Add tests for writing IPTC

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -623,17 +623,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 return;
             }
 
-            var identifier = new byte[ProfileResolver.AdobePhotoshopApp13Marker.Length];
-            this.InputStream.Read(identifier, 0, identifier.Length);
-            remaining -= identifier.Length;
-            if (ProfileResolver.IsProfile(identifier, ProfileResolver.AdobePhotoshopApp13Marker))
+            this.InputStream.Read(this.temp, 0, ProfileResolver.AdobePhotoshopApp13Marker.Length);
+            remaining -= ProfileResolver.AdobePhotoshopApp13Marker.Length;
+            if (ProfileResolver.IsProfile(this.temp, ProfileResolver.AdobePhotoshopApp13Marker))
             {
                 var resourceBlockData = new byte[remaining];
                 this.InputStream.Read(resourceBlockData, 0, remaining);
                 Span<byte> blockDataSpan = resourceBlockData.AsSpan();
 
-                while (blockDataSpan.Length > 10)
-                 {
+                while (blockDataSpan.Length > 12)
+                {
                     if (!ProfileResolver.IsProfile(blockDataSpan.Slice(0, 4), ProfileResolver.AdobeImageResourceBlockMarker))
                     {
                         return;

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -233,7 +233,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             // Write the Start Of Image marker.
             this.WriteApplicationHeader(metadata);
 
-            // Write Exif and ICC profiles
+            // Write Exif, ICC and IPTC profiles
             this.WriteProfiles(metadata);
 
             // Write the quantization tables.
@@ -708,18 +708,21 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             }
 
             iptcProfile.UpdateData();
-            var data = iptcProfile.Data;
+            byte[] data = iptcProfile.Data;
             if (data.Length == 0)
             {
                 return;
             }
 
-            var app13length = data.Length + ProfileResolver.AdobeImageResourceBlockMarker.Length + ProfileResolver.AdobeIptcMarker.Length + 2 + 4;
-            this.WriteAppHeader(app13length, JpegConstants.Markers.APP13);
-            this.outputStream.Write(this.buffer, 0, 4);
+            var app13Length = 2 + ProfileResolver.AdobePhotoshopApp13Marker.Length +
+                              ProfileResolver.AdobeImageResourceBlockMarker.Length +
+                              ProfileResolver.AdobeIptcMarker.Length +
+                              2 + 4 + data.Length;
+            this.WriteAppHeader(app13Length, JpegConstants.Markers.APP13);
+            this.outputStream.Write(ProfileResolver.AdobePhotoshopApp13Marker);
             this.outputStream.Write(ProfileResolver.AdobeImageResourceBlockMarker);
             this.outputStream.Write(ProfileResolver.AdobeIptcMarker);
-            this.outputStream.WriteByte(0); // a null name consists of two bytes of 0.
+            this.outputStream.WriteByte(0); // a empty pascal string (padded to make size even)
             this.outputStream.WriteByte(0);
             BinaryPrimitives.WriteInt32BigEndian(this.buffer, data.Length);
             this.outputStream.Write(this.buffer, 0, 4);

tests/ImageSharp.Tests/Metadata/Profiles/IPTC/IptcProfileTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.Metadata.Profiles.Iptc;
@@ -16,13 +17,13 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.IPTC
 
         [Theory]
         [WithFile(TestImages.Jpeg.Baseline.Iptc, PixelTypes.Rgba32)]
-        public void ReadIptcProfile<TPixel>(TestImageProvider<TPixel> provider)
+        public void ReadIptcMetadata_Works<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             using (Image<TPixel> image = provider.GetImage(JpegDecoder))
             {
                 Assert.NotNull(image.Metadata.IptcProfile);
-                IEnumerable<IptcValue> iptcValues = image.Metadata.IptcProfile.Values;
+                var iptcValues = image.Metadata.IptcProfile.Values.ToList();
                 ContainsIptcValue(iptcValues, IptcTag.Caption, "description");
                 ContainsIptcValue(iptcValues, IptcTag.CaptionWriter, "description writer");
                 ContainsIptcValue(iptcValues, IptcTag.Headline, "headline");
@@ -44,6 +45,27 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.IPTC
             }
         }
 
+        [Fact]
+        public void IptcProfile_ToAndFromByteArray_Works()
+        {
+            // arrange
+            var profile = new IptcProfile();
+            var expectedCaptionWriter = "unittest";
+            var expectedCaption = "test";
+            profile.SetValue(IptcTag.CaptionWriter, expectedCaptionWriter);
+            profile.SetValue(IptcTag.Caption, expectedCaption);
+
+            // act
+            profile.UpdateData();
+            byte[] profileBytes = profile.Data;
+            var profileFromBytes = new IptcProfile(profileBytes);
+
+            // assert
+            var iptcValues = profileFromBytes.Values.ToList();
+            ContainsIptcValue(iptcValues, IptcTag.CaptionWriter, expectedCaptionWriter);
+            ContainsIptcValue(iptcValues, IptcTag.Caption, expectedCaption);
+        }
+
         [Fact]
         public void IptcProfile_CloneIsDeep()
         {
@@ -79,10 +101,44 @@ namespace SixLabors.ImageSharp.Tests.Metadata.Profiles.IPTC
             Assert.NotEqual(iptcValue.Value, clone.Value);
         }
 
+        [Fact]
+        public void WritingImage_PreservesIptcProfile()
+        {
+            // arrange
+            var image = new Image<Rgba32>(1, 1);
+            image.Metadata.IptcProfile = new IptcProfile();
+            var expectedCaptionWriter = "unittest";
+            var expectedCaption = "test";
+            image.Metadata.IptcProfile.SetValue(IptcTag.CaptionWriter, expectedCaptionWriter);
+            image.Metadata.IptcProfile.SetValue(IptcTag.Caption, expectedCaption);
+
+            // act
+            Image<Rgba32> reloadedImage = WriteAndReadJpeg(image);
+
+            // assert
+            IptcProfile actual = reloadedImage.Metadata.IptcProfile;
+            Assert.NotNull(actual);
+            var iptcValues = actual.Values.ToList();
+            ContainsIptcValue(iptcValues, IptcTag.CaptionWriter, expectedCaptionWriter);
+            ContainsIptcValue(iptcValues, IptcTag.Caption, expectedCaption);
+        }
+
         private static void ContainsIptcValue(IEnumerable<IptcValue> values, IptcTag tag, string value)
         {
             Assert.True(values.Any(val => val.Tag == tag), $"Missing iptc tag {tag}");
             Assert.True(values.Contains(new IptcValue(tag, System.Text.Encoding.UTF8.GetBytes(value))), $"expected iptc value '{value}' was not found for tag '{tag}'");
         }
+
+        private static Image<Rgba32> WriteAndReadJpeg(Image<Rgba32> image)
+        {
+            using (var memStream = new MemoryStream())
+            {
+                image.SaveAsJpeg(memStream);
+                image.Dispose();
+
+                memStream.Position = 0;
+                return Image.Load<Rgba32>(memStream);
+            }
+        }
     }
 }