Image just some color converted into black and white

[Stéphane Brunner]

Hello,

When I run the command:
tesseract image-1.png output -l fra pdf 

With an image that contains e.g. a black and white test and just a blue signature, in the generated PDF the signature is in gray!

More information about the image

file image-1.png

image-1.png: PNG image data, 1989 x 2858, 4-bit colormap, non-interlaced

Is there an option in Tesseract to avoid this conversion?

Thanks in advance
Stéphane

[Zdenko Podobny]

Which version of tesseract you use? Can you provide test image?

Zdenko

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[Stéphane Brunner]

Hello,

tesseract --version
tesseract 5.3.4
 leptonica-1.82.0
  libgif 5.2.1 : libjpeg 8d (libjpeg-turbo 2.1.5) : libpng 1.6.43 : libtiff 4.5.1 : zlib 1.3 : libwebp 1.3.2 : libopenjp2 2.5.0
 Found AVX512BW
 Found AVX512F
 Found AVX512VNNI
 Found AVX2
 Found AVX
 Found FMA
 Found SSE4.1
 Found OpenMP 201511
 Found libarchive 3.7.2 zlib/1.3 liblzma/5.4.5 bz2lib/1.0.8 liblz4/1.9.4 libzstd/1.5.5
 Found libcurl/8.5.0 OpenSSL/3.0.13 zlib/1.3 brotli/1.1.0 zstd/1.5.5 libidn2/2.3.7 libpsl/0.21.2 (+libidn2/2.3.7) libssh/0.10.6/openssl/zlib nghttp2/1.59.0 librtmp/2.3 OpenLDAP/2.6.7

> Can you provide test image?

No because she contains personal data, but I build an image that generates the same issue

Note the with Gimp I create a PNG image with 256 colors that doesn't have the issue then I optimize it with pngquant:
pngquant --force --speed=1 --strip --quality=0-31 - < image-gimp.png > image.png

And the generated image has the issue!

Then if I can do something on my image as a workaround that didn't deoptimize the image, it will be fine :-)

Does the newer version of Tesseract resolve this issue?

Thanks in advance

Stéphane

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[Zdenko Podobny]

Hello,

You are using old version of tesseract - please update to current version 5.5.1

Zdenko

so 22. 11. 2025 o 18:23 Stéphane Brunner <stephane...@gmail.com> napísal(a):

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