Perf improvements for gifs.

Former-commit-id: a27a0e1430a517c1c8e7eaae36683b1bf570ec35
Former-commit-id: f80be4bfdc25ff9a36ec0fac3dc25c118f0b6750
Former-commit-id: 25f58830f4b4b7969b340c28faf3943afb107536

src/ImageProcessor/Formats/Gif/GifDecoderCore.cs

@@ -7,6 +7,7 @@ namespace ImageProcessor.Formats
 {
     using System;
     using System.IO;
+    using System.Threading.Tasks;
 
     /// <summary>
     /// Performs the gif decoding operation.
@@ -404,19 +405,20 @@ namespace ImageProcessor.Formats
             {
                 if (this.graphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToBackground)
                 {
-                    for (int y = descriptor.Top; y < descriptor.Top + descriptor.Height; y++)
-                    {
-                        for (int x = descriptor.Left; x < descriptor.Left + descriptor.Width; x++)
-                        {
-                            offset = ((y * imageWidth) + x) * 4;
-
-                            // Stored in r-> g-> b-> a order.
-                            this.currentFrame[offset + 0] = 0;
-                            this.currentFrame[offset + 1] = 0;
-                            this.currentFrame[offset + 2] = 0;
-                            this.currentFrame[offset + 3] = 0;
-                        }
-                    }
+                    Parallel.For(descriptor.Top, descriptor.Top + descriptor.Height,
+                        y =>
+                            {
+                                for (int x = descriptor.Left; x < descriptor.Left + descriptor.Width; x++)
+                                {
+                                    offset = ((y * imageWidth) + x) * 4;
+
+                                    // Stored in r-> g-> b-> a order.
+                                    this.currentFrame[offset + 0] = 0;
+                                    this.currentFrame[offset + 1] = 0;
+                                    this.currentFrame[offset + 2] = 0;
+                                    this.currentFrame[offset + 3] = 0;
+                                }
+                            });
                 }
                 else if (this.graphicsControlExtension.DisposalMethod == DisposalMethod.RestoreToPrevious)
                 {

src/ImageProcessor/Formats/Gif/GifEncoder.cs

@@ -8,6 +8,7 @@ namespace ImageProcessor.Formats
     using System;
     using System.IO;
     using System.Linq;
+    using System.Threading.Tasks;
 
     /// <summary>
     /// Image encoder for writing image data to a stream in gif format.
@@ -148,15 +149,16 @@ namespace ImageProcessor.Formats
             int colorTableLength = (int)Math.Pow(2, bitDepth) * 3;
             byte[] colorTable = new byte[colorTableLength];
 
-            for (int i = 0; i < pixelCount; i++)
-            {
-                int offset = i * 3;
-                Bgra32 color = Color.ToNonPremultiplied(pallete[i]);
+            Parallel.For(0, pixelCount,
+                i =>
+                    {
+                        int offset = i * 3;
+                        Bgra32 color = Color.ToNonPremultiplied(pallete[i]);
 
-                colorTable[offset] = color.R;
-                colorTable[offset + 1] = color.G;
-                colorTable[offset + 2] = color.B;
-            }
+                        colorTable[offset] = color.R;
+                        colorTable[offset + 1] = color.G;
+                        colorTable[offset + 2] = color.B;
+                    });
 
             stream.Write(colorTable, 0, colorTableLength);
 

src/ImageProcessor/Formats/Gif/Quantizer/QuantizedImage.cs

@@ -6,6 +6,7 @@
 namespace ImageProcessor.Formats
 {
     using System;
+    using System.Threading.Tasks;
 
     /// <summary>
     /// Represents a quantized image where the pixels indexed by a color palette.
@@ -72,15 +73,16 @@ namespace ImageProcessor.Formats
             int palletCount = this.Palette.Length - 1;
             float[] bgraPixels = new float[pixelCount * 4];
 
-            for (int i = 0; i < pixelCount; i++)
-            {
-                int offset = i * 4;
-                Color color = this.Palette[Math.Min(palletCount, this.Pixels[i])];
-                bgraPixels[offset] = color.R;
-                bgraPixels[offset + 1] = color.G;
-                bgraPixels[offset + 2] = color.B;
-                bgraPixels[offset + 3] = color.A;
-            }
+            Parallel.For(0, pixelCount,
+                i =>
+                    {
+                        int offset = i * 4;
+                        Color color = this.Palette[Math.Min(palletCount, this.Pixels[i])];
+                        bgraPixels[offset] = color.R;
+                        bgraPixels[offset + 1] = color.G;
+                        bgraPixels[offset + 2] = color.B;
+                        bgraPixels[offset + 3] = color.A;
+                    });
 
             image.SetPixels(this.Width, this.Height, bgraPixels);
             return image;