document and refactor GetRgb24()

src/ImageSharp/Common/Extensions/ByteExtensions.cs

@@ -5,10 +5,13 @@
 
 namespace ImageSharp
 {
+    using System;
     using System.Runtime.CompilerServices;
 
+    using ImageSharp.PixelFormats;
+
     /// <summary>
-    /// Extension methods for the <see cref="byte"/> struct.
+    /// Extension methods for the <see cref="byte"/> struct buffers.
     /// </summary>
     internal static class ByteExtensions
     {
@@ -44,5 +47,45 @@ namespace ImageSharp
                 j--;
             }
         }
+
+        /// <summary>
+        /// Returns a reference to the given position of the array unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
+        /// </summary>
+        /// <param name="bytes">The byte array.</param>
+        /// <param name="offset">The offset in bytes.</param>
+        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref Rgb24 GetRgb24(this byte[] bytes, int offset)
+        {
+            DebugGuard.MustBeLessThan(offset + 2, bytes.Length, nameof(offset));
+
+            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
+        }
+
+        /// <summary>
+        /// Returns a reference to the given position of the span unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
+        /// </summary>
+        /// <param name="bytes">The byte span.</param>
+        /// <param name="offset">The offset in bytes.</param>
+        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref Rgb24 GetRgb24(this Span<byte> bytes, int offset)
+        {
+            DebugGuard.MustBeLessThan(offset + 2, bytes.Length, nameof(offset));
+
+            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
+        }
+
+        /// <summary>
+        ///  Returns a reference to the given position of the buffer pointed by `baseRef` unsafe casted to <see cref="ImageSharp.PixelFormats.Rgb24"/>.
+        /// </summary>
+        /// <param name="baseRef">A reference to the beginning of the buffer</param>
+        /// <param name="offset">The offset in bytes.</param>
+        /// <returns>The <see cref="ImageSharp.PixelFormats.Rgb24"/> reference at the given offset.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref Rgb24 GetRgb24(ref byte baseRef, int offset)
+        {
+            return ref Unsafe.As<byte, Rgb24>(ref Unsafe.Add(ref baseRef, offset));
+        }
     }
 }

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -249,15 +249,11 @@ namespace ImageSharp.Formats
             for (int y = 0; y < height; y++)
             {
                 int newY = Invert(y, height, inverted);
-
-                // TODO: Could use PixelOperations here!
-
                 this.currentStream.Read(row, 0, row.Length);
-
                 int offset = 0;
-
                 Span<TPixel> pixelRow = pixels.GetRowSpan(y);
 
+                // TODO: Could use PixelOperations here!
                 for (int x = 0; x < arrayWidth; x++)
                 {
                     int colOffset = x * ppb;

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -448,7 +448,7 @@ namespace ImageSharp.Formats
                         int indexOffset = index * 3;
 
                         ref TPixel pixel = ref rowSpan[x];
-                        rgba.Rgb = Rgb24.AsRgb24(colorTable, indexOffset);
+                        rgba.Rgb = colorTable.GetRgb24(indexOffset);
 
                         pixel.PackFromRgba32(rgba);
                     }

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -643,7 +643,7 @@ namespace ImageSharp.Formats
 
                     if (rgba.A > 0)
                     {
-                        rgba.Rgb = Rgb24.AsRgb24(palette, pixelOffset);
+                        rgba.Rgb = palette.GetRgb24(pixelOffset);
                     }
                     else
                     {
@@ -663,7 +663,7 @@ namespace ImageSharp.Formats
                     int index = newScanline[x + 1];
                     int pixelOffset = index * 3;
 
-                    rgba.Rgb = Rgb24.AsRgb24(palette, pixelOffset);
+                    rgba.Rgb = palette.GetRgb24(pixelOffset);
 
                     color.PackFromRgba32(rgba);
                     row[x] = color;
@@ -728,7 +728,7 @@ namespace ImageSharp.Formats
 
                             if (rgba.A > 0)
                             {
-                                rgba.Rgb = Rgb24.AsRgb24(this.palette, offset);
+                                rgba.Rgb = this.palette.GetRgb24(offset);
                             }
                             else
                             {
@@ -748,7 +748,7 @@ namespace ImageSharp.Formats
                             int index = newScanline[o];
                             int offset = index * 3;
 
-                            rgba.Rgb = Rgb24.AsRgb24(this.palette, offset);
+                            rgba.Rgb = this.palette.GetRgb24(offset);
 
                             color.PackFromRgba32(rgba);
                             rowSpan[x] = color;

src/ImageSharp/PixelFormats/PixelConversionExtensions.cs

@@ -21,7 +21,7 @@
         public static void ToXyzBytes<TPixel>(this TPixel pixel, Span<byte> bytes, int startIndex)
             where TPixel : struct, IPixel<TPixel>
         {
-            ref Rgb24 dest = ref Rgb24.AsRgb24(bytes, startIndex);
+            ref Rgb24 dest = ref bytes.GetRgb24(startIndex);
             pixel.ToRgb24(ref dest);
         }
 

src/ImageSharp/PixelFormats/Rgb24.cs

@@ -111,23 +111,5 @@ namespace ImageSharp.PixelFormats
         {
             throw new NotImplementedException();
         }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static ref Rgb24 AsRgb24(byte[] bytes, int offset)
-        {
-            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal static ref Rgb24 AsRgb24(ref byte baseRef, int offset)
-        {
-            return ref Unsafe.As<byte, Rgb24>(ref Unsafe.Add(ref baseRef, offset));
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static ref Rgb24 AsRgb24(Span<byte> bytes, int offset)
-        {
-            return ref Unsafe.As<byte, Rgb24>(ref bytes[offset]);
-        }
     }
 }