From c4eb14f5cd1cf499b7d5eaf944b6c200c0d6cd10 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Tim=20D=C3=BCsterhus?= <duesterhus@woltlab.com>
Date: Fri, 29 Mar 2019 17:22:23 +0100
Subject: [PATCH] Preserve file type if image contains transparent pixels

---
 wcfsetup/install/files/js/WCF.Attachment.js   |  7 +++--
 .../WoltLabSuite/Core/{ => Image}/ExifUtil.js |  2 +-
 .../js/WoltLabSuite/Core/Image/ImageUtil.js   | 29 +++++++++++++++++++
 .../{ImageResizer.js => Image/Resizer.js}     |  7 +++--
 wcfsetup/install/lang/de.xml                  |  2 +-
 wcfsetup/install/lang/en.xml                  |  2 +-
 6 files changed, 40 insertions(+), 9 deletions(-)
 rename wcfsetup/install/files/js/WoltLabSuite/Core/{ => Image}/ExifUtil.js (99%)
 create mode 100644 wcfsetup/install/files/js/WoltLabSuite/Core/Image/ImageUtil.js
 rename wcfsetup/install/files/js/WoltLabSuite/Core/{ImageResizer.js => Image/Resizer.js} (97%)

diff --git a/wcfsetup/install/files/js/WCF.Attachment.js b/wcfsetup/install/files/js/WCF.Attachment.js
index 8abb95b879..34cf0c4720 100644
--- a/wcfsetup/install/files/js/WCF.Attachment.js
+++ b/wcfsetup/install/files/js/WCF.Attachment.js
@@ -296,9 +296,10 @@ if (COMPILER_TARGET_DEFAULT) {
 			
 			require([
 				'WoltLabSuite/Core/FileUtil',
-				'WoltLabSuite/Core/ImageResizer',
+				'WoltLabSuite/Core/Image/ImageUtil',
+				'WoltLabSuite/Core/Image/Resizer',
 				'WoltLabSuite/Core/Ajax/Status'
-			], (function (FileUtil, ImageResizer, AjaxStatus) {
+			], (function (FileUtil, ImageUtil, ImageResizer, AjaxStatus) {
 				AjaxStatus.show();
 				
 				var files = [];
@@ -360,7 +361,7 @@ if (COMPILER_TARGET_DEFAULT) {
 											
 											var fileType = this._options.autoScale.fileType;
 											
-											if (this._options.autoScale.fileType === 'keep') {
+											if (this._options.autoScale.fileType === 'keep' || ImageUtil.containsTransparentPixels(resizedImage)) {
 												fileType = file.type;
 											}
 											
diff --git a/wcfsetup/install/files/js/WoltLabSuite/Core/ExifUtil.js b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/ExifUtil.js
similarity index 99%
rename from wcfsetup/install/files/js/WoltLabSuite/Core/ExifUtil.js
rename to wcfsetup/install/files/js/WoltLabSuite/Core/Image/ExifUtil.js
index 8db5931941..618446cc7d 100644
--- a/wcfsetup/install/files/js/WoltLabSuite/Core/ExifUtil.js
+++ b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/ExifUtil.js
@@ -4,7 +4,7 @@
  * @author	Maximilian Mader
  * @copyright	2001-2018 WoltLab GmbH
  * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @module	WoltLabSuite/Core/ExifUtil
+ * @module	WoltLabSuite/Core/Image/ExifUtil
  */
 define([], function() {
 	"use strict";
diff --git a/wcfsetup/install/files/js/WoltLabSuite/Core/Image/ImageUtil.js b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/ImageUtil.js
new file mode 100644
index 0000000000..cd558c4be5
--- /dev/null
+++ b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/ImageUtil.js
@@ -0,0 +1,29 @@
+/**
+ * Provides helper functions for Image metadata handling.
+ *
+ * @author	Tim Duesterhus
+ * @copyright	2001-2019 WoltLab GmbH
+ * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @module	WoltLabSuite/Core/Image/ImageUtil
+ */
+define([], function() {
+	"use strict";
+	
+	return {
+		/**
+		 * Returns whether the given canvas contains transparent pixels.
+		 *
+		 * @param       image   {Canvas}  Canvas to check
+		 * @returns             {bool}
+		 */
+		containsTransparentPixels: function (canvas) {
+			var imageData = canvas.getContext('2d').getImageData(0, 0, canvas.width, canvas.height);
+			
+			for (var i = 3, max = imageData.data.length; i < max; i += 4) {
+				if (imageData.data[i] !== 255) return true;
+			}
+			
+			return false;
+		}
+	};
+});
diff --git a/wcfsetup/install/files/js/WoltLabSuite/Core/ImageResizer.js b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/Resizer.js
similarity index 97%
rename from wcfsetup/install/files/js/WoltLabSuite/Core/ImageResizer.js
rename to wcfsetup/install/files/js/WoltLabSuite/Core/Image/Resizer.js
index 3765407e3f..f427f6159e 100644
--- a/wcfsetup/install/files/js/WoltLabSuite/Core/ImageResizer.js
+++ b/wcfsetup/install/files/js/WoltLabSuite/Core/Image/Resizer.js
@@ -4,11 +4,11 @@
  * @author	Maximilian Mader
  * @copyright	2001-2018 WoltLab GmbH
  * @license	GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @module	WoltLabSuite/Core/ImageResizer
+ * @module	WoltLabSuite/Core/Image/Resizer
  */
 define([
 	'WoltLabSuite/Core/FileUtil',
-	'WoltLabSuite/Core/ExifUtil',
+	'WoltLabSuite/Core/Image/ExifUtil',
 	'Pica'
 ], function(FileUtil, ExifUtil, Pica) {
 	"use strict";
@@ -194,7 +194,8 @@ define([
 			
 			var options = {
 				quality: resizeQuality,
-				cancelToken: cancelPromise
+				cancelToken: cancelPromise,
+				alpha: true
 			};
 			
 			return pica.resize(image, canvas, options);
diff --git a/wcfsetup/install/lang/de.xml b/wcfsetup/install/lang/de.xml
index a1421fcdc0..30d47dd5e7 100644
--- a/wcfsetup/install/lang/de.xml
+++ b/wcfsetup/install/lang/de.xml
@@ -1392,7 +1392,7 @@ Das Fehlerprotokoll enthält {$data[count]} neue Einträge. Die ersten drei, in
 		<item name="wcf.acp.option.attachment_image_autoscale_quality"><![CDATA[Qualitätsstufe]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_quality.description"><![CDATA[Bestimmt die Qualität des skalierten Bildes.]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_file_type"><![CDATA[Dateityp]]></item>
-		<item name="wcf.acp.option.attachment_image_autoscale_file_type.jpeg"><![CDATA[JPEG (verlustbehaftet, keine Transparenz, erzeugt in der Regel kleine Dateien)]]></item>
+		<item name="wcf.acp.option.attachment_image_autoscale_file_type.jpeg"><![CDATA[JPEG (verlustbehaftet, erzeugt in der Regel kleine Dateien)]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_file_type.keep"><![CDATA[Dateityp beibehalten]]></item>
 		<item name="wcf.acp.option.module_attachment"><![CDATA[Dateianhänge]]></item>
 		<item name="wcf.acp.option.module_smiley"><![CDATA[Smileys]]></item>
diff --git a/wcfsetup/install/lang/en.xml b/wcfsetup/install/lang/en.xml
index 0ba9e5857a..3f3eb676e6 100644
--- a/wcfsetup/install/lang/en.xml
+++ b/wcfsetup/install/lang/en.xml
@@ -1369,7 +1369,7 @@ This protocol file contains {$data[count]} new entries. The first three error me
 		<item name="wcf.acp.option.attachment_image_autoscale_quality"><![CDATA[Quality]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_quality.description"><![CDATA[Defines the quality of the scaled image.]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_file_type"><![CDATA[File type]]></item>
-		<item name="wcf.acp.option.attachment_image_autoscale_file_type.jpeg"><![CDATA[JPEG (lossy, does not support transparency, usually the generated files are small)]]></item>
+		<item name="wcf.acp.option.attachment_image_autoscale_file_type.jpeg"><![CDATA[JPEG (lossy, usually the generated files are small)]]></item>
 		<item name="wcf.acp.option.attachment_image_autoscale_file_type.keep"><![CDATA[Keep the file type]]></item>
 		<item name="wcf.acp.option.module_attachment"><![CDATA[Attachments]]></item>
 		<item name="wcf.acp.option.module_smiley"><![CDATA[Smilies]]></item>
-- 
2.20.1