Merge pull request #1800 from SixLabors/bp/avoiddictionarys

Webp: Use byte arrays instead of Dictionary's for lookups

Author: brianpopow

src/ImageSharp/Formats/Webp/Lossy/LossyUtils.cs

@@ -934,11 +934,11 @@ private static void DoFilter2(Span<byte> p, int offset, int step)
             int p0 = p[offset - step];
             int q0 = p[offset];
             int q1 = p[offset + step];
-            int a = (3 * (q0 - p0)) + WebpLookupTables.Sclip1[p1 - q1];
-            int a1 = WebpLookupTables.Sclip2[(a + 4) >> 3];
-            int a2 = WebpLookupTables.Sclip2[(a + 3) >> 3];
-            p[offset - step] = WebpLookupTables.Clip1[p0 + a2];
-            p[offset] = WebpLookupTables.Clip1[q0 - a1];
+            int a = (3 * (q0 - p0)) + WebpLookupTables.Sclip1[p1 - q1 + 1020];
+            int a1 = WebpLookupTables.Sclip2[((a + 4) >> 3) + 112];
+            int a2 = WebpLookupTables.Sclip2[((a + 3) >> 3) + 112];
+            p[offset - step] = WebpLookupTables.Clip1[p0 + a2 + 255];
+            p[offset] = WebpLookupTables.Clip1[q0 - a1 + 255];
         }
 
         private static void DoFilter4(Span<byte> p, int offset, int step)
@@ -950,13 +950,13 @@ private static void DoFilter4(Span<byte> p, int offset, int step)
             int q0 = p[offset];
             int q1 = p[offset + step];
             int a = 3 * (q0 - p0);
-            int a1 = WebpLookupTables.Sclip2[(a + 4) >> 3];
-            int a2 = WebpLookupTables.Sclip2[(a + 3) >> 3];
+            int a1 = WebpLookupTables.Sclip2[((a + 4) >> 3) + 112];
+            int a2 = WebpLookupTables.Sclip2[((a + 3) >> 3) + 112];
             int a3 = (a1 + 1) >> 1;
-            p[offsetMinus2Step] = WebpLookupTables.Clip1[p1 + a3];
-            p[offset - step] = WebpLookupTables.Clip1[p0 + a2];
-            p[offset] = WebpLookupTables.Clip1[q0 - a1];
-            p[offset + step] = WebpLookupTables.Clip1[q1 - a3];
+            p[offsetMinus2Step] = WebpLookupTables.Clip1[p1 + a3 + 255];
+            p[offset - step] = WebpLookupTables.Clip1[p0 + a2 + 255];
+            p[offset] = WebpLookupTables.Clip1[q0 - a1 + 255];
+            p[offset + step] = WebpLookupTables.Clip1[q1 - a3 + 255];
         }
 
         private static void DoFilter6(Span<byte> p, int offset, int step)
@@ -971,18 +971,18 @@ private static void DoFilter6(Span<byte> p, int offset, int step)
             int q0 = p[offset];
             int q1 = p[offset + step];
             int q2 = p[offset + step2];
-            int a = WebpLookupTables.Sclip1[(3 * (q0 - p0)) + WebpLookupTables.Sclip1[p1 - q1]];
+            int a = WebpLookupTables.Sclip1[(3 * (q0 - p0)) + WebpLookupTables.Sclip1[p1 - q1 + 1020] + 1020];
 
             // a is in [-128,127], a1 in [-27,27], a2 in [-18,18] and a3 in [-9,9]
             int a1 = ((27 * a) + 63) >> 7;  // eq. to ((3 * a + 7) * 9) >> 7
             int a2 = ((18 * a) + 63) >> 7;  // eq. to ((2 * a + 7) * 9) >> 7
             int a3 = ((9 * a) + 63) >> 7;  // eq. to ((1 * a + 7) * 9) >> 7
-            p[offset - step3] = WebpLookupTables.Clip1[p2 + a3];
-            p[offset - step2] = WebpLookupTables.Clip1[p1 + a2];
-            p[offsetMinusStep] = WebpLookupTables.Clip1[p0 + a1];
-            p[offset] = WebpLookupTables.Clip1[q0 - a1];
-            p[offset + step] = WebpLookupTables.Clip1[q1 - a2];
-            p[offset + step2] = WebpLookupTables.Clip1[q2 - a3];
+            p[offset - step3] = WebpLookupTables.Clip1[p2 + a3 + 255];
+            p[offset - step2] = WebpLookupTables.Clip1[p1 + a2 + 255];
+            p[offsetMinusStep] = WebpLookupTables.Clip1[p0 + a1 + 255];
+            p[offset] = WebpLookupTables.Clip1[q0 - a1 + 255];
+            p[offset + step] = WebpLookupTables.Clip1[q1 - a2 + 255];
+            p[offset + step2] = WebpLookupTables.Clip1[q2 - a3 + 255];
         }
 
         [MethodImpl(InliningOptions.ShortMethod)]
@@ -992,7 +992,7 @@ private static bool NeedsFilter(Span<byte> p, int offset, int step, int t)
             int p0 = p[offset - step];
             int q0 = p[offset];
             int q1 = p[offset + step];
-            return (4 * WebpLookupTables.Abs0[p0 - q0]) + WebpLookupTables.Abs0[p1 - q1] <= t;
+            return (4 * WebpLookupTables.Abs0[p0 - q0 + 255]) + WebpLookupTables.Abs0[p1 - q1 + 255] <= t;
         }
 
         private static bool NeedsFilter2(Span<byte> p, int offset, int step, int t, int it)
@@ -1007,14 +1007,14 @@ private static bool NeedsFilter2(Span<byte> p, int offset, int step, int t, int
             int q1 = p[offset + step];
             int q2 = p[offset + step2];
             int q3 = p[offset + step3];
-            if ((4 * WebpLookupTables.Abs0[p0 - q0]) + WebpLookupTables.Abs0[p1 - q1] > t)
+            if ((4 * WebpLookupTables.Abs0[p0 - q0 + 255]) + WebpLookupTables.Abs0[p1 - q1 + 255] > t)
             {
                 return false;
             }
 
-            return WebpLookupTables.Abs0[p3 - p2] <= it && WebpLookupTables.Abs0[p2 - p1] <= it &&
-                   WebpLookupTables.Abs0[p1 - p0] <= it && WebpLookupTables.Abs0[q3 - q2] <= it &&
-                   WebpLookupTables.Abs0[q2 - q1] <= it && WebpLookupTables.Abs0[q1 - q0] <= it;
+            return WebpLookupTables.Abs0[p3 - p2 + 255] <= it && WebpLookupTables.Abs0[p2 - p1 + 255] <= it &&
+                   WebpLookupTables.Abs0[p1 - p0 + 255] <= it && WebpLookupTables.Abs0[q3 - q2 + 255] <= it &&
+                   WebpLookupTables.Abs0[q2 - q1 + 255] <= it && WebpLookupTables.Abs0[q1 - q0 + 255] <= it;
         }
 
         [MethodImpl(InliningOptions.ShortMethod)]
@@ -1024,7 +1024,7 @@ private static bool Hev(Span<byte> p, int offset, int step, int thresh)
             int p0 = p[offset - step];
             int q0 = p[offset];
             int q1 = p[offset + step];
-            return WebpLookupTables.Abs0[p1 - p0] > thresh || WebpLookupTables.Abs0[q1 - q0] > thresh;
+            return WebpLookupTables.Abs0[p1 - p0 + 255] > thresh || WebpLookupTables.Abs0[q1 - q0 + 255] > thresh;
         }
 
         [MethodImpl(InliningOptions.ShortMethod)]