Fix issue in ImportBlock

src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs

@@ -768,10 +768,12 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
             int srcIdx = 0;
             for (int i = 0; i < h; ++i)
             {
+                // memcpy(dst, src, w);
                 src.Slice(srcIdx, w).CopyTo(dst.Slice(dstIdx));
                 if (w < size)
                 {
-                    dst.Slice(dstIdx, size - w).Fill(dst[dstIdx + w - 1]);
+                    // memset(dst + w, dst[w - 1], size - w);
+                    dst.Slice(dstIdx + w, size - w).Fill(dst[dstIdx + w - 1]);
                 }
 
                 dstIdx += WebpConstants.Bps;
@@ -780,7 +782,8 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
 
             for (int i = h; i < size; ++i)
             {
-                dst.Slice(dstIdx - WebpConstants.Bps, size).CopyTo(dst);
+                // memcpy(dst, dst - BPS, size);
+                dst.Slice(dstIdx - WebpConstants.Bps, size).CopyTo(dst.Slice(dstIdx));
                 dstIdx += WebpConstants.Bps;
             }
         }

src/ImageSharp/Formats/WebP/Lossy/Vp8Encoder.cs

@@ -609,7 +609,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
                 Vp8MacroBlockInfo mb = this.MbInfo[n];
                 int alpha = mb.Alpha;
                 mb.Segment = map[alpha];
-                mb.Alpha = centers[map[alpha]];  // for the record.
+                mb.Alpha = centers[map[alpha]];
             }
 
             // TODO: add possibility for SmoothSegmentMap
@@ -790,11 +790,11 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
                 m.Y2 = new Vp8Matrix();
                 m.Uv = new Vp8Matrix();
 
-                m.Y1.Q[0] = WebpLookupTables.DcTable[Numerics.Clamp(q, 0, 127)];
+                m.Y1.Q[0] = WebpLookupTables.DcTable[Numerics.Clamp(q + this.DqY1Dc, 0, 127)];
                 m.Y1.Q[1] = WebpLookupTables.AcTable[Numerics.Clamp(q, 0, 127)];
 
-                m.Y2.Q[0] = (ushort)(WebpLookupTables.DcTable[Numerics.Clamp(q, 0, 127)] * 2);
-                m.Y2.Q[1] = WebpLookupTables.AcTable2[Numerics.Clamp(q, 0, 127)];
+                m.Y2.Q[0] = (ushort)(WebpLookupTables.DcTable[Numerics.Clamp(q + this.DqY2Dc, 0, 127)] * 2);
+                m.Y2.Q[1] = WebpLookupTables.AcTable2[Numerics.Clamp(q + this.DqY2Ac, 0, 127)];
 
                 m.Uv.Q[0] = WebpLookupTables.DcTable[Numerics.Clamp(q + this.DqUvDc, 0, 117)];
                 m.Uv.Q[1] = WebpLookupTables.AcTable[Numerics.Clamp(q + this.DqUvAc, 0, 127)];
@@ -803,8 +803,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
                 int qi16 = m.Y2.Expand(1);
                 int quv = m.Uv.Expand(2);
 
-                m.I4Penalty = 1000 * qi4 * qi4;
-
                 m.LambdaI16 = 3 * qi16 * qi16;
                 m.LambdaI4 = (3 * qi4 * qi4) >> 7;
                 m.LambdaUv = (3 * quv * quv) >> 6;

src/ImageSharp/Formats/WebP/Lossy/Vp8Matrix.cs

@@ -106,9 +106,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
             return (sum + 8) >> 4;
         }
 
-        private int BIAS(int b)
-        {
-            return b << (WebpConstants.QFix - 8);
-        }
+        private int BIAS(int b) => b << (WebpConstants.QFix - 8);
     }
 }