Fix IPTC tags written on jpg files that contains non-English characters can't be correctly displayed on external apps #2212

src/ImageSharp/Metadata/Profiles/IPTC/IptcProfile.cs

@@ -20,6 +20,16 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
 
         private const uint MaxStandardDataTagSize = 0x7FFF;
 
+        /// <summary>
+        /// 1:90 Coded Character Set
+        /// </summary>
+        private const byte IptcEnvelopeCodedCharacterSet = 0x5A;
+
+        /// <summary>
+        /// This value marks that UTF-8 encoding is used in application records
+        /// </summary>
+        private static readonly byte[] CodedCharacterSetUtf8Value = { 0x1B, 0x25, 0x47 };
+
         /// <summary>
         /// Initializes a new instance of the <see cref="IptcProfile"/> class.
         /// </summary>
@@ -194,6 +204,17 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
             this.values.Add(new IptcValue(tag, encoding, value, strict));
         }
 
+        /// <summary>
+        /// Sets the value of the specified tag.
+        /// </summary>
+        /// <param name="tag">The tag of the iptc value.</param>
+        /// <param name="value">The value.</param>
+        /// <param name="strict">
+        /// Indicates if length restrictions from the specification should be followed strictly.
+        /// Defaults to true.
+        /// </param>
+        public void SetValue(IptcTag tag, string value, bool strict = true) => this.SetValue(tag, Encoding.UTF8, value, strict);
+
         /// <summary>
         /// Makes sure the datetime is formatted according to the iptc specification.
         /// <example>
@@ -219,17 +240,6 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
             this.SetValue(tag, Encoding.UTF8, formattedDate);
         }
 
-        /// <summary>
-        /// Sets the value of the specified tag.
-        /// </summary>
-        /// <param name="tag">The tag of the iptc value.</param>
-        /// <param name="value">The value.</param>
-        /// <param name="strict">
-        /// Indicates if length restrictions from the specification should be followed strictly.
-        /// Defaults to true.
-        /// </param>
-        public void SetValue(IptcTag tag, string value, bool strict = true) => this.SetValue(tag, Encoding.UTF8, value, strict);
-
         /// <summary>
         /// Updates the data of the profile.
         /// </summary>
@@ -241,9 +251,28 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
                 length += value.Length + 5;
             }
 
-            this.Data = new byte[length];
+            bool hasValuesInUtf8 = this.HasValuesInUtf8();
+
+            if (hasValuesInUtf8)
+            {
+                length += 5 + CodedCharacterSetUtf8Value.Length; // additional length for UTF-8 Tag
+            }
 
+            this.Data = new byte[length];
             int i = 0;
+
+            if (hasValuesInUtf8)
+            {
+                // Standard DataSet Tag
+                this.Data[i++] = IptcTagMarkerByte;
+                this.Data[i++] = 1; // Envelope
+                this.Data[i++] = IptcEnvelopeCodedCharacterSet;
+                this.Data[i++] = (byte)(CodedCharacterSetUtf8Value.Length >> 8);
+                this.Data[i++] = (byte)CodedCharacterSetUtf8Value.Length;
+                Buffer.BlockCopy(CodedCharacterSetUtf8Value, 0, this.Data, i, CodedCharacterSetUtf8Value.Length);
+                i += CodedCharacterSetUtf8Value.Length;
+            }
+
             foreach (IptcValue value in this.Values)
             {
                 // Standard DataSet Tag
@@ -264,7 +293,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
                 // |           |                | octet 4(most significant bit) always will be 0.                                 |
                 // +-----------+----------------+---------------------------------------------------------------------------------+
                 this.Data[i++] = IptcTagMarkerByte;
-                this.Data[i++] = 2;
+                this.Data[i++] = 2; // Application
                 this.Data[i++] = (byte)value.Tag;
                 this.Data[i++] = (byte)(value.Length >> 8);
                 this.Data[i++] = (byte)value.Length;
@@ -309,7 +338,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
 
                 if (isValidEntry && byteCount > 0 && (offset <= this.Data.Length - byteCount))
                 {
-                    var iptcData = new byte[byteCount];
+                    byte[] iptcData = new byte[byteCount];
                     Buffer.BlockCopy(this.Data, offset, iptcData, 0, (int)byteCount);
                     this.values.Add(new IptcValue(tag, iptcData, false));
                 }
@@ -317,5 +346,22 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
                 offset += (int)byteCount;
             }
         }
+
+        /// <summary>
+        /// Gets if any value has UTF-8 encoding
+        /// </summary>
+        /// <returns>true if any value has UTF-8 encoding</returns>
+        private bool HasValuesInUtf8()
+        {
+            foreach (IptcValue value in this.values)
+            {
+                if (value.Encoding == Encoding.UTF8)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
     }
 }