Use TryGetExifOrientation

Author: JimBobSquarePants

src/ImageSharp.Web/FormattedImage.cs

@@ -119,39 +119,38 @@ public static async Task<FormattedImage> LoadAsync(Configuration configuration,
         public Task SaveAsync(Stream destination) => this.Image.SaveAsync(destination, this.encoder);
 
         /// <summary>
-        /// Returns a value indicating whether the source image contains EXIF metadata for <see cref="ExifTag.Orientation"/>
-        /// indicating that the image is rotated (not flipped).
+        /// Gets the EXIF orientation metata for the <see cref="FormattedImage"/>.
         /// </summary>
-        /// <param name="orientation">The decoded orientation. Use <see cref="ExifOrientationMode"/> for comparison.</param>
-        /// <returns>The <see cref="bool"/> indicating whether the image contains EXIF metadata indicating that the image is rotated.</returns>
-        public bool IsExifRotated(out ushort orientation)
+        /// <param name="value">
+        /// When this method returns, contains the value parsed from decoded EXIF metadata; otherwise,
+        /// the default value for the type of the <paramref name="value"/> parameter.
+        /// This parameter is passed uninitialized. Use <see cref="ExifOrientationMode"/> for comparison.
+        /// </param>
+        /// <returns>
+        /// <see langword="true"/> if the <see cref="FormattedImage"/> contains EXIF orientation metadata
+        /// for <see cref="ExifTag.Orientation"/>; otherwise, <see langword="false"/>.
+        /// </returns>
+        public bool TryGetExifOrientation(out ushort value)
         {
-            orientation = ExifOrientationMode.Unknown;
+            value = ExifOrientationMode.Unknown;
             if (this.Image.Metadata.ExifProfile != null)
             {
-                IExifValue<ushort> value = this.Image.Metadata.ExifProfile.GetValue(ExifTag.Orientation);
-                if (value is null)
+                IExifValue<ushort> orientation = this.Image.Metadata.ExifProfile.GetValue(ExifTag.Orientation);
+                if (orientation is null)
                 {
                     return false;
                 }
 
-                if (value.DataType == ExifDataType.Short)
+                if (orientation.DataType == ExifDataType.Short)
                 {
-                    orientation = value.Value;
+                    value = orientation.Value;
                 }
                 else
                 {
-                    orientation = Convert.ToUInt16(value.Value);
+                    value = Convert.ToUInt16(orientation.Value);
                 }
 
-                return orientation switch
-                {
-                    ExifOrientationMode.LeftTop
-                    or ExifOrientationMode.RightTop
-                    or ExifOrientationMode.RightBottom
-                    or ExifOrientationMode.LeftBottom => true,
-                    _ => false,
-                };
+                return true;
             }
 
             return false;

src/ImageSharp.Web/Processors/ResizeWebProcessor.cs

@@ -112,9 +112,9 @@ internal static ResizeOptions GetResizeOptions(
                 return null;
             }
 
-            bool rotated = ShouldHandleExifRotation(image, commands, parser, culture, out ushort orientation);
+            ushort orientation = GetExifOrientation(image, commands, parser, culture);
 
-            Size size = ParseSize(rotated, commands, parser, culture);
+            Size size = ParseSize(orientation, commands, parser, culture);
 
             if (size.Width <= 0 && size.Height <= 0)
             {
@@ -137,15 +137,18 @@ internal static ResizeOptions GetResizeOptions(
         }
 
         private static Size ParseSize(
-            bool rotated,
+            ushort orientation,
             CommandCollection commands,
             CommandParser parser,
             CultureInfo culture)
         {
             // The command parser will reject negative numbers as it clamps values to ranges.
             int width = (int)parser.ParseValue<uint>(commands.GetValueOrDefault(Width), culture);
             int height = (int)parser.ParseValue<uint>(commands.GetValueOrDefault(Height), culture);
-            return rotated ? new Size(height, width) : new Size(width, height);
+
+            return IsExifOrientationRotated(orientation)
+                ? new Size(height, width)
+                : new Size(width, height);
         }
 
         private static PointF? GetCenter(
@@ -345,23 +348,32 @@ private static IResampler GetSampler(CommandCollection commands)
             return KnownResamplers.Bicubic;
         }
 
-        private static bool ShouldHandleExifRotation(FormattedImage image, CommandCollection commands, CommandParser parser, CultureInfo culture, out ushort orientation)
+        private static ushort GetExifOrientation(FormattedImage image, CommandCollection commands, CommandParser parser, CultureInfo culture)
         {
             // Browsers now implement 'image-orientation: from-image' by default.
             // https://developer.mozilla.org/en-US/docs/web/css/image-orientation
             // This makes orientation handling confusing for users who expect images to be resized in accordance
             // to what they observe rather than pure (and correct) methods.
             //
-            // To accomodate this we parse the dimensions to use based upon decoded EXIF orientation values, switching
-            // the width/height parameters when images are rotated (not flipped).
+            // To accomodate this we parse the dimensions to use based upon decoded EXIF orientation values.
             // We default to 'true' for EXIF orientation handling. By passing 'false' it can be turned off.
             if (commands.Contains(Orient) && !parser.ParseValue<bool>(commands.GetValueOrDefault(Orient), culture))
             {
-                orientation = ExifOrientationMode.Unknown;
-                return false;
+                return ExifOrientationMode.Unknown;
             }
 
-            return image.IsExifRotated(out orientation);
+            image.TryGetExifOrientation(out ushort orientation);
+            return orientation;
         }
+
+        private static bool IsExifOrientationRotated(ushort orientation)
+            => orientation switch
+            {
+                ExifOrientationMode.LeftTop
+                or ExifOrientationMode.RightTop
+                or ExifOrientationMode.RightBottom
+                or ExifOrientationMode.LeftBottom => true,
+                _ => false,
+            };
     }
 }