More HIF support

src/ImageSharp/Formats/Heic/Heic4CharCode.cs

@@ -223,4 +223,9 @@ public enum Heic4CharCode : uint
     /// </summary>
     uuid = 0x75756964U,
 
+    /// <summary>
+    /// Free space.
+    /// </summary>
+    free = 0x66726565U,
+
 }

src/ImageSharp/Formats/Heic/Heic4CharCode.tt

@@ -49,6 +49,7 @@
         "uri ", "URI",
         "pict", "Picture handler type",
         "uuid", "Unique Identifier",
+        "free", "Free space",
     };
 #>
 

src/ImageSharp/Formats/Heic/HeicConstants.cs

@@ -18,5 +18,5 @@ internal static class HeicConstants
     /// <summary>
     /// The list of file extensions that equate to a HEIC.
     /// </summary>
-    public static readonly IEnumerable<string> FileExtensions = new[] { "heic", "heif", "avif" };
+    public static readonly IEnumerable<string> FileExtensions = new[] { "heic", "heif", "hif", "avif" };
 }

src/ImageSharp/Formats/Heic/HeicDecoderCore.cs

@@ -75,8 +75,15 @@ internal sealed class HeicDecoderCore : IImageDecoderInternals
                 case Heic4CharCode.mdat:
                     this.ParseMediaData(stream, boxLength);
                     break;
+                case Heic4CharCode.free:
+                    SkipBox(stream, boxLength);
+                    break;
+                case 0U:
+                    // Some files have trailing zeros, skiping to EOF.
+                    stream.Skip((int)(stream.Length - stream.Position));
+                    break;
                 default:
-                    throw new ImageFormatException($"Unknown box type of '{Enum.GetName(boxType)}'");
+                    throw new ImageFormatException($"Unknown box type of '{PrettyPrint(boxType)}'");
             }
         }
 
@@ -129,9 +136,10 @@ internal sealed class HeicDecoderCore : IImageDecoderInternals
         long boxLength = this.ReadBoxHeader(stream, out Heic4CharCode boxType);
         Span<byte> buffer = this.ReadIntoBuffer(stream, boxLength);
         uint majorBrand = BinaryPrimitives.ReadUInt32BigEndian(buffer);
+        bool correctBrand = majorBrand == (uint)Heic4CharCode.heic || majorBrand == (uint)Heic4CharCode.heix;
 
         // TODO: Interpret minorVersion and compatible brands.
-        return boxType == Heic4CharCode.ftyp && majorBrand == (uint)Heic4CharCode.heic;
+        return boxType == Heic4CharCode.ftyp && correctBrand;
     }
 
     private long ReadBoxHeader(BufferedReadStream stream, out Heic4CharCode boxType)
@@ -490,6 +498,7 @@ internal sealed class HeicDecoderCore : IImageDecoderInternals
         for (uint i = 0; i < itemCount; i++)
         {
             uint itemId = ReadUInt16Or32(buffer, version == 2, ref bytesRead);
+            HeicItem? item = this.FindItemById(itemId);
             if (version is 1 or 2)
             {
                 bytesRead++;
@@ -506,11 +515,13 @@ internal sealed class HeicDecoderCore : IImageDecoderInternals
             {
                 if (version is 1 or 2 && indexSize > 0)
                 {
-                    ulong extentIndex = ReadUIntVariable(buffer, indexSize, ref bytesRead);
+                    _ = ReadUIntVariable(buffer, indexSize, ref bytesRead);
                 }
 
                 ulong extentOffset = ReadUIntVariable(buffer, offsetSize, ref bytesRead);
                 ulong extentLength = ReadUIntVariable(buffer, lengthSize, ref bytesRead);
+                HeicLocation loc = new HeicLocation((long)extentOffset, (long)extentLength);
+                item?.DataLocations.Add(loc);
             }
         }
     }

src/ImageSharp/Formats/Heic/HeicItem.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+
 namespace SixLabors.ImageSharp.Formats.Heic;
 
 /// <summary>
@@ -68,6 +69,11 @@ public class HeicItem(Heic4CharCode type, uint id)
     /// </summary>
     public Size GridCellExtent { get; private set; }
 
+    /// <summary>
+    /// Gets the list of data locations for this item.
+    /// </summary>
+    public List<HeicLocation> DataLocations { get; } = new List<HeicLocation>();
+
     /// <summary>
     /// Set the image extent.
     /// </summary>

src/ImageSharp/Formats/Heic/HeicLocation.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Heic;
+
+/// <summary>
+/// Location within the file of an <see cref="HeicItem"/>.
+/// </summary>
+public class HeicLocation(long offset, long length)
+{
+    /// <summary>
+    /// Gets the file offset of this location.
+    /// </summary>
+    public long Offset { get; } = offset;
+
+    /// <summary>
+    /// Gets the length of this location.
+    /// </summary>
+    public long Length { get; } = length;
+}