Tweak grayscale converter code

src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.GrayScaleScalar.cs

@@ -41,11 +41,11 @@ internal abstract partial class JpegColorConverterBase
             float scale = 1F / maxValue;
             for (nuint i = 0; i < (nuint)values.Component0.Length; i++)
             {
-                ref float c0 = ref Unsafe.Add(ref c0Base, i);
+                float c = Unsafe.Add(ref c0Base, i) * scale;
-                c0 *= scale;
 
-                Unsafe.Add(ref c1Base, i) = c0;
+                Unsafe.Add(ref c0Base, i) = c;
-                Unsafe.Add(ref c2Base, i) = c0;
+                Unsafe.Add(ref c1Base, i) = c;
+                Unsafe.Add(ref c2Base, i) = c;
             }
         }
 

src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.GrayScaleVector128.cs

@@ -40,11 +40,11 @@ internal abstract partial class JpegColorConverterBase
             nuint n = values.Component0.Vector128Count<float>();
             for (nuint i = 0; i < n; i++)
             {
-                ref Vector128<float> c0 = ref Unsafe.Add(ref c0Base, i);
+                Vector128<float> c = Unsafe.Add(ref c0Base, i) * scale;
-                c0 *= scale;
 
-                Unsafe.Add(ref c1Base, i) = c0;
+                Unsafe.Add(ref c0Base, i) = c;
-                Unsafe.Add(ref c2Base, i) = c0;
+                Unsafe.Add(ref c1Base, i) = c;
+                Unsafe.Add(ref c2Base, i) = c;
             }
         }
 

src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.GrayScaleVector256.cs

@@ -36,11 +36,11 @@ internal abstract partial class JpegColorConverterBase
             nuint n = values.Component0.Vector256Count<float>();
             for (nuint i = 0; i < n; i++)
             {
-                ref Vector256<float> c0 = ref Unsafe.Add(ref c0Base, i);
+                Vector256<float> c = Unsafe.Add(ref c0Base, i) * scale;
-                c0 *= scale;
 
-                Unsafe.Add(ref c1Base, i) = c0;
+                Unsafe.Add(ref c0Base, i) = c;
-                Unsafe.Add(ref c2Base, i) = c0;
+                Unsafe.Add(ref c1Base, i) = c;
+                Unsafe.Add(ref c2Base, i) = c;
             }
         }
 

src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.GrayScaleVector512.cs

@@ -40,11 +40,11 @@ internal abstract partial class JpegColorConverterBase
             nuint n = values.Component0.Vector512Count<float>();
             for (nuint i = 0; i < n; i++)
             {
-                ref Vector512<float> c0 = ref Unsafe.Add(ref c0Base, i);
+                Vector512<float> c = Unsafe.Add(ref c0Base, i) * scale;
-                c0 *= scale;
 
-                Unsafe.Add(ref c1Base, i) = c0;
+                Unsafe.Add(ref c0Base, i) = c;
-                Unsafe.Add(ref c2Base, i) = c0;
+                Unsafe.Add(ref c1Base, i) = c;
+                Unsafe.Add(ref c2Base, i) = c;
             }
         }
 

src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.RgbScalar.cs

@@ -67,14 +67,9 @@ internal abstract partial class JpegColorConverterBase
 
             for (nuint i = 0; i < (nuint)values.Component0.Length; i++)
             {
-                ref float c0 = ref Unsafe.Add(ref c0Base, i);
+                Unsafe.Add(ref c0Base, i) *= scale;
-                c0 *= scale;
+                Unsafe.Add(ref c1Base, i) *= scale;
-
+                Unsafe.Add(ref c2Base, i) *= scale;
-                ref float c1 = ref Unsafe.Add(ref c1Base, i);
-                c1 *= scale;
-
-                ref float c2 = ref Unsafe.Add(ref c2Base, i);
-                c2 *= scale;
             }
         }