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Tesseract OCR in PHP, tested on 55 scans

3.2x

less CPU: one call, many images

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The code, run on 55 scans

The package runs the tesseract command, so install that first: brew install tesseract on a Mac, apt-get install tesseract-ocr on Debian or Ubuntu. 

composer require thiagoalessio/tesseract_ocr:2.13.0
<?php
require __DIR__ . '/vendor/autoload.php';

use thiagoalessio\TesseractOCR\TesseractOCR;

echo (new TesseractOCR('scan.jpg'))->dpi(300)->run();

55 of 55 scans, the command's text

13,858 of 14,693 words found, both

Works in the terminal, fails on the web

The same code under php-fpm, from Homebrew's PHP:

Error! The command "tesseract" was not found.

Make sure you have Tesseract OCR installed on your system:
https://github.com/tesseract-ocr/tesseract

The current $PATH is

The empty $PATH is the clue. php-fpm clears the environment of its workers by default, so PHP cannot see /opt/homebrew/bin. Either fix worked: 

echo (new TesseractOCR('scan.jpg'))
    ->executable('/opt/homebrew/bin/tesseract')
    ->dpi(300)->run();

Or add this line to the pool's www.conf and restart php-fpm:

env[PATH] = /opt/homebrew/bin:/usr/bin:/bin

Set the dpi to match the command

My scans have no dpi in the file, so without ->dpi(300) Tesseract guesses it. The page mode needs nothing: the default is psm 3, like the command's.

40 of 55 scans, the command's text without it

13,855 words found, 3 fewer

Same text, more CPU on small images

CPU seconds, Tesseract 5.5.4
Job shell_exec Wrapper
55 full pages 143.0 s 144.6 s
259 line images 45.4 s 54.5 s

Before each image, the wrapper starts tesseract once more to read its version. A big page hides that. A small image does not.

2 tesseract starts per image

4 with imageData() and withoutTempFiles()

Many small images: one call

Tesseract reads a text file of image paths in one run. The model loads once: 

$list = tempnam(sys_get_temp_dir(), 'list');
file_put_contents($list, implode("\n", $files) . "\n");
$text = (new TesseractOCR($list))
    ->dpi(300)->psm(7)
    ->config('page_separator', '[page]')
    ->run();
unlink($list);
$texts = explode('[page]', $text);
if (count($texts) !== count($files)) {
    throw new RuntimeException('Tesseract stopped early.');
}

17.1 s for 259 lines, not 54.5 s

All 259 lines, the command's text

Keep the count check. A file Tesseract cannot read stops the run, and the wrapper returns the text so far with no error.

The wrapper trims form feeds, the default separator, from both ends. With a blank last image, 3 images came back as 2 parts.

PDFs: make gray images first

Two lines of the wrapper's PDF error:

Error! The command did not produce any output.
Error in pixReadStream: Pdf reading is not supported

Make an image of each page at 300 dpi first:

$dir = sys_get_temp_dir() . '/pdf-' . uniqid();
mkdir($dir);
exec('pdftoppm -r 300 -gray ' . escapeshellarg('scan.pdf') . ' ' . escapeshellarg("$dir/page"));
$text = '';
foreach (glob("$dir/page-*") as $img) {
    $text .= (new TesseractOCR($img))->dpi(300)->run() . "\n";
    unlink($img);
}
rmdir($dir);
10 pages, 1,955 true words
Pages to images CPU a page Words
pdftoppm -png 13.1 s 1,879
pdftoppm -gray 2.4 s 1,882
pdfimages -all 3.0 s 1,878

PNG writing took most of the PNG run. -gray writes plain PGM files.

Debian in Docker: same text as apt's command

FROM php:8.4-cli
RUN apt-get update \
 && apt-get install -y --no-install-recommends tesseract-ocr unzip \
 && rm -rf /var/lib/apt/lists/*
COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
WORKDIR /app
RUN composer require thiagoalessio/tesseract_ocr:2.13.0
COPY index.php scan.jpg ./
CMD ["php", "index.php"]

With the code above as index.php, it matched apt's tesseract (5.5.0) on 5 of 5 scans.

How I tested it
  • Pages: 55 proofread Wikisource scans from 11 printed books, JPEG, 1,920 pixels wide, no dpi in the file. The same set as Tesseract in C#.
  • Score: true words found in order, with the scorer of the tessdata test.
  • Apple Silicon Mac, PHP 8.5.12 and Composer 2.11.1 from Homebrew, the wrapper 2.13.0, Tesseract 5.5.4, tessdata_fast English.
  • CPU time of the whole process tree, PHP start included, on the Mac's efficiency cores. A second round of the line jobs gave 52.8 s, 60.9 s and 18.0 s.
  • Web: Homebrew's php-fpm 8.5.12 with the default clear_env, one scan, through a FastCGI client.
  • PDF: the first 10 scans in one PDF, JPEG bytes kept, page size for 300 dpi. pdftoppm 26.03.0.
What I did not test
  • Windows, Intel Macs, x86-64 Linux, and php-fpm on Linux.
  • Apache with mod_php, Laravel Herd and Valet.
  • Imagick for PDFs, and other wrapper versions.
  • Other languages, tessdata_best, and photos.
Sources

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Questions people ask

Does the wrapper give the same text as the command?

Yes, on 55 of 55 scans, with the same Tesseract, the same model, psm 3 and 300 dpi on both. It runs the command and trims the ends.

Why does it work in the terminal but not in the browser?

php-fpm clears the environment of its workers by default, so PHP has no $PATH and cannot see Homebrew's tesseract. Pass the full path with executable(), or set env[PATH] in the pool.

Can it read a PDF?

No. Tesseract reads images only. Make an image of each page first, for example with pdftoppm -r 300 -gray, then read each image.

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