From 3aa00199f1d9aba96da203347a4d2277b1e64ec7 Mon Sep 17 00:00:00 2001
From: popow <popow@gmx.de>
Date: Sun, 17 Jun 2018 14:46:28 +0200
Subject: [PATCH] ToByteArray skips the first 6 bytes if includeExifCode is
 false, added unit test for that

---
 .../MetaData/Profiles/Exif/ExifProfile.cs     | 33 +++++++++++++++++++
 .../Profiles/Exif/ExifProfileTests.cs         | 26 +++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/src/ImageSharp/MetaData/Profiles/Exif/ExifProfile.cs b/src/ImageSharp/MetaData/Profiles/Exif/ExifProfile.cs
index 5ba1946349..4a73e8a4be 100644
--- a/src/ImageSharp/MetaData/Profiles/Exif/ExifProfile.cs
+++ b/src/ImageSharp/MetaData/Profiles/Exif/ExifProfile.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Primitives;
 
@@ -239,6 +240,12 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
         {
             if (this.values == null)
             {
+                if (!includeExifIdCode && this.StartsWithExifIdCode(this.data))
+                {
+                    // skip the first 6 bytes (the Exif Code)
+                    return this.data.Skip(6).ToArray();
+                }
+
                 return this.data;
             }
 
@@ -251,6 +258,32 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
             return writer.GetData(includeExifIdCode);
         }
 
+        /// <summary>
+        /// Checks if a byte array start with the Exif Code: ASCII "Exif" followed by two zeros.
+        /// </summary>
+        /// <param name="exifBytes">The byte array to check for the Exif Code.</param>
+        /// <returns>True, if the byte array starts with the Exif Code</returns>
+        private bool StartsWithExifIdCode(byte[] exifBytes)
+        {
+            if (exifBytes.Length < 6)
+            {
+                return false;
+            }
+
+            // The EXIF ID code: ASCII "Exif" followed by two zeros.
+            byte[] exifCode = { 69, 120, 105, 102, 0, 0 };
+            int exifLength = exifCode.Length;
+            for (int i = 0; i < exifCode.Length; i++)
+            {
+                if (exifBytes[i] != exifCode[i])
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
         /// <summary>
         /// Synchronizes the profiles with the specified meta data.
         /// </summary>
diff --git a/tests/ImageSharp.Tests/MetaData/Profiles/Exif/ExifProfileTests.cs b/tests/ImageSharp.Tests/MetaData/Profiles/Exif/ExifProfileTests.cs
index 6d3eb56317..98113f3921 100644
--- a/tests/ImageSharp.Tests/MetaData/Profiles/Exif/ExifProfileTests.cs
+++ b/tests/ImageSharp.Tests/MetaData/Profiles/Exif/ExifProfileTests.cs
@@ -351,6 +351,32 @@ namespace SixLabors.ImageSharp.Tests
             }
         }
 
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void TestProfileToByteArrayWorks(bool includeExifIdCode)
+        {
+            // arrange
+            byte[] exifBytesWithExifCode = new byte[] { 69, 120, 105, 102, 0, 0, 73, 73, 42, 0};
+            byte[] exifBytesWithoutExifCode = new byte[] { 73, 73, 42, 0 };
+            var profile = new ExifProfile(exifBytesWithExifCode);
+
+            // act
+            byte[] actual = profile.ToByteArray(includeExifIdCode);
+
+            // assert
+            Assert.NotNull(actual);
+            Assert.NotEmpty(actual);
+            if (includeExifIdCode)
+            {
+                Assert.Equal(exifBytesWithExifCode, actual);
+            }
+            else
+            {
+                Assert.Equal(exifBytesWithoutExifCode, actual);
+            }
+        }
+
         private static ExifProfile CreateExifProfile()
         {
             var profile = new ExifProfile();