Mpdf Large Images

See PR PHPOffice#2879 Issue PHPOffice#2876.

Author: oleibman

src/PhpWord/Writer/PDF/MPDF.php

@@ -88,8 +88,23 @@ public function save(string $filename): void
             $pdf->WriteHTML(substr($html, 0, $bodyLocation));
             $html = substr($html, $bodyLocation);
         }
-        foreach (explode("\n", $html) as $line) {
-            $pdf->WriteHTML("$line\n");
+        $pcreBacktrackLimitString = ini_get('pcre.backtrack_limit');
+        $pcreBacktrackLimit = (int) $pcreBacktrackLimitString;
+        $origLimit = $pcreBacktrackLimit;
+
+        try {
+            foreach (explode("\n", $html) as $line) {
+                $lineLen = strlen($line);
+                if ($lineLen > $pcreBacktrackLimit) {
+                    $pcreBacktrackLimit = $lineLen + 1;
+                    ini_set('pcre.backtrack_limit', (string) $pcreBacktrackLimit);
+                }
+                $pdf->WriteHTML("$line\n");
+            }
+        } finally {
+            if ($pcreBacktrackLimit !== $origLimit) {
+                ini_set('pcre.backtrack_limit', $pcreBacktrackLimitString);
+            }
         }
 
         //  Write to file

tests/PhpWordTests/Writer/PDF/MpdfLargeImageTest.php

@@ -0,0 +1,106 @@
+<?php
+
+/**
+ * This file is part of PHPWord - A pure PHP library for reading and writing
+ * word processing documents.
+ *
+ * PHPWord is free software distributed under the terms of the GNU Lesser
+ * General Public License version 3 as published by the Free Software Foundation.
+ *
+ * For the full copyright and license information, please read the LICENSE
+ * file that was distributed with this source code. For the full list of
+ * contributors, visit https://github.com/PHPOffice/PHPWord/contributors.
+ *
+ * @see        https://github.com/PHPOffice/PHPWord
+ *
+ * @license    http://www.gnu.org/licenses/lgpl.txt LGPL version 3
+ */
+
+namespace PhpOffice\PhpWordTests\Writer\PDF;
+
+use PhpOffice\PhpWord\PhpWord;
+use PhpOffice\PhpWord\Writer\PDF\MPDF;
+
+/**
+ * Test class for PhpOffice\PhpWord\Writer\PDF\MPDF.
+ *
+ * @runTestsInSeparateProcesses
+ */
+class MpdfLargeImageTest extends \PHPUnit\Framework\TestCase
+{
+    /** @var string */
+    private $jpegName = '';
+
+    /** @var string */
+    private $pdfName = '';
+
+    protected function tearDown(): void
+    {
+        // Nothing sensible to do if unlink fails.
+        if ($this->jpegName !== '') {
+            @unlink($this->jpegName);
+        }
+        if ($this->pdfName !== '') {
+            @unlink($this->pdfName);
+        }
+    }
+
+    /**
+     * Test that a large embedded image does not trigger the pcre.backtrack_limit error (issue #2876).
+     *
+     * PHPWord embeds images as base64 data URIs on a single HTML line. When the image is large
+     * the line exceeds pcre.backtrack_limit and Mpdf refuses the WriteHTML call. The fix must
+     * handle this gracefully without requiring the caller to raise pcre.backtrack_limit.
+     */
+    public function testLargeImageDoesNotExceedBacktrackLimit(): void
+    {
+        // Generate a random-noise JPEG (~700-900 KB) that resists JPEG compression.
+        // The resulting base64 data URI will be a single HTML line > 900 KB,
+        // which exceeds the default pcre.backtrack_limit of 1 000 000.
+        $size1 = 1600;
+        $size2 = 1200;
+        $img = imagecreatetruecolor($size1, $size2);
+        if ($img === false) {
+            self::fail('imagecreatetruecolor() failed.');
+        }
+        for ($y = 0; $y < $size2; ++$y) {
+            for ($x = 0; $x < $size1; ++$x) {
+                imagesetpixel($img, $x, $y, (int) imagecolorallocate($img, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255)));
+            }
+        }
+        ob_start();
+        self::assertTrue(imagejpeg($img, null, 95));
+        $imageData = ob_get_clean();
+        imagedestroy($img);
+
+        $tmpImage = $this->jpegName = tempnam(sys_get_temp_dir(), 'tmp_');
+        file_put_contents($tmpImage, $imageData);
+
+        $pcreBacktrackLimitOld = ini_get('pcre.backtrack_limit');
+        $phpWord = new PhpWord();
+        $section = $phpWord->addSection();
+        $section->addText('Large-image PDF — issue #2876 regression test');
+        $section->addImage($tmpImage, ['width' => 400, 'height' => 267]);
+
+        $writer = new MPDF($phpWord);
+        $file = $this->pdfName = tempnam(sys_get_temp_dir(), 'tmp_');
+        $writer->save($file);
+
+        $pcreBacktrackLimitNew = ini_get('pcre.backtrack_limit');
+        self::assertSame($pcreBacktrackLimitOld, $pcreBacktrackLimitNew);
+        self::assertFileExists($file);
+        self::assertGreaterThan(0, filesize($file));
+
+        $longLine = false;
+        $maxLen = (int) $pcreBacktrackLimitOld;
+        $html = $writer->getContent();
+        foreach (explode("\n", $html) as $line) {
+            if (strlen($line) > $maxLen) {
+                $longLine = true;
+
+                break;
+            }
+        }
+        self::assertTrue($longLine);
+    }
+}