Support for encoding 8, 16 and 32 bit tga files

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -20,6 +20,11 @@ namespace SixLabors.ImageSharp.Formats.Tga
         /// </summary>
         private ImageMetadata metadata;
 
+        /// <summary>
+        /// The tga specific metadata.
+        /// </summary>
+        private TgaMetadata tgaMetadata;
+
         /// <summary>
         /// The file header containing general information about the image.
         /// </summary>
@@ -342,9 +347,9 @@ namespace SixLabors.ImageSharp.Formats.Tga
 #endif
             this.currentStream.Read(buffer, 0, TgaFileHeader.Size);
             this.fileHeader = TgaFileHeader.Parse(buffer);
-
-            // TODO: no meta data yet.
             this.metadata = new ImageMetadata();
+            this.tgaMetadata = this.metadata.GetFormatMetadata(TgaFormat.Instance);
+            this.tgaMetadata.BitsPerPixel = (TgaBitsPerPixel)this.fileHeader.PixelDepth;
         }
     }
 }

src/ImageSharp/Formats/Tga/TgaEncoderCore.cs

@@ -96,14 +96,74 @@ namespace SixLabors.ImageSharp.Formats.Tga
             Buffer2D<TPixel> pixels = image.PixelBuffer;
             switch (this.bitsPerPixel)
             {
+                case TgaBitsPerPixel.Pixel8:
+                    this.Write8Bit(stream, pixels);
+                    break;
+
+                case TgaBitsPerPixel.Pixel16:
+                    this.Write16Bit(stream, pixels);
+                    break;
+
                 case TgaBitsPerPixel.Pixel24:
                     this.Write24Bit(stream, pixels);
                     break;
+
+                case TgaBitsPerPixel.Pixel32:
+                    this.Write32Bit(stream, pixels);
+                    break;
             }
         }
 
         private IManagedByteBuffer AllocateRow(int width, int bytesPerPixel) => this.memoryAllocator.AllocatePaddedPixelRowBuffer(width, bytesPerPixel, 0);
 
+        /// <summary>
+        /// Writes the 8bit pixels uncompressed to the stream.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="stream">The <see cref="Stream"/> to write to.</param>
+        /// <param name="pixels">The <see cref="Buffer2D{TPixel}"/> containing pixel data.</param>
+        private void Write8Bit<TPixel>(Stream stream, Buffer2D<TPixel> pixels)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (IManagedByteBuffer row = this.AllocateRow(pixels.Width, 1))
+            {
+                for (int y = pixels.Height - 1; y >= 0; y--)
+                {
+                    Span<TPixel> pixelSpan = pixels.GetRowSpan(y);
+                    PixelOperations<TPixel>.Instance.ToGray8Bytes(
+                        this.configuration,
+                        pixelSpan,
+                        row.GetSpan(),
+                        pixelSpan.Length);
+                    stream.Write(row.Array, 0, row.Length());
+                }
+            }
+        }
+
+        /// <summary>
+        /// Writes the 16bit pixels uncompressed to the stream.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="stream">The <see cref="Stream"/> to write to.</param>
+        /// <param name="pixels">The <see cref="Buffer2D{TPixel}"/> containing pixel data.</param>
+        private void Write16Bit<TPixel>(Stream stream, Buffer2D<TPixel> pixels)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (IManagedByteBuffer row = this.AllocateRow(pixels.Width, 2))
+            {
+                for (int y = pixels.Height - 1; y >= 0; y--)
+                {
+                    Span<TPixel> pixelSpan = pixels.GetRowSpan(y);
+                    PixelOperations<TPixel>.Instance.ToBgra5551Bytes(
+                        this.configuration,
+                        pixelSpan,
+                        row.GetSpan(),
+                        pixelSpan.Length);
+                    stream.Write(row.Array, 0, row.Length());
+                }
+            }
+        }
+
         /// <summary>
         /// Writes the 24bit pixels uncompressed to the stream.
         /// </summary>
@@ -127,5 +187,29 @@ namespace SixLabors.ImageSharp.Formats.Tga
                 }
             }
         }
+
+        /// <summary>
+        /// Writes the 32bit pixels uncompressed to the stream.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="stream">The <see cref="Stream"/> to write to.</param>
+        /// <param name="pixels">The <see cref="Buffer2D{TPixel}"/> containing pixel data.</param>
+        private void Write32Bit<TPixel>(Stream stream, Buffer2D<TPixel> pixels)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (IManagedByteBuffer row = this.AllocateRow(pixels.Width, 4))
+            {
+                for (int y = pixels.Height - 1; y >= 0; y--)
+                {
+                    Span<TPixel> pixelSpan = pixels.GetRowSpan(y);
+                    PixelOperations<TPixel>.Instance.ToBgra32Bytes(
+                        this.configuration,
+                        pixelSpan,
+                        row.GetSpan(),
+                        pixelSpan.Length);
+                    stream.Write(row.Array, 0, row.Length());
+                }
+            }
+        }
     }
 }