From d15d0bf221893df55333cbee96c2bd421f13fc8a Mon Sep 17 00:00:00 2001
From: Nora Trapp <nora@signal.org>
Date: Fri, 23 Jul 2021 16:21:53 -0700
Subject: [PATCH] Preserve image orientation when downsampling is not required

---
 .../attachments/SignalAttachment.swift        | 21 +++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/SignalMessaging/attachments/SignalAttachment.swift b/SignalMessaging/attachments/SignalAttachment.swift
index 1c1d64a66c..a86e4c6354 100644
--- a/SignalMessaging/attachments/SignalAttachment.swift
+++ b/SignalMessaging/attachments/SignalAttachment.swift
@@ -866,6 +866,7 @@ public class SignalAttachment: NSObject {
 
             let maxSize = imageUploadQuality.maxEdgeSize
             let pixelSize = dataSource.imageMetadata.pixelSize
+            var imageProperties = [CFString: Any]()
 
             let cgImage: CGImage
             if pixelSize.width > maxSize || pixelSize.height > maxSize {
@@ -879,6 +880,20 @@ public class SignalAttachment: NSObject {
                     return .error(error: .couldNotParseImage)
                 }
 
+                guard let originalImageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, [
+                    kCGImageSourceShouldCache: false
+                ] as CFDictionary) as? [CFString: Any] else {
+                    return .error(error: .couldNotParseImage)
+                }
+
+                // Preserve any orientation properties in the final output image.
+                if let tiffOrientation = originalImageProperties[kCGImagePropertyTIFFOrientation] {
+                    imageProperties[kCGImagePropertyTIFFOrientation] = tiffOrientation
+                }
+                if let iptcOrientation = originalImageProperties[kCGImagePropertyIPTCImageOrientation] {
+                    imageProperties[kCGImagePropertyIPTCImageOrientation] = iptcOrientation
+                }
+
                 guard let image = CGImageSourceCreateImageAtIndex(imageSource, 0, [
                     kCGImageSourceShouldCacheImmediately: true
                 ] as CFDictionary) else {
@@ -894,7 +909,6 @@ public class SignalAttachment: NSObject {
             let dataFileExtension: String
             let dataUTI: CFString
             let dataMIMEType: String
-            let imageProperties: CFDictionary?
 
             // We convert everything that's not sticker-like to jpg, because
             // often images with alpha channels don't actually have any
@@ -905,12 +919,11 @@ public class SignalAttachment: NSObject {
                 dataFileExtension = "png"
                 dataUTI = kUTTypePNG
                 dataMIMEType = OWSMimeTypeImagePng
-                imageProperties = nil
             } else {
                 dataFileExtension = "jpg"
                 dataUTI = kUTTypeJPEG
                 dataMIMEType = OWSMimeTypeImageJpeg
-                imageProperties = [kCGImageDestinationLossyCompressionQuality: compressionQuality(for: pixelSize)] as CFDictionary
+                imageProperties[kCGImageDestinationLossyCompressionQuality] = compressionQuality(for: pixelSize)
             }
 
             let tempFileUrl = OWSFileSystem.temporaryFileUrl(fileExtension: dataFileExtension)
@@ -918,7 +931,7 @@ public class SignalAttachment: NSObject {
                 owsFailDebug("Failed to create CGImageDestination for attachment")
                 return .error(error: .couldNotConvertImage)
             }
-            CGImageDestinationAddImage(destination, cgImage, imageProperties)
+            CGImageDestinationAddImage(destination, cgImage, imageProperties as CFDictionary)
             guard CGImageDestinationFinalize(destination) else {
                 owsFailDebug("Failed to write downsampled attachment to disk")
                 return .error(error: .couldNotConvertImage)