Whitelist not working

[kylefoley76]

Current Behavior

I'm using Tesseract with Python because it's too difficult to OCR when the languages are mixed between the Greek alphabet and the Latin alphabet. Too often I will get Cyrillic characters as an output. I was hoping that the whitelist feature would solve that problem. But this is not the case. When I input the following whitelist,

αςερτυθιοπλκξηγφδσζχψωβνμΣΕΡΤΥΘΙΟΠΛΚΞΗΓΦΔΣΑΖΧΨΩΒΝΜΑΖΧΨΩΒΝΜABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890/?<>{}*&,;.:-+=|1234567890

I get a reasonably good output for the Latin characters, but the Greek text is not very accurate. for example, here is an output

Contracted nouns and adjectives in -ους from -οος 63
Adjectives of material in -ots from -εος 64
Nouns in ts, -εως and -υς/-υ, -εως 65

But the correct output should be οῦς not -ots

However, even if the accuracy were 100%, that whitelist will not solve my problem because it does not use the diacritics. So when I use a whitelist with diacritics, such as

"ΆᾺΑἉἊἍἋἌᾍᾈᾌᾎᾉAΒΔΗΉἩἨἮἯἬἫἭἪῌᾞᾟᾜᾘᾙῊἜἚἝἛἘἙΈΕΓΙῚἾἿἽἻἺἼἹἸΊIΚΧΞΛΜΝὩὨῼὭὫὬὪὯὮΩΏὉὈὊὋὌὍΟΌῸῺᾨᾩᾯᾮᾪᾫᾬᾭΠΦΨῬΡΣΤΘὝὛὙΎΥὟΖᾅᾳᾇᾄᾂᾀᾷᾆᾴᾲἇἆἂἄἅἃάᾶὰαἁἀααᾁᾃβδέὲἕἓἒἔἑἐεἠῆᾖἧᾔᾐᾑἥἣᾕἡἦῄῂῇᾗηῃήὴἤἢᾒᾓγϊῖιἰἶἴἲἱΐῒὶίἷἵἳῗιικχλμνὁᾦὀοῷὧωὠᾡὦῳῶὡᾠᾧῴῲὢὤὥὣᾤᾢὅὃὄὂόὸώὼᾣᾥπφψῤῥρςστθὖϋὗῧὐὑυῦὔὒύὺὓὕῢΰυυϝξζΑΖΧΨΩΒΝΜABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890/?<>{}*&,;.:-+=|1234567890 "

I get the output:

ΝΕΗΟΓΑΑΠΚ
Α
ΑΟΗΠΓΠΟΠ
ΑΟΕΠΓ
ΑΕΠΓΟ
ΑΠ
ἸΑΓΝΠΑΟΕΕ
ΡΟΡΟΠ
ΑΙΟΓΠΊ
ΠΟΙΠΕΟΓΠΓΕΠΟΏΡΒΡ
ΑΓ Ι
ΙΠΠΠΠΊΒΠ

I've tried locating the characters that are messing things up but there are too many. But it is certainly not any of these characters: /?<>{}*&,;.:-+=|

The image I'm trying to scan is uploaded. here is the exact python code I'm using:

import pytesseract
custom_oem_psm_config = '--oem 3 --psm 6 -c tessedit_char_whitelist="{}"'.format(
"ΆᾺΑἉἊἍἋἌᾍᾈᾌᾎᾉAΒΔΗΉἩἨἮἯἬἫἭἪῌᾞᾟᾜᾘᾙῊἜἚἝἛἘἙΈΕΓΙῚἾἿἽἻἺἼἹἸΊIΚΧΞΛΜΝὩὨῼὭὫὬὪὯὮΩΏὉὈὊὋὌὍΟΌῸῺᾨᾩᾯᾮᾪᾫᾬᾭΠΦΨῬΡΣΤΘὝὛὙΎΥὟΖᾅᾳᾇᾄᾂᾀᾷᾆᾴᾲἇἆἂἄἅἃάᾶὰαἁἀααᾁᾃβδέὲἕἓἒἔἑἐεἠῆᾖἧᾔᾐᾑἥἣᾕἡἦῄῂῇᾗηῃήὴἤἢᾒᾓγϊῖιἰἶἴἲἱΐῒὶίἷἵἳῗιικχλμνὁᾦὀοῷὧωὠᾡὦῳῶὡᾠᾧῴῲὢὤὥὣᾤᾢὅὃὄὂόὸώὼᾣᾥπφψῤῥρςστθὖϋὗῧὐὑυῦὔὒύὺὓὕῢΰυυϝξζΑΖΧΨΩΒΝΜABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890\/?<>{}[]()*&,;.:-+=| "
)
str4 = pytesseract.image_to_string(img1, config=custom_oem_psm_config,lang='eng+ell')
print(str4)

I'm using pytesseract 0.3.13 and I have tesseract 5.3.8 installed. Also chatgpt informs me that sometimes tessearact cannot handle large whitelists. if that is the case then i think it would be very easy to solve that problem.

Expected Behavior

No response

Suggested Fix

No response

tesseract -v

No response

Operating System

No response

Other Operating System

No response

uname -a

No response

Compiler

No response

CPU

No response

Virtualization / Containers

No response

Other Information

No response

[amitdo]

As you found out yourself, currently the whitelist/blacklist feature does not work as expected with the lstm ocr engine. Also, the lang1+lang2 combo does not work well.

[amitdo]

If you only need Greek and English, you can try tesseract in.png out -l Greek.

https://github.com/tesseract-ocr/tessdata_best/tree/main/script

[CanadianHusky]

I have the same problem with german diacritics (umlaute) on windows command line.
There is no way that I could find that allows
-c tessedit_char_whitelist=ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyzÄÖÜßäöü0123456789
part of the problem is that default windows command line does not support utf8
but even from powershell terminal with chcp 65001 or separate config file, I could not get whitelist or blacklist to work properly.
Maybe an expert can look into this. It would make a great library even better.