From 505fe2f0b87bba956d399f657f85a7073c978289 Mon Sep 17 00:00:00 2001
From: Mike Schroder <mikeschroder@git.wordpress.org>
Date: Fri, 16 Oct 2020 10:46:58 +0000
Subject: [PATCH] Media: Work around `use-cropbox` bug in Ghostscript 8.70

Wraps `Imagick::readImage()` for PDFs with exception handling, trying again without `use-cropbox` if this fails.

Introduces `WP_Image_Editor_Imagick::pdf_load_source()`.

Works around a known issue in Ghostscript 8.70 (fixed in 8.71) that results in a stack underflow.
While it only affects this version, it remains a common version found on hosts, and prevented some PDF thumbnails from being generated.

See this Ghostscript bug for more details: https://bugs.ghostscript.com/show_bug.cgi?id=690676

Props azaozz, joseaneto, cranewest, dantahoua, n5hzr, mikeschroder.
Fixes #48853.

git-svn-id: https://develop.svn.wordpress.org/trunk@49174 602fd350-edb4-49c9-b593-d223f7449a82
---
 .../class-wp-image-editor-imagick.php         | 53 +++++++++++++++----
 1 file changed, 43 insertions(+), 10 deletions(-)

diff --git a/src/wp-includes/class-wp-image-editor-imagick.php b/src/wp-includes/class-wp-image-editor-imagick.php
index dbdf1607cd..0d2aa05ac7 100644
--- a/src/wp-includes/class-wp-image-editor-imagick.php
+++ b/src/wp-includes/class-wp-image-editor-imagick.php
@@ -140,15 +140,16 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 		try {
 			$this->image    = new Imagick();
 			$file_extension = strtolower( pathinfo( $this->file, PATHINFO_EXTENSION ) );
-			$filename       = $this->file;
 
 			if ( 'pdf' === $file_extension ) {
-				$filename = $this->pdf_setup();
-			}
+				$pdf_loaded = $this->pdf_load_source();
 
-			// Reading image after Imagick instantiation because `setResolution`
-			// only applies correctly before the image is read.
-			$this->image->readImage( $filename );
+				if ( is_wp_error( $pdf_loaded ) ) {
+					return $pdf_loaded;
+				}
+			} else {
+				$this->image->readImage( $this->file );
+			}
 
 			if ( ! $this->image->valid() ) {
 				return new WP_Error( 'invalid_image', __( 'File is not an image.' ), $this->file );
@@ -165,6 +166,7 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 		}
 
 		$updated_size = $this->update_size();
+
 		if ( is_wp_error( $updated_size ) ) {
 			return $updated_size;
 		}
@@ -795,10 +797,6 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 			// We want the thumbnail to be readable, so increase the rendering DPI.
 			$this->image->setResolution( 128, 128 );
 
-			// When generating thumbnails from cropped PDF pages, Imagemagick uses the uncropped
-			// area (resulting in unnecessary whitespace) unless the following option is set.
-			$this->image->setOption( 'pdf:use-cropbox', true );
-
 			// Only load the first page.
 			return $this->file . '[0]';
 		} catch ( Exception $e ) {
@@ -806,4 +804,39 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 		}
 	}
 
+	/**
+	 * Load the image produced by Ghostscript.
+	 *
+	 * Includes a workaround for a bug in Ghostscript 8.70 that prevents processing of some PDF files
+	 * when `use-cropbox` is set.
+	 *
+	 * @since 5.6
+	 *
+	 * @return true|WP_error
+	 */
+	protected function pdf_load_source() {
+		$filename = $this->pdf_setup();
+
+		if ( is_wp_error( $filename ) ) {
+			return $filename;
+		}
+
+		try {
+			// When generating thumbnails from cropped PDF pages, Imagemagick uses the uncropped
+			// area (resulting in unnecessary whitespace) unless the following option is set.
+			$this->image->setOption( 'pdf:use-cropbox', true );
+
+			// Reading image after Imagick instantiation because `setResolution`
+			// only applies correctly before the image is read.
+			$this->image->readImage( $filename );
+		} catch ( Exception $e ) {
+			// Attempt to run `gs` without the `use-cropbox` option. See #48853.
+			$this->image->setOption( 'pdf:use-cropbox', false );
+
+			$this->image->readImage( $filename );
+		}
+
+		return true;
+	}
+
 }