Remove not needed ToRgba()

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero1TiffColor.cs

@@ -26,8 +26,8 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 
             int offset = 0;
 
-            var black = Color.Black.ToRgba32();
-            var white = Color.White.ToRgba32();
+            Color black = Color.Black;
+            Color white = Color.White;
             for (int y = top; y < top + height; y++)
             {
                 for (int x = left; x < left + width; x += 8)

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZeroTiffColor.cs

@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
         public BlackIsZeroTiffColor(ushort[] bitsPerSample)
         {
             this.bitsPerSample0 = bitsPerSample[0];
-            this.factor = (float)(1 << this.bitsPerSample0) - 1.0f;
+            this.factor = (1 << this.bitsPerSample0) - 1.0f;
         }
 
         /// <inheritdoc/>
@@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
                 for (int x = left; x < left + width; x++)
                 {
                     int value = bitReader.ReadBits(this.bitsPerSample0);
-                    float intensity = ((float)value) / this.factor;
+                    float intensity = value / this.factor;
 
                     color.FromVector4(new Vector4(intensity, intensity, intensity, 1.0f));
                     pixels[x, y] = color;

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero1TiffColor.cs

@@ -25,8 +25,8 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 
             int offset = 0;
 
-            var black = Color.Black.ToRgba32();
-            var white = Color.White.ToRgba32();
+            Color black = Color.Black;
+            Color white = Color.White;
             for (int y = top; y < top + height; y++)
             {
                 for (int x = left; x < left + width; x += 8)

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZeroTiffColor.cs

@@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
                 for (int x = left; x < left + width; x++)
                 {
                     int value = bitReader.ReadBits(this.bitsPerSample0);
-                    float intensity = 1.0f - (((float)value) / this.factor);
+                    float intensity = 1.0f - (value / this.factor);
 
                     color.FromVector4(new Vector4(intensity, intensity, intensity, 1.0f));
                     pixels[x, y] = color;