Simplify jpeg encoder and fix for Windows ARM

Directory.Build.props

@@ -30,17 +30,17 @@
 
   <!--
     https://apisof.net/
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========+
-    | SUPPORTS          | MATHF | HASHCODE | EXTENDED_INTRINSICS | SPAN_STREAM | ENCODING_STRING | RUNTIME_INTRINSICS | CODECOVERAGE | HOTPATH |
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|
-    | netcoreapp3.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        Y           |      Y       |    Y    |
-    | netcoreapp2.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        N           |      Y       |    N    |
-    | netcoreapp2.0     |   Y   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |
-    | netstandard2.1    |   Y   |    Y     |         N           |      Y      |        Y        |        N           |      Y       |    N    |
-    | netstandard2.0    |   N   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |
-    | netstandard1.3    |   N   |    N     |         N           |      N      |        N        |        N           |      N       |    N    |
-    | net472            |   N   |    N     |         Y           |      N      |        N        |        N           |      Y       |    N    |
-    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========+============|
+    | SUPPORTS          | MATHF | HASHCODE | EXTENDED_INTRINSICS | SPAN_STREAM | ENCODING_STRING | RUNTIME_INTRINSICS | CODECOVERAGE | HOTPATH | CREATESPAN |
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|============|
+    | netcoreapp3.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        Y           |      Y       |    Y    |      Y     |
+    | netcoreapp2.1     |   Y   |    Y     |         Y           |      Y      |        Y        |        N           |      Y       |    N    |      Y     |
+    | netcoreapp2.0     |   Y   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |      Y     |
+    | netstandard2.1    |   Y   |    Y     |         N           |      Y      |        Y        |        N           |      Y       |    N    |      Y     |
+    | netstandard2.0    |   N   |    N     |         N           |      N      |        N        |        N           |      Y       |    N    |      N     |
+    | netstandard1.3    |   N   |    N     |         N           |      N      |        N        |        N           |      N       |    N    |      N     |
+    | net472            |   N   |    N     |         Y           |      N      |        N        |        N           |      Y       |    N    |      N     |
+    +===================+=======+==========+=====================+=============+=================+====================+==============+=========|============|
     -->
 
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
@@ -52,6 +52,7 @@
     <DefineConstants>$(DefineConstants);SUPPORTS_RUNTIME_INTRINSICS</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_HOTPATH</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.1'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
@@ -60,17 +61,20 @@
     <DefineConstants>$(DefineConstants);SUPPORTS_SPAN_STREAM</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_ENCODING_STRING</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.0'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.1'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MATHF</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_HASHCODE</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_SPAN_STREAM</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_ENCODING_STRING</DefineConstants>
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_CREATESPAN</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
     <DefineConstants>$(DefineConstants);SUPPORTS_CODECOVERAGE</DefineConstants>

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.cs

@@ -376,45 +376,40 @@ public static unsafe void DequantizeBlock(Block8x8F* blockPtr, Block8x8F* qtPtr,
         /// <param name="block">Source block</param>
         /// <param name="dest">Destination block</param>
         /// <param name="qt">The quantization table</param>
-        /// <param name="unzigPtr">Pointer to elements of <see cref="ZigZag"/></param>
+        /// <param name="unZig">The 8x8 Unzig block.</param>
         public static unsafe void Quantize(
-            Block8x8F* block,
-            Block8x8F* dest,
-            Block8x8F* qt,
-            byte* unzigPtr)
+            ref Block8x8F block,
+            ref Block8x8F dest,
+            ref Block8x8F qt,
+            ref ZigZag unZig)
         {
-            float* s = (float*)block;
-            float* d = (float*)dest;
-
             for (int zig = 0; zig < Size; zig++)
             {
-                d[zig] = s[unzigPtr[zig]];
+                dest[zig] = block[unZig[zig]];
             }
 
-            DivideRoundAll(ref *dest, ref *qt);
+            DivideRoundAll(ref dest, ref qt);
         }
 
         /// <summary>
         /// Scales the 16x16 region represented by the 4 source blocks to the 8x8 DST block.
         /// </summary>
         /// <param name="destination">The destination block.</param>
         /// <param name="source">The source block.</param>
-        public static unsafe void Scale16X16To8X8(Block8x8F* destination, Block8x8F* source)
+        public static unsafe void Scale16X16To8X8(ref Block8x8F destination, ReadOnlySpan<Block8x8F> source)
         {
-            float* d = (float*)destination;
             for (int i = 0; i < 4; i++)
             {
                 int dstOff = ((i & 2) << 4) | ((i & 1) << 2);
-
-                float* iSource = (float*)(source + i);
+                Block8x8F iSource = source[i];
 
                 for (int y = 0; y < 4; y++)
                 {
                     for (int x = 0; x < 4; x++)
                     {
                         int j = (16 * y) + (2 * x);
                         float sum = iSource[j] + iSource[j + 1] + iSource[j + 8] + iSource[j + 9];
-                        d[(8 * y) + x + dstOff] = (sum + 2) / 4;
+                        destination[(8 * y) + x + dstOff] = (sum + 2) * .25F;
                     }
                 }
             }
@@ -589,7 +584,7 @@ private static Vector<float> NormalizeAndRound(Vector<float> row, Vector<float>
         private static Vector4 DivideRound(Vector4 dividend, Vector4 divisor)
         {
             // sign(dividend) = max(min(dividend, 1), -1)
-            var sign = Vector4Utilities.FastClamp(dividend, NegativeOne, Vector4.One);
+            Vector4 sign = Vector4Utilities.FastClamp(dividend, NegativeOne, Vector4.One);
 
             // AlmostRound(dividend/divisor) = dividend/divisor + 0.5*sign(dividend)
             return (dividend / divisor) + (sign * Offset);

src/ImageSharp/Formats/Jpeg/Components/Encoder/RgbToYCbCrTables.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 using System.Runtime.CompilerServices;
@@ -96,30 +96,27 @@ public static RgbToYCbCrTables Create()
         /// Optimized method to allocates the correct y, cb, and cr values to the DCT blocks from the given r, g, b values.
         /// </summary>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void ConvertPixelInto(int r, int g, int b, ref float yResult, ref float cbResult, ref float crResult)
+        public void ConvertPixelInto(
+            int r,
+            int g,
+            int b,
+            ref Block8x8F yResult,
+            ref Block8x8F cbResult,
+            ref Block8x8F crResult,
+            int i)
         {
-            ref int start = ref Unsafe.As<RgbToYCbCrTables, int>(ref this);
+            // float y = (0.299F * r) + (0.587F * g) + (0.114F * b);
+            yResult[i] = (this.YRTable[r] + this.YGTable[g] + this.YBTable[b]) >> ScaleBits;
 
-            ref int yR = ref start;
-            ref int yG = ref Unsafe.Add(ref start, 256 * 1);
-            ref int yB = ref Unsafe.Add(ref start, 256 * 2);
+            // float cb = 128F + ((-0.168736F * r) - (0.331264F * g) + (0.5F * b));
+            cbResult[i] = (this.CbRTable[r] + this.CbGTable[g] + this.CbBTable[b]) >> ScaleBits;
 
-            ref int cbR = ref Unsafe.Add(ref start, 256 * 3);
-            ref int cbG = ref Unsafe.Add(ref start, 256 * 4);
-            ref int cbB = ref Unsafe.Add(ref start, 256 * 5);
-
-            ref int crG = ref Unsafe.Add(ref start, 256 * 6);
-            ref int crB = ref Unsafe.Add(ref start, 256 * 7);
-
-            yResult = (Unsafe.Add(ref yR, r) + Unsafe.Add(ref yG, g) + Unsafe.Add(ref yB, b)) >> ScaleBits;
-            cbResult = (Unsafe.Add(ref cbR, r) + Unsafe.Add(ref cbG, g) + Unsafe.Add(ref cbB, b)) >> ScaleBits;
-            crResult = (Unsafe.Add(ref cbB, r) + Unsafe.Add(ref crG, g) + Unsafe.Add(ref crB, b)) >> ScaleBits;
+            // float cr = MathF.Round(y + (1.772F * cb), MidpointRounding.AwayFromZero);
+            crResult[i] = (this.CbBTable[r] + this.CrGTable[g] + this.CrBTable[b]) >> ScaleBits;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static int Fix(float x)
-        {
-            return (int)((x * (1L << ScaleBits)) + 0.5F);
-        }
+            => (int)((x * (1L << ScaleBits)) + 0.5F);
     }
-}
+}

src/ImageSharp/Formats/Jpeg/Components/Encoder/YCbCrForwardConverter{TPixel}.cs

@@ -62,9 +62,9 @@ public void Convert(ImageFrame<TPixel> frame, int x, int y, in RowOctet<TPixel>
             Span<Rgb24> rgbSpan = this.rgbBlock.AsSpanUnsafe();
             PixelOperations<TPixel>.Instance.ToRgb24(frame.GetConfiguration(), this.pixelBlock.AsSpanUnsafe(), rgbSpan);
 
-            ref float yBlockStart = ref Unsafe.As<Block8x8F, float>(ref this.Y);
-            ref float cbBlockStart = ref Unsafe.As<Block8x8F, float>(ref this.Cb);
-            ref float crBlockStart = ref Unsafe.As<Block8x8F, float>(ref this.Cr);
+            ref Block8x8F yBlock = ref this.Y;
+            ref Block8x8F cbBlock = ref this.Cb;
+            ref Block8x8F crBlock = ref this.Cr;
             ref Rgb24 rgbStart = ref rgbSpan[0];
 
             for (int i = 0; i < 64; i++)
@@ -75,9 +75,10 @@ public void Convert(ImageFrame<TPixel> frame, int x, int y, in RowOctet<TPixel>
                     c.R,
                     c.G,
                     c.B,
-                    ref Unsafe.Add(ref yBlockStart, i),
-                    ref Unsafe.Add(ref cbBlockStart, i),
-                    ref Unsafe.Add(ref crBlockStart, i));
+                    ref yBlock,
+                    ref cbBlock,
+                    ref crBlock,
+                    i);
             }
         }
     }

src/ImageSharp/Formats/Jpeg/Components/GenericBlock8x8.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -16,7 +15,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components
     /// </summary>
     [StructLayout(LayoutKind.Sequential)]
     internal unsafe partial struct GenericBlock8x8<T>
-        where T : struct
+        where T : unmanaged
     {
         public const int Size = 64;
 
@@ -110,6 +109,14 @@ public void LoadAndStretchEdges(Buffer2D<T> source, int sourceX, int sourceY, in
         /// <summary>
         /// Only for on-stack instances!
         /// </summary>
-        public Span<T> AsSpanUnsafe() => new Span<T>(Unsafe.AsPointer(ref this), Size);
+        public Span<T> AsSpanUnsafe()
+        {
+#if SUPPORTS_CREATESPAN
+            Span<GenericBlock8x8<T>> s = MemoryMarshal.CreateSpan(ref this, 1);
+            return MemoryMarshal.Cast<GenericBlock8x8<T>, T>(s);
+#else
+            return new Span<T>(Unsafe.AsPointer(ref this), Size);
+#endif
+        }
     }
 }