Add some code comments

src/ImageSharp/Formats/Heif/Av1/Readme.md

@@ -41,7 +41,11 @@ Paritions can contain other partitions and blocks.
 
 ## Block
 
-A block is the smallest are of the image which has the same transformation parameters. A block contains ore or more ModeInfos.
+
+## Transform Block
+
+A Transform Block is the smallest area of the image, which has the same transformation parameters. A block contains ore or more ModeInfos.
+
 
 ## ModeInfo
 

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1FrameBuffer.cs

@@ -61,9 +61,6 @@ internal class Av1FrameBuffer
                 this.superblockInfos[i] = new(this, point);
                 for (int u = 0; u < this.modeInfoSizePerSuperblock; u++)
                 {
-                    this.transformInfosY[j] = new Av1TransformInfo();
-                    this.transformInfosY[j << 1] = new Av1TransformInfo();
-                    this.transformInfosY[(j << 1) + 1] = new Av1TransformInfo();
                     for (int v = 0; v < this.modeInfoSizePerSuperblock; v++)
                     {
                         this.modeInfos[k] = new Av1BlockModeInfo(numPlanes, Av1BlockSize.Block4x4, new Point(u, v));

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1PartitionInfo.cs

@@ -17,29 +17,50 @@ internal class Av1PartitionInfo
         this.ModeInfo = modeInfo;
         this.SuperblockInfo = superblockInfo;
         this.IsChroma = isChroma;
-        this.PartitionType = partitionType;
+        this.Type = partitionType;
         this.CdefStrength = [];
         this.ReferenceFrame = [-1, -1];
     }
 
     public Av1BlockModeInfo ModeInfo { get; }
 
+    /// <summary>
+    /// Gets the <see cref="Av1SuperblockInfo"/> this partition resides inside.
+    /// </summary>
     public Av1SuperblockInfo SuperblockInfo { get; }
 
     public bool IsChroma { get; }
 
-    public Av1PartitionType PartitionType { get; }
+    public Av1PartitionType Type { get; }
 
-    public bool AvailableUp { get; set; }
+    /// <summary>
+    /// Gets or sets a value indicating whether the information from the block above can be used on the luma plane.
+    /// </summary>
+    public bool AvailableAbove { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether the information from the block left can be used on the luma plane.
+    /// </summary>
     public bool AvailableLeft { get; set; }
 
-    public bool AvailableUpForChroma { get; set; }
+    /// <summary>
+    /// Gets or sets a value indicating whether the information from the block above can be used on the chroma plane.
+    /// </summary>
+    public bool AvailableAboveForChroma { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether the information from the block left can be used on the chroma plane.
+    /// </summary>
     public bool AvailableLeftForChroma { get; set; }
 
+    /// <summary>
+    /// Gets or sets the horizontal location of the block in units of 4x4 luma samples.
+    /// </summary>
     public int ColumnIndex { get; set; }
 
+    /// <summary>
+    /// Gets or sets the vertical location of the block in units of 4x4 luma samples.
+    /// </summary>
     public int RowIndex { get; set; }
 
     public Av1BlockModeInfo? AboveModeInfo { get; set; }
@@ -59,9 +80,9 @@ internal class Av1PartitionInfo
         Av1BlockSize blockSize = this.ModeInfo.BlockSize;
         int bw4 = blockSize.Get4x4WideCount();
         int bh4 = blockSize.Get4x4HighCount();
-        this.AvailableUp = this.RowIndex > tileInfo.ModeInfoRowStart;
+        this.AvailableAbove = this.RowIndex > tileInfo.ModeInfoRowStart;
         this.AvailableLeft = this.ColumnIndex > tileInfo.ModeInfoColumnStart;
-        this.AvailableUpForChroma = this.AvailableUp;
+        this.AvailableAboveForChroma = this.AvailableAbove;
         this.AvailableLeftForChroma = this.AvailableLeft;
         this.modeBlockToLeftEdge = -(this.ColumnIndex << Av1Constants.ModeInfoSizeLog2) << 3;
         this.modeBlockToRightEdge = ((frameInfo.ModeInfoColumnCount - bw4 - this.ColumnIndex) << Av1Constants.ModeInfoSizeLog2) << 3;

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileDecoder.cs

@@ -346,7 +346,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
         {
             if (this.SequenceHeader.ColorConfig.SubSamplingY && block4x4Height == 1)
             {
-                partitionInfo.AvailableUpForChroma = this.IsInside(rowIndex - 2, columnIndex);
+                partitionInfo.AvailableAboveForChroma = this.IsInside(rowIndex - 2, columnIndex);
             }
 
             if (this.SequenceHeader.ColorConfig.SubSamplingX && block4x4Width == 1)
@@ -355,7 +355,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
             }
         }
 
-        if (partitionInfo.AvailableUp)
+        if (partitionInfo.AvailableAbove)
         {
             partitionInfo.AboveModeInfo = superblockInfo.GetModeInfo(new Point(rowIndex - 1, columnIndex));
         }
@@ -456,8 +456,8 @@ internal class Av1TileDecoder : IAv1TileDecoder
                         int coefficientIndex = this.coefficientIndex[plane];
                         int endOfBlock = 0;
                         Av1TransformInfo transformInfo = this.FrameBuffer.GetTransform(plane, transformInfoIndices[plane])!;
-                        int blockColumn = transformInfo.TransformOffsetX;
+                        int blockColumn = transformInfo.OffsetX;
-                        int blockRow = transformInfo.TransformOffsetY;
+                        int blockRow = transformInfo.OffsetY;
                         int startX = (partitionInfo.ColumnIndex >> subX) + blockColumn;
                         int startY = (partitionInfo.RowIndex >> subY) + blockRow;
 
@@ -469,7 +469,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
 
                         if (!partitionInfo.ModeInfo.Skip)
                         {
-                            endOfBlock = this.TransformBlock(ref reader, partitionInfo, coefficientIndex, transformInfo, plane, blockColumn, blockRow, startX, startY, transformInfo.TransformSize, subX != 0, subY != 0);
+                            endOfBlock = this.TransformBlock(ref reader, partitionInfo, coefficientIndex, transformInfo, plane, blockColumn, blockRow, startX, startY, transformInfo.Size, subX != 0, subY != 0);
                         }
 
                         if (endOfBlock != 0)
@@ -824,7 +824,7 @@ internal class Av1TileDecoder : IAv1TileDecoder
         int above = (aboveWidth >= maxTransformSize.GetWidth()) ? 1 : 0;
         int leftHeight = this.leftNeighborContext.LeftTransformHeight[partitionInfo.RowIndex - superblockInfo.Position.Y];
         int left = (leftHeight >= maxTransformSize.GetHeight()) ? 1 : 0;
-        bool hasAbove = partitionInfo.AvailableUp;
+        bool hasAbove = partitionInfo.AvailableAbove;
         bool hasLeft = partitionInfo.AvailableLeft;
 
         if (hasAbove && hasLeft)
@@ -902,12 +902,8 @@ internal class Av1TileDecoder : IAv1TileDecoder
                 {
                     for (int blockColumn = idx; blockColumn < unitWidth; blockColumn += stepColumn)
                     {
-                        this.FrameBuffer.SetTransformY(transformInfoYIndex, new Av1TransformInfo
+                        this.FrameBuffer.SetTransformY(transformInfoYIndex, new Av1TransformInfo(
-                        {
+                            transformSize, blockColumn, blockRow));
-                            TransformSize = transformSize,
-                            OffsetX = blockColumn,
-                            OffsetY = blockRow
-                        });
                         transformInfoYIndex++;
                         lumaTusCount++;
                         totalLumaTusCount++;
@@ -931,12 +927,8 @@ internal class Av1TileDecoder : IAv1TileDecoder
                 {
                     for (int blockColumn = idx; blockColumn < unitWidth; blockColumn += stepColumn)
                     {
-                        this.FrameBuffer.SetTransformUv(transformInfoUvIndex, new Av1TransformInfo
+                        this.FrameBuffer.SetTransformUv(transformInfoUvIndex, new Av1TransformInfo(
-                        {
+                            transformSizeUv, blockColumn, blockRow));
-                            TransformSize = transformSizeUv,
-                            OffsetX = blockColumn,
-                            OffsetY = blockRow
-                        });
                         transformInfoUvIndex++;
                         chromaTusCount++;
                         totalChromaTusCount++;
@@ -1176,12 +1168,12 @@ internal class Av1TileDecoder : IAv1TileDecoder
         int prevL = -1;
         int columnIndex = partitionInfo.ColumnIndex;
         int rowIndex = partitionInfo.RowIndex;
-        if (partitionInfo.AvailableUp && partitionInfo.AvailableLeft)
+        if (partitionInfo.AvailableAbove && partitionInfo.AvailableLeft)
         {
             prevUL = this.GetSegmentId(partitionInfo, rowIndex - 1, columnIndex - 1);
         }
 
-        if (partitionInfo.AvailableUp)
+        if (partitionInfo.AvailableAbove)
         {
             prevU = this.GetSegmentId(partitionInfo, rowIndex - 1, columnIndex);
         }

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TransformInfo.cs

@@ -5,28 +5,64 @@ using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
 
 namespace SixLabors.ImageSharp.Formats.Heif.Av1.Symbol;
 
+/// <summary>
+/// Information of a single Transform Block.
+/// </summary>
 internal class Av1TransformInfo
 {
-    public Av1TransformInfo()
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Av1TransformInfo"/> class.
+    /// </summary>
+    public Av1TransformInfo(Av1TransformSize size, int offsetX, int offsetY)
     {
+        this.Size = size;
+        this.OffsetX = offsetX;
+        this.OffsetY = offsetY;
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Av1TransformInfo"/> class.
+    /// </summary>
+    /// <param name="originalInfo">The <see cref="Av1TransformInfo"/> to copy the information from.</param>
     public Av1TransformInfo(Av1TransformInfo originalInfo)
     {
-        this.TransformSize = originalInfo.TransformSize;
+        this.Size = originalInfo.Size;
         this.OffsetX = originalInfo.OffsetX;
         this.OffsetY = originalInfo.OffsetY;
     }
 
-    public Av1TransformSize TransformSize { get; internal set; }
+    /// <summary>
+    /// Gets or sets the transform size to be used for this Transform Block.
+    /// </summary>
+    public Av1TransformSize Size { get; internal set; }
 
+    /// <summary>
+    /// Gets or sets the transform type to be used for this Transform Block.
+    /// </summary>
+    public Av1TransformType Type { get; internal set; }
+
+    /// <summary>
+    /// Gets or sets the X offset of this block in ModeInfo units.
+    /// </summary>
     public int OffsetX { get; internal set; }
 
+    /// <summary>
+    /// Gets or sets the Y offset of this block in ModeInfo units.
+    /// </summary>
     public int OffsetY { get; internal set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether the Code block flag is set.
+    /// <list type="table">
+    /// <item>
+    /// <term>false</term>
+    /// <description>No residual for the block</description>
+    /// </item>
+    /// <item>
+    /// <term>true</term>
+    /// <description>Residual exists for the block</description>
+    /// </item>
+    /// </list>
+    /// </summary>
     public bool CodeBlockFlag { get; internal set; }
-
-    public int TransformOffsetX { get; internal set; }
-
-    public int TransformOffsetY { get; internal set; }
 }

tests/ImageSharp.Tests/Formats/Heif/Av1/Av1TilingTests.cs

@@ -10,7 +10,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
 [Trait("Format", "Avif")]
 public class Av1TilingTests
 {
-    // [Theory]
+    [Theory]
     [InlineData(TestImages.Heif.XnConvert, 0x010E, 0x03CC, 18, 0x03CC - 18)]
     public void ReadFirstTile(string filename, int headerOffset, int headerSize, int tileOffset, int tileSize)
     {