Thank you very much, I'll try all suggested changes. I have already tried
borders
and they seem to work!
Yuliana
On Tuesday, October 16, 2018 at 9:04:04 AM UTC+3, zdenop wrote:
>
>
> 1. If you have quality problem - it good to play with tesseract
> executable instead of API ;-)
> 2. It is know that passing text (in your case just one letter) is not
> best idea - please try to add small white border e.g. 10 px
> 3. Please set dpi for image after SetImage
>
> See attachment for improved images.
> $ tesseract.char_4_b.png - --psm 10 -c page_separator=""
> 4
>
> For single character recognition legacy engine is better and it can
> process your images without modification (but rules above are generally
> good to follow!):
> $ tesseract char_0.png - --psm 10 --oem 0 --dpi 800 -c page_separator=""
> 0
>
> $ tesseract char_4.png - --psm 10 --oem 0 --dpi 800 -c page_separator=""
> 4
>
> $ tesseract char_h.png - --psm 10 --oem 0 --dpi 800 -c page_separator=""
> h
>
> Zdenko
>
>
> po 15. 10. 2018 o 22:44 'Yuliana Zigangirova' via tesseract-ocr <
> tesser...@googlegroups.com <javascript:>> napísal(a):
>
>> Hi everyone,
>>
>> I am trying to use Tesseract for single character recognizing and the
>> results are awful.
>> "h" is recognized as "n", "4" as "/i", "O" as "()";
>>
>> [image: 1testtiff.png]
>>
>> [image: 6testtiff.png]
>>
>>
>> [image: 2testtiff.png]
>>
>>
>>
>> Single character mode seems not to act, as many characters are recognized
>> as two characters,
>> not just one. My images are simple bilevel black and white TIFF images,
>> latin characters. This is bitmap font, not scanned images, they are
>> absolutely clean and
>> need no improvement.
>> Оnly about half of the characters are correctly recognized, which seems
>> to be
>> a very low percent for such a simple task.
>>
>> The library Tesseract version I am using is "4.0.0-beta.3".
>> This is how I call Tesseract.
>>
>> int CharRecognizer::recognizeTIFFData(char* data, int datalength){
>> char *outText;
>> TessBaseAPI* api = new TessBaseAPI();
>> // Initialize tesseract-ocr with English, without specifying
>> tessdata path
>> if (api->Init(NULL, "deu")) {
>> fprintf(stderr, "Could not initialize tesseract.\n");
>> exit(1);
>> }
>> api->SetPageSegMode(tesseract::PSM_SINGLE_CHAR);
>> Pix *image = pixReadMem(data,datalength);
>> api->SetImage(image);
>> // Get OCR result
>> outText = api->GetUTF8Text();
>> printf("\nOCR output:\n%s", outText);
>> // Destroy used object and release memory
>> int utf8 = outText[0];
>> api->End();
>> delete[] outText;
>> pixDestroy(&image);
>> return utf8;
>> }
>>
>> I am new to Tesseract, so probably I am missing something. Do I have to
>> somehow train
>> the library first? May be I should set another OcrEngineMode? I have
>> expected no
>> problems with simple bitmap font recognizing and am quite at lost now.
>> Thank you very much in advance,
>> Yuliana
>>
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