diff --git a/src/ImageSharp/Formats/WebP/BitWriter/BitWriterBase.cs b/src/ImageSharp/Formats/WebP/BitWriter/BitWriterBase.cs
index fd3cd44d9d..1b011315c2 100644
--- a/src/ImageSharp/Formats/WebP/BitWriter/BitWriterBase.cs
+++ b/src/ImageSharp/Formats/WebP/BitWriter/BitWriterBase.cs
@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers.Binary;
+using System.IO;
 
 namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
 {
@@ -33,12 +35,32 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
             get { return this.buffer; }
         }
 
+        /// <summary>
+        /// Writes the encoded bytes of the image to the stream. Call Finish() before this.
+        /// </summary>
+        /// <param name="stream">The stream to write to.</param>
+        public void WriteToStream(Stream stream)
+        {
+            stream.Write(this.Buffer.AsSpan(0, this.NumBytes()));
+        }
+
         /// <summary>
         /// Resizes the buffer to write to.
         /// </summary>
         /// <param name="extraSize">The extra size in bytes needed.</param>
         public abstract void BitWriterResize(int extraSize);
 
+        /// <summary>
+        /// Returns the number of bytes of the encoded image data.
+        /// </summary>
+        /// <returns>The number of bytes of the image data.</returns>
+        public abstract int NumBytes();
+
+        /// <summary>
+        /// Flush leftover bits.
+        /// </summary>
+        public abstract void Finish();
+
         protected bool ResizeBuffer(int maxBytes, int sizeRequired)
         {
             if (maxBytes > 0 && sizeRequired < maxBytes)
@@ -60,5 +82,60 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
 
             return false;
         }
+
+        /// <summary>
+        /// Writes the encoded image to the stream.
+        /// </summary>
+        /// <param name="lossy">If true, lossy tag will be written, otherwise a lossless tag.</param>
+        /// <param name="stream">The stream to write to.</param>
+        public void WriteEncodedImageToStream(bool lossy, Stream stream)
+        {
+            this.Finish();
+            var numBytes = this.NumBytes();
+            var size = numBytes;
+            if (!lossy)
+            {
+                size++; // One byte extra for the VP8L signature.
+            }
+
+            var pad = size & 1;
+            var riffSize = WebPConstants.TagSize + WebPConstants.ChunkHeaderSize + size + pad;
+            this.WriteRiffHeader(riffSize, size, lossy, stream);
+            this.WriteToStream(stream);
+            if (pad == 1)
+            {
+                stream.WriteByte(0);
+            }
+        }
+
+        /// <summary>
+        /// Writes the RIFF header to the stream.
+        /// </summary>
+        /// <param name="riffSize">The block length.</param>
+        /// <param name="size">The size in bytes of the encoded image.</param>
+        /// <param name="lossy">If true, lossy tag will be written, otherwise a lossless tag.</param>
+        /// <param name="stream">The stream to write to.</param>
+        private void WriteRiffHeader(int riffSize, int size, bool lossy, Stream stream)
+        {
+            Span<byte> buffer = stackalloc byte[4];
+
+            stream.Write(WebPConstants.RiffFourCc);
+            BinaryPrimitives.WriteUInt32LittleEndian(buffer, (uint)riffSize);
+            stream.Write(buffer);
+            stream.Write(WebPConstants.WebPHeader);
+
+            if (lossy)
+            {
+                stream.Write(WebPConstants.Vp8MagicBytes);
+            }
+            else
+            {
+                stream.Write(WebPConstants.Vp8LMagicBytes);
+            }
+
+            BinaryPrimitives.WriteUInt32LittleEndian(buffer, (uint)size);
+            stream.Write(buffer);
+            stream.WriteByte(WebPConstants.Vp8LMagicByte);
+        }
     }
 }
diff --git a/src/ImageSharp/Formats/WebP/BitWriter/Vp8BitWriter.cs b/src/ImageSharp/Formats/WebP/BitWriter/Vp8BitWriter.cs
index 1150168eb7..8d3fe61b44 100644
--- a/src/ImageSharp/Formats/WebP/BitWriter/Vp8BitWriter.cs
+++ b/src/ImageSharp/Formats/WebP/BitWriter/Vp8BitWriter.cs
@@ -47,9 +47,10 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
             // this.error = false;
         }
 
-        public uint Pos
+        /// <inheritdoc/>
+        public override int NumBytes()
         {
-            get { return this.pos; }
+            return (int)this.pos;
         }
 
         public int PutCoeffs(int ctx, Vp8Residual residual)
@@ -179,7 +180,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
             this.ResizeBuffer(this.maxPos, (int)neededSize);
         }
 
-        public void Finish()
+        /// <inheritdoc/>
+        public override void Finish()
         {
            this.PutBits(0, 9 - this.nbBits);
            this.nbBits = 0;   // pad with zeroes.
diff --git a/src/ImageSharp/Formats/WebP/BitWriter/Vp8LBitWriter.cs b/src/ImageSharp/Formats/WebP/BitWriter/Vp8LBitWriter.cs
index 99c819f173..917646bfea 100644
--- a/src/ImageSharp/Formats/WebP/BitWriter/Vp8LBitWriter.cs
+++ b/src/ImageSharp/Formats/WebP/BitWriter/Vp8LBitWriter.cs
@@ -3,7 +3,6 @@
 
 using System;
 using System.Buffers.Binary;
-using System.IO;
 using SixLabors.ImageSharp.Formats.WebP.Lossless;
 
 namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
@@ -100,7 +99,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
             this.PutBits((uint)((bits << depth) | symbol), depth + nBits);
         }
 
-        public int NumBytes()
+        /// <inheritdoc/>
+        public override int NumBytes()
         {
             return this.cur + ((this.used + 7) >> 3);
         }
@@ -112,19 +112,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.BitWriter
             return new Vp8LBitWriter(clonedBuffer, this.bits, this.used, this.cur);
         }
 
-        /// <summary>
-        /// Writes the encoded bytes of the image to the stream. Call BitWriterFinish() before this.
-        /// </summary>
-        /// <param name="stream">The stream to write to.</param>
-        public void WriteToStream(Stream stream)
-        {
-            stream.Write(this.Buffer.AsSpan(0, this.NumBytes()));
-        }
-
-        /// <summary>
-        /// Flush leftover bits.
-        /// </summary>
-        public void BitWriterFinish()
+        /// <inheritdoc/>
+        public override void Finish()
         {
             this.BitWriterResize((this.used + 7) >> 3);
             while (this.used > 0)
diff --git a/src/ImageSharp/Formats/WebP/Lossless/Vp8LEncoder.cs b/src/ImageSharp/Formats/WebP/Lossless/Vp8LEncoder.cs
index e951c70e73..55e129e7dc 100644
--- a/src/ImageSharp/Formats/WebP/Lossless/Vp8LEncoder.cs
+++ b/src/ImageSharp/Formats/WebP/Lossless/Vp8LEncoder.cs
@@ -186,17 +186,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossless
             this.EncodeStream(image);
 
             // Write bytes from the bitwriter buffer to the stream.
-            this.bitWriter.BitWriterFinish();
-            var numBytes = this.bitWriter.NumBytes();
-            var vp8LSize = 1 + numBytes; // One byte extra for the VP8L signature.
-            var pad = vp8LSize & 1;
-            var riffSize = WebPConstants.TagSize + WebPConstants.ChunkHeaderSize + vp8LSize + pad;
-            this.WriteRiffHeader(riffSize, vp8LSize, stream);
-            this.bitWriter.WriteToStream(stream);
-            if (pad == 1)
-            {
-                stream.WriteByte(0);
-            }
+            this.bitWriter.WriteEncodedImageToStream(lossy: false, stream);
         }
 
         /// <summary>
@@ -226,26 +216,6 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossless
             this.bitWriter.PutBits(WebPConstants.Vp8LVersion, WebPConstants.Vp8LVersionBits);
         }
 
-        /// <summary>
-        /// Writes the RIFF header to the stream.
-        /// </summary>
-        /// <param name="riffSize">The block length.</param>
-        /// <param name="vp8LSize">The size in bytes of the compressed image.</param>
-        /// <param name="stream">The stream to write to.</param>
-        private void WriteRiffHeader(int riffSize, int vp8LSize, Stream stream)
-        {
-            Span<byte> buffer = stackalloc byte[4];
-
-            stream.Write(WebPConstants.RiffFourCc);
-            BinaryPrimitives.WriteUInt32LittleEndian(buffer, (uint)riffSize);
-            stream.Write(buffer);
-            stream.Write(WebPConstants.WebPHeader);
-            stream.Write(WebPConstants.Vp8LTag);
-            BinaryPrimitives.WriteUInt32LittleEndian(buffer, (uint)vp8LSize);
-            stream.Write(buffer);
-            stream.WriteByte(WebPConstants.Vp8LMagicByte);
-        }
-
         /// <summary>
         /// Encodes the image stream using lossless webp format.
         /// </summary>
diff --git a/src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs b/src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs
index 5ec73669d4..9901d0cff0 100644
--- a/src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs
+++ b/src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs
@@ -376,7 +376,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             else
             {
                 this.ImportLine(y.Slice(yStartIdx - yStride), 1, yTop, w, 16);
-                this.ImportLine(u.Slice(uvStartIdx - uvStride), 1, this.UvTop.GetSpan(), uvw, 8);
+                this.ImportLine(u.Slice(uvStartIdx - uvStride), 1, this.UvTop.GetSpan().Slice(8), uvw, 8);
                 this.ImportLine(v.Slice(uvStartIdx - uvStride), 1, this.UvTop.GetSpan().Slice(8), uvw, 8);
             }
         }
@@ -502,8 +502,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             int predIdx = this.predIdx;
             int x = this.I4 & 3;
             int y = this.I4 >> 2;
-            int left = (x == 0) ? this.Preds.Slice(predIdx)[(y * predsWidth) - 1] : modes[this.I4 - 1];
-            int top = (y == 0) ? this.Preds.Slice(predIdx)[-predsWidth + x] : modes[this.I4 - 4];
+            int left = (x == 0) ? this.Preds.Slice(predIdx + (y * predsWidth) - 1)[0] : modes[this.I4 - 1];
+            int top = (y == 0) ? this.Preds.Slice(predIdx - predsWidth + x)[0] : modes[this.I4 - 4];
             return WebPLookupTables.Vp8FixedCostsI4[top, left];
         }
 
@@ -590,13 +590,14 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
         public bool RotateI4(Span<byte> yuvOut)
         {
             Span<byte> blk = yuvOut.Slice(WebPLookupTables.Vp8Scan[this.I4]);
-            Span<byte> top = this.I4Boundary.AsSpan(this.I4BoundaryIdx);
+            Span<byte> top = this.I4Boundary.AsSpan();
+            int topOffset = this.I4BoundaryIdx;
             int i;
 
             // Update the cache with 7 fresh samples.
             for (i = 0; i <= 3; ++i)
             {
-                top[-4 + i] = blk[i + (3 * WebPConstants.Bps)];   // Store future top samples.
+                top[topOffset - 4 + i] = blk[i + (3 * WebPConstants.Bps)];   // Store future top samples.
             }
 
             if ((this.I4 & 3) != 3)
@@ -605,7 +606,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 for (i = 0; i <= 2; ++i)
                 {
                     // store future left samples
-                    top[i] = blk[3 + ((2 - i) * WebPConstants.Bps)];
+                    top[topOffset + i] = blk[3 + ((2 - i) * WebPConstants.Bps)];
                 }
             }
             else
@@ -613,7 +614,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 // else replicate top-right samples, as says the specs.
                 for (i = 0; i <= 3; ++i)
                 {
-                    top[i] = top[i + 4];
+                    top[topOffset + i] = top[topOffset + i + 4];
                 }
             }
 
@@ -660,7 +661,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
 
         public void MakeIntra4Preds()
         {
-            this.EncPredLuma4(this.YuvP, this.I4Boundary.AsSpan(this.I4BoundaryIdx));
+            this.EncPredLuma4(this.YuvP, this.I4Boundary, this.I4BoundaryIdx);
         }
 
         public void SwapOut()
@@ -788,18 +789,18 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
 
         // Left samples are top[-5 .. -2], top_left is top[-1], top are
         // located at top[0..3], and top right is top[4..7]
-        private void EncPredLuma4(Span<byte> dst, Span<byte> top)
+        private void EncPredLuma4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            this.Dc4(dst.Slice(I4DC4), top);
-            this.Tm4(dst.Slice(I4TM4), top);
-            this.Ve4(dst.Slice(I4VE4), top);
-            this.He4(dst.Slice(I4HE4), top);
-            this.Rd4(dst.Slice(I4RD4), top);
-            this.Vr4(dst.Slice(I4VR4), top);
+            this.Dc4(dst, top, topOffset);
+            this.Tm4(dst.Slice(I4TM4), top, topOffset);
+            this.Ve4(dst.Slice(I4VE4), top, topOffset);
+            this.He4(dst.Slice(I4HE4), top, topOffset);
+            this.Rd4(dst.Slice(I4RD4), top, topOffset);
+            this.Vr4(dst.Slice(I4VR4), top, topOffset);
             this.Ld4(dst.Slice(I4LD4), top);
             this.Vl4(dst.Slice(I4VL4), top);
-            this.Hd4(dst.Slice(I4HD4), top);
-            this.Hu4(dst.Slice(I4HU4), top);
+            this.Hd4(dst.Slice(I4HD4), top, topOffset);
+            this.Hu4(dst.Slice(I4HU4), top, topOffset);
         }
 
         private void DcMode(Span<byte> dst, Span<byte> left, Span<byte> top, int size, int round, int shift)
@@ -922,42 +923,42 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             }
         }
 
-        private void Dc4(Span<byte> dst, Span<byte> top)
+        private void Dc4(Span<byte> dst, Span<byte> top, int topOffset)
         {
             uint dc = 4;
             int i;
             for (i = 0; i < 4; ++i)
             {
-                dc += (uint)(top[i] + top[-5 + i]);
+                dc += (uint)(top[topOffset + i] + top[topOffset - 5 + i]);
             }
 
             this.Fill(dst, (int)(dc >> 3), 4);
         }
 
-        private void Tm4(Span<byte> dst, Span<byte> top)
+        private void Tm4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            Span<byte> clip = this.clip1.AsSpan(255 - top[-1]);
+            Span<byte> clip = this.clip1.AsSpan(255 - top[topOffset - 1]);
             for (int y = 0; y < 4; ++y)
             {
-                Span<byte> clipTable = clip.Slice(top[-2 - y]);
+                Span<byte> clipTable = clip.Slice(top[topOffset - 2 - y]);
                 for (int x = 0; x < 4; ++x)
                 {
-                    dst[x] = clipTable[top[x]];
+                    dst[x] = clipTable[top[topOffset + x]];
                 }
 
                 dst = dst.Slice(WebPConstants.Bps);
             }
         }
 
-        private void Ve4(Span<byte> dst, Span<byte> top)
+        private void Ve4(Span<byte> dst, Span<byte> top, int topOffset)
         {
             // vertical
             byte[] vals =
             {
-                LossyUtils.Avg3(top[-1], top[0], top[1]),
-                LossyUtils.Avg3(top[0], top[1], top[2]),
-                LossyUtils.Avg3(top[1], top[2], top[3]),
-                LossyUtils.Avg3(top[2], top[3], top[4])
+                LossyUtils.Avg3(top[topOffset - 1], top[topOffset], top[topOffset + 1]),
+                LossyUtils.Avg3(top[topOffset], top[topOffset + 1], top[topOffset + 2]),
+                LossyUtils.Avg3(top[topOffset + 1], top[topOffset + 2], top[topOffset + 3]),
+                LossyUtils.Avg3(top[topOffset + 2], top[topOffset + 3], top[topOffset + 4])
             };
 
             for (int i = 0; i < 4; ++i)
@@ -966,14 +967,14 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             }
         }
 
-        private void He4(Span<byte> dst, Span<byte> top)
+        private void He4(Span<byte> dst, Span<byte> top, int topOffset)
         {
             // horizontal
-            byte x = top[-1];
-            byte i = top[-2];
-            byte j = top[-3];
-            byte k = top[-4];
-            byte l = top[-5];
+            byte x = top[topOffset - 1];
+            byte i = top[topOffset - 2];
+            byte j = top[topOffset - 3];
+            byte k = top[topOffset - 4];
+            byte l = top[topOffset - 5];
 
             uint val = 0x01010101U * LossyUtils.Avg3(x, i, j);
             BinaryPrimitives.WriteUInt32BigEndian(dst, val);
@@ -985,17 +986,17 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             BinaryPrimitives.WriteUInt32BigEndian(dst.Slice(1 * WebPConstants.Bps), val);
         }
 
-        private void Rd4(Span<byte> dst, Span<byte> top)
+        private void Rd4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            byte x = top[-1];
-            byte i = top[-2];
-            byte j = top[-3];
-            byte k = top[-4];
-            byte l = top[-5];
-            byte a = top[0];
-            byte b = top[1];
-            byte c = top[2];
-            byte d = top[3];
+            byte x = top[topOffset - 1];
+            byte i = top[topOffset - 2];
+            byte j = top[topOffset - 3];
+            byte k = top[topOffset - 4];
+            byte l = top[topOffset - 5];
+            byte a = top[topOffset];
+            byte b = top[topOffset + 1];
+            byte c = top[topOffset + 2];
+            byte d = top[topOffset + 3];
 
             LossyUtils.Dst(dst, 0, 3, LossyUtils.Avg3(j, k, l));
             var ijk = LossyUtils.Avg3(i, j, k);
@@ -1020,16 +1021,16 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             LossyUtils.Dst(dst, 3, 0, LossyUtils.Avg3(d, c, b));
         }
 
-        private void Vr4(Span<byte> dst, Span<byte> top)
+        private void Vr4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            byte x = top[-1];
-            byte i = top[-2];
-            byte j = top[-3];
-            byte k = top[-4];
-            byte a = top[0];
-            byte b = top[1];
-            byte c = top[2];
-            byte d = top[3];
+            byte x = top[topOffset - 1];
+            byte i = top[topOffset - 2];
+            byte j = top[topOffset - 3];
+            byte k = top[topOffset - 4];
+            byte a = top[topOffset];
+            byte b = top[topOffset + 1];
+            byte c = top[topOffset + 2];
+            byte d = top[topOffset + 3];
 
             var xa = LossyUtils.Avg2(x, a);
             LossyUtils.Dst(dst, 0, 0, xa);
@@ -1124,16 +1125,16 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             LossyUtils.Dst(dst, 3, 3, LossyUtils.Avg3(f, g, h));
         }
 
-        private void Hd4(Span<byte> dst, Span<byte> top)
+        private void Hd4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            byte x = top[-1];
-            byte i = top[-2];
-            byte j = top[-3];
-            byte k = top[-4];
-            byte l = top[-5];
-            byte a = top[0];
-            byte b = top[1];
-            byte c = top[2];
+            byte x = top[topOffset - 1];
+            byte i = top[topOffset - 2];
+            byte j = top[topOffset - 3];
+            byte k = top[topOffset - 4];
+            byte l = top[topOffset - 5];
+            byte a = top[topOffset];
+            byte b = top[topOffset + 1];
+            byte c = top[topOffset + 2];
 
             var ix = LossyUtils.Avg2(i, x);
             LossyUtils.Dst(dst, 0, 0, ix);
@@ -1159,12 +1160,12 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             LossyUtils.Dst(dst, 1, 3, LossyUtils.Avg3(l, k, j));
         }
 
-        private void Hu4(Span<byte> dst, Span<byte> top)
+        private void Hu4(Span<byte> dst, Span<byte> top, int topOffset)
         {
-            byte i = top[-2];
-            byte j = top[-3];
-            byte k = top[-4];
-            byte l = top[-5];
+            byte i = top[topOffset - 2];
+            byte j = top[topOffset - 3];
+            byte k = top[topOffset - 4];
+            byte l = top[topOffset - 5];
 
             LossyUtils.Dst(dst, 0, 0, LossyUtils.Avg2(i, j));
             var jk = LossyUtils.Avg2(j, k);
@@ -1285,6 +1286,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
         {
             int topSize = this.mbw * 16;
             this.YTop.Slice(0, topSize).Fill(127);
+            this.UvTop.GetSpan().Fill(127);
             this.Nz.GetSpan().Fill(0);
         }
 
diff --git a/src/ImageSharp/Formats/WebP/Lossy/Vp8Encoder.cs b/src/ImageSharp/Formats/WebP/Lossy/Vp8Encoder.cs
index c9426af16b..c224a58af3 100644
--- a/src/ImageSharp/Formats/WebP/Lossy/Vp8Encoder.cs
+++ b/src/ImageSharp/Formats/WebP/Lossy/Vp8Encoder.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Buffers;
+using System.Buffers.Binary;
 using System.IO;
 using System.Runtime.CompilerServices;
 
@@ -250,7 +251,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
             }
             while (it.Next());
 
-            this.bitWriter.Finish();
+            // Write bytes from the bitwriter buffer to the stream.
+            this.bitWriter.WriteEncodedImageToStream(lossy: true, stream);
         }
 
         /// <inheritdoc/>
@@ -708,7 +710,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
 
             it.NzToBytes();
 
-            var pos1 = this.bitWriter.Pos;
+            int pos1 = this.bitWriter.NumBytes();
             if (i16)
             {
                 residual.Init(0, 1, this.proba);
@@ -734,7 +736,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 }
             }
 
-            var pos2 = this.bitWriter.Pos;
+            int pos2 = this.bitWriter.NumBytes();
 
             // U/V
             residual.Init(0, 2, this.proba);
@@ -752,7 +754,7 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 }
             }
 
-            var pos3 = this.bitWriter.Pos;
+            int pos3 = this.bitWriter.NumBytes();
             it.LumaBits = pos2 - pos1;
             it.UvBits = pos3 - pos2;
             it.BitCount[segment, i16 ? 1 : 0] += it.LumaBits;
@@ -942,8 +944,8 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 uint coeff = (uint)((sign ? -input[j] : input[j]) + mtx.Sharpen[j]);
                 if (coeff > mtx.ZThresh[j])
                 {
-                    uint q = (uint)mtx.Q[j];
-                    uint iQ = (uint)mtx.IQ[j];
+                    uint q = mtx.Q[j];
+                    uint iQ = mtx.IQ[j];
                     uint b = mtx.Bias[j];
                     int level = this.QuantDiv(coeff, iQ, b);
                     if (level > MaxLevel)
@@ -1342,16 +1344,18 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
         private int GetSse(Span<byte> a, Span<byte> b, int w, int h)
         {
             int count = 0;
+            int aOffset = 0;
+            int bOffset = 0;
             for (int y = 0; y < h; ++y)
             {
                 for (int x = 0; x < w; ++x)
                 {
-                    int diff = a[x] - b[x];
+                    int diff = a[aOffset + x] - b[bOffset + x];
                     count += diff * diff;
                 }
 
-                a = a.Slice(WebPConstants.Bps);
-                b = b.Slice(WebPConstants.Bps);
+                aOffset += WebPConstants.Bps;
+                bOffset += WebPConstants.Bps;
             }
 
             return count;
diff --git a/src/ImageSharp/Formats/WebP/Lossy/Vp8Matrix.cs b/src/ImageSharp/Formats/WebP/Lossy/Vp8Matrix.cs
index 9c7711352e..8095478df3 100644
--- a/src/ImageSharp/Formats/WebP/Lossy/Vp8Matrix.cs
+++ b/src/ImageSharp/Formats/WebP/Lossy/Vp8Matrix.cs
@@ -74,10 +74,10 @@ namespace SixLabors.ImageSharp.Formats.WebP.Lossy
                 this.IQ[i] = (ushort)((1 << WebPConstants.QFix) / this.Q[i]);
                 this.Bias[i] = (uint)this.BIAS(bias);
 
-                // zthresh_ is the exact value such that QUANTDIV(coeff, iQ, B) is:
+                // zthresh is the exact value such that QUANTDIV(coeff, iQ, B) is:
                 //   * zero if coeff <= zthresh
                 //   * non-zero if coeff > zthresh
-                this.ZThresh[i] = (uint)(((1 << WebPConstants.QFix) - 1 - this.Bias[i]) / this.IQ[i]);
+                this.ZThresh[i] = ((1 << WebPConstants.QFix) - 1 - this.Bias[i]) / this.IQ[i];
             }
 
             for (i = 2; i < 16; ++i)
diff --git a/src/ImageSharp/Formats/WebP/WebPConstants.cs b/src/ImageSharp/Formats/WebP/WebPConstants.cs
index 6721b2da12..a53130e2a8 100644
--- a/src/ImageSharp/Formats/WebP/WebPConstants.cs
+++ b/src/ImageSharp/Formats/WebP/WebPConstants.cs
@@ -38,7 +38,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Header bytes identifying a lossless image.
         /// </summary>
-        public static readonly byte[] Vp8LTag =
+        public static readonly byte[] Vp8LMagicBytes =
         {
             0x56, // V
             0x50, // P