Inline AV1 inverse transform clamping

src/ImageSharp/Formats/Heif/Av1/Transform/Av1Inverse2dTransformer.cs

@@ -542,6 +542,8 @@ internal static class Av1Inverse2dTransformer
         int shift0 = config.Shift0;
         int shift1 = config.Shift1;
         bool normalizeRectangle = Math.Abs(config.TransformSize.GetRectangleLogRatio()) == 1;
+        byte rowClampBits = (byte)(bitDepth + 8);
+        byte columnClampBits = (byte)Math.Max(bitDepth + 6, 16);
         Span<int> tempIn = workspace[..vectorLength];
         Span<int> tempOut = workspace.Slice(vectorLength, vectorLength);
         Span<int> step = workspace.Slice(2 * vectorLength, vectorLength);
@@ -554,12 +556,12 @@ internal static class Av1Inverse2dTransformer
             for (int column = 0; column < width; column++)
             {
                 int value = input[rowOffset + column];
-                tempIn[column] = normalizeRectangle
+                value = normalizeRectangle
                     ? Av1Math.RoundShift((long)value * Av1InverseTransformMath.NewInverseSqrt2, Av1InverseTransformMath.NewSqrt2BitCount)
                     : value;
+                tempIn[column] = Av1Transform1dMath.Clamp(value, rowClampBits);
             }
 
-            Av1InverseTransformMath.ClampBuffer(tempIn, width, (byte)(bitDepth + 8));
             TRowOperator.Transform(tempIn, tempOut, step, config.CosBitRow, config.StageRangeRow);
             Av1InverseTransformMath.RoundShiftArray(tempOut, width, -shift0);
             tempOut[..width].CopyTo(buffer.Slice(rowOffset, width));
@@ -571,10 +573,9 @@ internal static class Av1Inverse2dTransformer
 
             for (int row = 0; row < height; row++)
             {
-                tempIn[row] = buffer[(row * width) + sourceColumn];
+                tempIn[row] = Av1Transform1dMath.Clamp(buffer[(row * width) + sourceColumn], columnClampBits);
             }
 
-            Av1InverseTransformMath.ClampBuffer(tempIn, height, (byte)Math.Max(bitDepth + 6, 16));
             TColumnOperator.Transform(tempIn, tempOut, step, config.CosBitColumn, config.StageRangeColumn);
             Av1InverseTransformMath.RoundShiftArray(tempOut, height, -shift1);
 

src/ImageSharp/Formats/Heif/Av1/Transform/Av1InverseTransformMath.cs

@@ -261,38 +261,6 @@ internal static class Av1InverseTransformMath
         }
     }
 
-    /// <summary>
-    /// Clamps a transform-stage buffer to a signed range of the specified bit width.
-    /// </summary>
-    /// <param name="buffer">The transform-stage values.</param>
-    /// <param name="size">The number of values to clamp.</param>
-    /// <param name="bit">The signed range width in bits.</param>
-    internal static void ClampBuffer(Span<int> buffer, int size, byte bit)
-    {
-        for (int i = 0; i < size; i++)
-        {
-            buffer[i] = ClampValue(buffer[i], bit);
-        }
-    }
-
-    /// <summary>
-    /// Clamps one transform-stage value to a signed range of the specified bit width.
-    /// </summary>
-    /// <param name="value">The value to clamp.</param>
-    /// <param name="bit">The signed range width in bits.</param>
-    /// <returns>The clamped value.</returns>
-    private static int ClampValue(int value, byte bit)
-    {
-        if (bit <= 0)
-        {
-            return value; // Do nothing for invalid clamp bit.
-        }
-
-        long maximum = (1L << (bit - 1)) - 1;
-        long minimum = -(1L << (bit - 1));
-        return (int)Av1Math.Clamp(value, minimum, maximum);
-    }
-
     /// <summary>
     /// Restricts an inverse-transform residual to the intermediate range permitted for the sample bit depth.
     /// </summary>