com> napísal(a):
>
>> I am trying to read the passport mrz string from the image i am using
>> Tesseract and OpenCV for image processing i have tried three different ways
>> none of them worked
>>
>> **Attempt 1**
>> I have this image when i do ocr on it teseract read as
>>
>> IDAUT10000999<6<<<<<<<<<<<<<<<
>> 7109094F1112315AUT<<<<<<xcc<<6
>> MUSTERFRAU<<ISOLDE<<<<<<<<cc<<
>>
>> which is incorrect it treats <<< as x or c or k when I use the `mrz-java`
>> library to read the details from the string it gives the following error
>>
>> [error] Error parsing MRZ string: Failed to parse MRZ MRTD_TD1
>> IDAUT10000999<6<<<<<<<<<<<<<<<
>> [error] 7109094F1112315AUT<<<<<<xcc<<6
>> [error] MUSTERFRAU<<ISOLDE<<<<<<<<cc<<
>> [error] at 24-25,1: Invalid character in MRZ record: x
>>
>> **Attempt 2**
>>
>> then I converted the image to grayscale and binarized it using `OpenCV`
>> Here is the below code
>>
>> val roiImagePath =
>> "src/main/resources/ocr/passport/two-page-passport-mrz-detected.jpeg"
>>
>> val grayScaleROI = new Mat()
>> val roiImage = Imgcodecs.imread(roiImagePath)
>> Imgproc.cvtColor(roiImage, grayScaleROI, Imgproc.COLOR_BGR2GRAY)
>> val roiGaryImagePath =
>> "src/main/resources/ocr/passport/two-page-passport-mrz-detected-gray.jpeg"
>>
>> Imgcodecs.imwrite(roiGaryImagePath, grayScaleROI)
>> val binary = new Mat()
>> Imgproc.adaptiveThreshold(grayScaleROI, binary, 255,
>> Imgproc.ADAPTIVE_THRESH_MEAN_C, Imgproc.THRESH_BINARY , 15, 25)
>> val roiBinaryImagePath =
>> "src/main/resources/ocr/passport/two-page-passport-mrz-detected-binary.jpeg"
>> Imgcodecs.imwrite(roiBinaryImagePath, binary)
>>
>> val tesseract = new Tesseract()
>> tesseract.setDatapath("/usr/share/tesseract-ocr/4.00/tessdata")
>> tesseract.setVariable("user_defined_dpi", "600")
>> val result = tesseract.doOCR(new File(roiBinaryImagePath))
>> val mrzStr = result.replace(" ", "")
>> println(s"two page passport mrz string is: "+mrzStr)
>>
>> it created the following binary image
>>
>> and the code output is
>> tesseract reads mrz string from the binary image as
>>
>> IDAUT1DODD999<E<KK<KKKKEKEKEK
>> 7AD9D9GF1TEZSISAUTKKKKKKKKKEKG
>> MUSTERFRAUSKISOLDEKKKKKKKKKKK
>> and `mrz-java` reads the string and generates the following error
>>
>> [error] Error parsing MRZ string: Failed to parse MRZ null
>> IDAUT1DODD999<E<KK<KKKKEKEKEK
>> [error] 7AD9D9GF1TEZSISAUTKKKKKKKKKEKG
>> [error] MUSTERFRAUSKISOLDEKKKKKKKKKKK
>> [error] at 0-0,0: Different row lengths: 0: 29 and 1: 30
>>
>> **Attempt 3**
>>
>> then I resized the image
>>
>> Val width = 1000 // Increase width proportionately (adjust based on
>> your needs)
>> val height = (width * binary.rows()) / binary.cols() // Maintain
>> aspect ratio
>>
>> val resizedRoiImage = new Mat()
>> Imgproc.resize(binary, resizedRoiImage, new Size(width, height),
>> 0.0, 0.0, Imgproc.INTER_NEAREST)
>>
>> val resizedImageROIPath =
>>
>> "src/main/resources/ocr/passport/two-page-passport-mrz-detected-binary-resized_image.jpg"
>> Imgcodecs.imwrite(resizedImageROIPath, resizedRoiImage)
>>
>> mrz string read by Tesseract
>>
>> TOAUTIOOOOIISKhcceccccddddddce
>> FIOPOSAFIFESSISAUTReececeececs
>> MUSTERFRAUCCKISOLDECKccccdcddd
>>
>> and the error is
>>
>> [info] 15:54:04.200 633 [main] MrzParser INFO - Check digit
>> verification failed for document number: expected 0 but got h
>> [error] Error parsing MRZ string: Failed to parse MRZ MRTD_TD1
>> TOAUTIOOOOIISKhcceccccddddddce
>> [error] FIOPOSAFIFESSISAUTReececeececs
>> [error] MUSTERFRAUCCKISOLDECKccccdcddd
>> [error] at 15-16,0: Invalid character in MRZ record: c
>>
>>
>> can anyone please help how I read the text properly also I have tried one
>> regex to convert c or k back to <<< it did not work either if anyone can
>> suggest some workaround or any improvement in code please help me with that
>> thanks
>>
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