Bug fixes to partition parsing

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1FrameInfo.cs

@@ -48,7 +48,7 @@ internal partial class Av1FrameInfo
         // Allocate the arrays.
         this.superblockInfos = new Av1SuperblockInfo[superblockCount];
         this.modeInfos = new Av1BlockModeInfo[superblockCount * this.modeInfoCountPerSuperblock];
-        this.modeInfoMap = new Av1FrameModeInfoMap(new Size(this.modeInfoCountPerSuperblock * this.superblockColumnCount, this.modeInfoCountPerSuperblock * this.superblockRowCount), superblockSizeLog2);
+        this.modeInfoMap = new Av1FrameModeInfoMap(new Size(this.modeInfoSizePerSuperblock * this.superblockColumnCount, this.modeInfoSizePerSuperblock * this.superblockRowCount), superblockSizeLog2);
         this.transformInfosY = new Av1TransformInfo[superblockCount * this.modeInfoCountPerSuperblock];
         this.transformInfosUv = new Av1TransformInfo[2 * superblockCount * this.modeInfoCountPerSuperblock];
 

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1ParseAboveNeighbor4x4Context.cs

@@ -64,9 +64,9 @@ internal class Av1ParseAboveNeighbor4x4Context
         Array.Fill(this.aboveCompGroupIndex, 0, 0, width);
     }
 
-    public void UpdatePartition(Point modeInfoLocation, Av1TileInfo tileLoc, Av1BlockSize subSize, Av1BlockSize blockSize)
+    public void UpdatePartition(Point modeInfoLocation, Av1TileInfo tileInfo, Av1BlockSize subSize, Av1BlockSize blockSize)
     {
-        int startIndex = modeInfoLocation.X - tileLoc.ModeInfoColumnStart;
+        int startIndex = modeInfoLocation.X - tileInfo.ModeInfoColumnStart;
         int bw = blockSize.Get4x4WideCount();
         int value = Av1PartitionContext.GetAboveContext(subSize);
 

src/ImageSharp/Formats/Heif/Av1/Tiling/Av1TileReader.cs

@@ -187,8 +187,8 @@ internal class Av1TileReader : IAv1TileReader
         switch (partitionType)
         {
             case Av1PartitionType.Split:
-                Point loc1 = new(modeInfoLocation.X, modeInfoLocation.Y + halfBlock4x4Size);
-                Point loc2 = new(modeInfoLocation.X + halfBlock4x4Size, modeInfoLocation.Y);
+                Point loc1 = new(modeInfoLocation.X + halfBlock4x4Size, modeInfoLocation.Y);
+                Point loc2 = new(modeInfoLocation.X, modeInfoLocation.Y + halfBlock4x4Size);
                 Point loc3 = new(modeInfoLocation.X + halfBlock4x4Size, modeInfoLocation.Y + halfBlock4x4Size);
                 this.ParsePartition(ref reader, modeInfoLocation, subSize, superblockInfo, tileInfo);
                 this.ParsePartition(ref reader, loc1, subSize, superblockInfo, tileInfo);
@@ -248,7 +248,7 @@ internal class Av1TileReader : IAv1TileReader
                 for (int i = 0; i < 4; i++)
                 {
                     int currentBlockRow = rowIndex + (i * quarterBlock4x4Size);
-                    if (i > 0 && currentBlockRow > this.FrameHeader.ModeInfoRowCount)
+                    if (i > 0 && currentBlockRow >= this.FrameHeader.ModeInfoRowCount)
                     {
                         break;
                     }
@@ -262,7 +262,7 @@ internal class Av1TileReader : IAv1TileReader
                 for (int i = 0; i < 4; i++)
                 {
                     int currentBlockColumn = columnIndex + (i * quarterBlock4x4Size);
-                    if (i > 0 && currentBlockColumn > this.FrameHeader.ModeInfoColumnCount)
+                    if (i > 0 && currentBlockColumn >= this.FrameHeader.ModeInfoColumnCount)
                     {
                         break;
                     }
@@ -338,7 +338,7 @@ internal class Av1TileReader : IAv1TileReader
         this.ReadBlockTransformSize(ref reader, modeInfoLocation, partitionInfo, superblockInfo, tileInfo);
         if (partitionInfo.ModeInfo.Skip)
         {
-            this.ResetSkipContext(partitionInfo);
+            this.ResetSkipContext(partitionInfo, tileInfo);
         }
 
         this.Residual(ref reader, partitionInfo, superblockInfo, tileInfo, blockSize);
@@ -347,7 +347,10 @@ internal class Av1TileReader : IAv1TileReader
         this.FrameInfo.UpdateModeInfo(blockModeInfo, superblockInfo);
     }
 
-    private void ResetSkipContext(Av1PartitionInfo partitionInfo)
+    /// <summary>
+    /// SVT: reset_skip_context
+    /// </summary>
+    private void ResetSkipContext(Av1PartitionInfo partitionInfo, Av1TileInfo tileInfo)
     {
         int planesCount = this.SequenceHeader.ColorConfig.PlaneCount;
         for (int i = 0; i < planesCount; i++)
@@ -358,8 +361,8 @@ internal class Av1TileReader : IAv1TileReader
             DebugGuard.IsTrue(planeBlockSize != Av1BlockSize.Invalid, nameof(planeBlockSize));
             int txsWide = planeBlockSize.GetWidth() >> 2;
             int txsHigh = planeBlockSize.GetHeight() >> 2;
-            int aboveOffset = (partitionInfo.ColumnIndex - this.FrameHeader.TilesInfo.TileColumnStartModeInfo[partitionInfo.ColumnIndex]) >> subX;
-            int leftOffset = (partitionInfo.RowIndex - this.FrameHeader.TilesInfo.TileRowStartModeInfo[partitionInfo.RowIndex]) >> subY;
+            int aboveOffset = (partitionInfo.ColumnIndex - tileInfo.ModeInfoColumnStart) >> subX;
+            int leftOffset = (partitionInfo.RowIndex - partitionInfo.SuperblockInfo.Position.Y) >> subY;
             this.aboveNeighborContext.ClearContext(i, aboveOffset, txsWide);
             this.leftNeighborContext.ClearContext(i, leftOffset, txsHigh);
         }

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

@@ -11,8 +11,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
 public class Av1TilingTests
 {
     [Theory]
-    /*[InlineData(TestImages.Heif.XnConvert, 0x010E, 0x03CC, 18)]*/
-    [InlineData(TestImages.Heif.Orange4x4, 0x010E, 0x001d, 21)]
+    [InlineData(TestImages.Heif.XnConvert, 0x010E, 0x03CC, 18)]
+    // [InlineData(TestImages.Heif.Orange4x4, 0x010E, 0x001d, 21)]
     public void ReadFirstTile(string filename, int dataOffset, int dataSize, int tileOffset)
     {
         // Assign