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<title>[56271] trunk: Media: Adjust PDF upload handling to remove non-opaque alpha channels from previews.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/56271">56271</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/56271","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>antpb</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2023-07-19 22:33:47 +0000 (Wed, 19 Jul 2023)</dd>
</dl>
<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Media: Adjust PDF upload handling to remove non-opaque alpha channels from previews.
Previously, Imagick uploads of PDF files with non-opaque alpha channels would result in a black background replacing alpha in the generated thumbnail. This patch adds a `remove_pdf_alpha_channel()` function in the Imagick classes to use a white background instead.
Props gitlost, joemcgill, joedolson, launchinteractive, emirpprime, mwtsn, ceer, maysi, madejackson, 6adminit, costdev, oglekler.
Fixes <a href="https://core.trac.wordpress.org/ticket/39216">#39216</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludesclasswpimageeditorimagickphp">trunk/src/wp-includes/class-wp-image-editor-imagick.php</a></li>
<li><a href="#trunktestsphpunittestsimageeditorImagickphp">trunk/tests/phpunit/tests/image/editorImagick.php</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunktestsphpunitdataimagestestalphapdf">trunk/tests/phpunit/data/images/test-alpha.pdf</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludesclasswpimageeditorimagickphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/class-wp-image-editor-imagick.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/class-wp-image-editor-imagick.php 2023-07-19 11:31:15 UTC (rev 56270)
+++ trunk/src/wp-includes/class-wp-image-editor-imagick.php 2023-07-19 22:33:47 UTC (rev 56271)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -168,6 +168,10 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $this->image->setIteratorIndex( 0 );
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ if ( 'pdf' === $file_extension ) {
+ $this->remove_pdf_alpha_channel();
+ }
+
</ins><span class="cx" style="display: block; padding: 0 10px"> $this->mime_type = $this->get_mime_type( $this->image->getImageFormat() );
</span><span class="cx" style="display: block; padding: 0 10px"> } catch ( Exception $e ) {
</span><span class="cx" style="display: block; padding: 0 10px"> return new WP_Error( 'invalid_image', $e->getMessage(), $this->file );
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -752,6 +756,24 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * Removes PDF alpha after it's been read.
+ *
+ * @since 6.4.0
+ */
+ protected function remove_pdf_alpha_channel() {
+ $version = Imagick::getVersion();
+ // Remove alpha channel if possible to avoid black backgrounds for Ghostscript >= 9.14. RemoveAlphaChannel added in ImageMagick 6.7.5.
+ if ( $version['versionNumber'] >= 0x675 ) {
+ try {
+ // Imagick::ALPHACHANNEL_REMOVE mapped to RemoveAlphaChannel in PHP imagick 3.2.0b2.
+ $this->image->setImageAlphaChannel( defined( 'Imagick::ALPHACHANNEL_REMOVE' ) ? Imagick::ALPHACHANNEL_REMOVE : 12 );
+ } catch ( Exception $e ) {
+ return new WP_Error( 'pdf_alpha_process_failed', $e->getMessage() );
+ }
+ }
+ }
+
+ /**
</ins><span class="cx" style="display: block; padding: 0 10px"> * @since 3.5.0
</span><span class="cx" style="display: block; padding: 0 10px"> * @since 6.0.0 The `$filesize` value was added to the returned array.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span></span></pre></div>
<a id="trunktestsphpunitdataimagestestalphapdf"></a>
<div class="binary"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Added: trunk/tests/phpunit/data/images/test-alpha.pdf</h4>
<pre class="diff"><span>
<span class="cx">(Binary files differ)
</span></span></pre></div>
<span class="cx" style="display: block; padding: 0 10px">Index: trunk/tests/phpunit/data/images/test-alpha.pdf
</span><span class="cx" style="display: block; padding: 0 10px">===================================================================
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">--- trunk/tests/phpunit/data/images/test-alpha.pdf 2023-07-19 11:31:15 UTC (rev 56270)
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+++ trunk/tests/phpunit/data/images/test-alpha.pdf 2023-07-19 22:33:47 UTC (rev 56271)
</ins><span class="cx" style="display: block; padding: 0 10px">Property changes on: trunk/tests/phpunit/data/images/test-alpha.pdf
</span><span class="cx" style="display: block; padding: 0 10px">___________________________________________________________________
</span><a id="svnmimetype"></a>
<div class="addfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Added: svn:mime-type</h4></div>
<ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+application/octet-stream
</ins><span class="cx" style="display: block; padding: 0 10px">\ No newline at end of property
</span><a id="trunktestsphpunittestsimageeditorImagickphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/image/editorImagick.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/image/editorImagick.php 2023-07-19 11:31:15 UTC (rev 56270)
+++ trunk/tests/phpunit/tests/image/editorImagick.php 2023-07-19 22:33:47 UTC (rev 56271)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -641,4 +641,54 @@
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> $this->assertNotWPError( $saved );
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+ /**
+ * Tests that the alpha channel of PDFs is removed from PDF previews.
+ *
+ * Only affects systems with Ghostscript version >= 9.14.
+ *
+ * @ticket 39216
+ *
+ * @covers WP_Image_Editor_Imagick::remove_pdf_alpha_channel
+ */
+ public function test_remove_pdf_alpha_channel_should_remove_the_alpha_channel_in_preview() {
+ if ( ! wp_image_editor_supports( array( 'mime_type' => 'application/pdf' ) ) ) {
+ $this->markTestSkipped( 'Rendering PDFs is not supported on this system.' );
+ }
+
+ $test_file = DIR_TESTDATA . '/images/test-alpha.pdf';
+ $attachment_id = $this->factory->attachment->create_upload_object( $test_file );
+ $this->assertNotEmpty( $attachment_id, 'The attachment was not created before testing.' );
+
+ $attached_file = get_attached_file( $attachment_id );
+ $this->assertNotEmpty( $attached_file, 'The attached file was not returned.' );
+
+ $rgb = array(
+ 'r' => true,
+ 'g' => true,
+ 'b' => true,
+ );
+
+ // White.
+ $expected = array(
+ 'r' => 1,
+ 'g' => 1,
+ 'b' => 1,
+ );
+
+ $check = image_get_intermediate_size( $attachment_id, 'full' );
+ $this->assertIsArray( $check, 'The intermediate size could not be retrieved.' );
+ $this->assertArrayHasKey( 'file', $check, 'The intermediate size file was not found.' );
+
+ $check_file = path_join( dirname( $attached_file ), $check['file'] );
+ $imagick = new Imagick( $check_file );
+ $output = array_map(
+ static function( $value ) {
+ return (int) round( $value );
+ },
+ array_intersect_key( $imagick->getImagePixelColor( 100, 100 )->getColor( true /* normalized */ ), $rgb )
+ );
+ $imagick->destroy();
+ $this->assertSame( $expected, $output, 'The image color of the generated thumb does not match expected opaque background.' ); // Allow for floating point equivalence.
+ }
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span></span></pre>
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