Made all the Bootstrapper methods static and fixed thread safety issue.

Remove the Formats property from the Image<TColor, TPacked> class.

src/ImageSharp/Bootstrapper.cs

@@ -19,16 +19,25 @@ namespace ImageSharp
     public class Bootstrapper
     {
         /// <summary>
-        /// A new instance Initializes a new instance of the <see cref="Bootstrapper"/> class.
-        /// with lazy initialization.
+        /// A singleton of the <see cref="Bootstrapper"/> class.
         /// </summary>
-        private static readonly Lazy<Bootstrapper> Lazy = new Lazy<Bootstrapper>(() => new Bootstrapper());
+        private static readonly Bootstrapper Instance = new Bootstrapper();
 
         /// <summary>
-        /// The default list of supported <see cref="IImageFormat"/>
+        /// The list of supported <see cref="IImageFormat"/>.
         /// </summary>
         private readonly List<IImageFormat> imageFormats;
 
+        /// <summary>
+        /// The parallel options for processing tasks in parallel.
+        /// </summary>
+        private readonly ParallelOptions parallelOptions;
+
+        /// <summary>
+        /// An object that can be used to synchronize access to the <see cref="Bootstrapper"/>.
+        /// </summary>
+        private readonly object syncRoot = new object();
+
         /// <summary>
         /// Prevents a default instance of the <see cref="Bootstrapper"/> class from being created.
         /// </summary>
@@ -41,28 +50,24 @@ namespace ImageSharp
                 new PngFormat(),
                 new GifFormat()
             };
+            this.parallelOptions = new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount };
         }
 
-        /// <summary>
-        /// Gets the current bootstrapper instance.
-        /// </summary>
-        public static Bootstrapper Instance => Lazy.Value;
-
         /// <summary>
         /// Gets the collection of supported <see cref="IImageFormat"/>
         /// </summary>
-        public IReadOnlyCollection<IImageFormat> ImageFormats => new ReadOnlyCollection<IImageFormat>(this.imageFormats);
+        public static IReadOnlyCollection<IImageFormat> ImageFormats => new ReadOnlyCollection<IImageFormat>(Instance.imageFormats);
 
         /// <summary>
-        /// Gets or sets the global parallel options for processing tasks in parallel.
+        /// Gets the global parallel options for processing tasks in parallel.
         /// </summary>
-        public ParallelOptions ParallelOptions { get; set; } = new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount };
+        public static ParallelOptions ParallelOptions => Instance.parallelOptions;
 
         /// <summary>
         /// Adds a new <see cref="IImageFormat"/> to the collection of supported image formats.
         /// </summary>
         /// <param name="format">The new format to add.</param>
-        public void AddImageFormat(IImageFormat format)
+        public static void AddImageFormat(IImageFormat format)
         {
             Guard.NotNull(format, nameof(format));
             Guard.NotNull(format.Encoder, nameof(format), "The encoder should not be null.");
@@ -71,9 +76,17 @@ namespace ImageSharp
             Guard.NotNullOrEmpty(format.Extension, nameof(format), "The extension should not be null or empty.");
             Guard.NotNullOrEmpty(format.SupportedExtensions, nameof(format), "The supported extensions not be null or empty.");
 
-            GuardDuplicate(format);
+            Instance.AddImageFormatLocked(format);
+        }
 
-            this.imageFormats.Add(format);
+        private void AddImageFormatLocked(IImageFormat format)
+        {
+            lock (this.syncRoot)
+            {
+                this.GuardDuplicate(format);
+
+                this.imageFormats.Add(format);
+            }
         }
 
         private void GuardDuplicate(IImageFormat format)

src/ImageSharp/Formats/Jpg/JpegDecoderCore.cs

@@ -1286,7 +1286,7 @@ namespace ImageSharp.Formats
                 Parallel.For(
                     0,
                     height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                         {
                             int yoff = this.grayImage.GetRowOffset(y);
@@ -1324,7 +1324,7 @@ namespace ImageSharp.Formats
                 Parallel.For(
                     0,
                     height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                         {
                             int yo = this.ycbcrImage.GetRowYOffset(y);
@@ -1366,7 +1366,7 @@ namespace ImageSharp.Formats
                 Parallel.For(
                     0,
                     height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                         {
                             int yo = this.ycbcrImage.GetRowYOffset(y);

src/ImageSharp/Image/Image.cs

@@ -43,7 +43,7 @@ namespace ImageSharp
         /// </summary>
         public Image()
         {
-            this.CurrentImageFormat = Bootstrapper.Instance.ImageFormats.First(f => f.GetType() == typeof(PngFormat));
+            this.CurrentImageFormat = Bootstrapper.ImageFormats.First(f => f.GetType() == typeof(PngFormat));
         }
 
         /// <summary>
@@ -55,7 +55,7 @@ namespace ImageSharp
         public Image(int width, int height)
             : base(width, height)
         {
-            this.CurrentImageFormat = Bootstrapper.Instance.ImageFormats.First(f => f.GetType() == typeof(PngFormat));
+            this.CurrentImageFormat = Bootstrapper.ImageFormats.First(f => f.GetType() == typeof(PngFormat));
         }
 
         /// <summary>
@@ -91,11 +91,6 @@ namespace ImageSharp
             this.CopyProperties(other);
         }
 
-        /// <summary>
-        /// Gets a list of supported image formats.
-        /// </summary>
-        public IReadOnlyCollection<IImageFormat> Formats { get; } = Bootstrapper.Instance.ImageFormats;
-
         /// <summary>
         /// Gets or sets the resolution of the image in x- direction. It is defined as
         ///  number of dots per inch and should be an positive value.
@@ -288,7 +283,7 @@ namespace ImageSharp
                 Parallel.For(
                     0,
                     target.Height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                         {
                             for (int x = 0; x < target.Width; x++)
@@ -352,7 +347,7 @@ namespace ImageSharp
         /// </exception>
         private void Load(Stream stream)
         {
-            if (!this.Formats.Any())
+            if (!Bootstrapper.ImageFormats.Any())
             {
                 return;
             }
@@ -387,7 +382,7 @@ namespace ImageSharp
             StringBuilder stringBuilder = new StringBuilder();
             stringBuilder.AppendLine("Image cannot be loaded. Available formats:");
 
-            foreach (IImageFormat format in this.Formats)
+            foreach (IImageFormat format in Bootstrapper.ImageFormats)
             {
                 stringBuilder.AppendLine("-" + format);
             }
@@ -404,7 +399,7 @@ namespace ImageSharp
         /// </returns>
         private bool Decode(Stream stream)
         {
-            int maxHeaderSize = this.Formats.Max(x => x.Decoder.HeaderSize);
+            int maxHeaderSize = Bootstrapper.ImageFormats.Max(x => x.Decoder.HeaderSize);
             if (maxHeaderSize > 0)
             {
                 byte[] header = new byte[maxHeaderSize];
@@ -413,7 +408,7 @@ namespace ImageSharp
                 stream.Read(header, 0, maxHeaderSize);
                 stream.Position = 0;
 
-                IImageFormat format = this.Formats.FirstOrDefault(x => x.Decoder.IsSupportedFileFormat(header));
+                IImageFormat format = Bootstrapper.ImageFormats.FirstOrDefault(x => x.Decoder.IsSupportedFileFormat(header));
                 if (format != null)
                 {
                     format.Decoder.Decode(this, stream);

src/ImageSharp/Image/ImageFrame.cs

@@ -67,7 +67,7 @@ namespace ImageSharp
                 Parallel.For(
                     0,
                     target.Height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                     {
                         for (int x = 0; x < target.Width; x++)

src/ImageSharp/ImageProcessor.cs

@@ -18,7 +18,7 @@ namespace ImageSharp.Processors
         where TPacked : struct, IEquatable<TPacked>
     {
         /// <inheritdoc/>
-        public virtual ParallelOptions ParallelOptions { get; set; } = Bootstrapper.Instance.ParallelOptions;
+        public virtual ParallelOptions ParallelOptions { get; set; } = Bootstrapper.ParallelOptions;
 
         /// <inheritdoc/>
         public virtual bool Compand { get; set; } = false;

src/ImageSharp/Quantizers/QuantizedImage.cs

@@ -79,7 +79,7 @@ namespace ImageSharp.Quantizers
             Parallel.For(
                 0,
                 pixelCount,
-                Bootstrapper.Instance.ParallelOptions,
+                Bootstrapper.ParallelOptions,
                 i =>
                     {
                         TColor color = this.Palette[Math.Min(palletCount, this.Pixels[i])];

src/ImageSharp/Quantizers/Wu/WuQuantizer.cs

@@ -749,7 +749,7 @@ namespace ImageSharp.Quantizers
             Parallel.For(
                 0,
                 height,
-                Bootstrapper.Instance.ParallelOptions,
+                Bootstrapper.ParallelOptions,
                 y =>
                     {
                         byte[] rgba = ArrayPool<byte>.Shared.Rent(4);

tests/ImageSharp.Benchmarks/Image/CopyPixels.cs

@@ -25,7 +25,7 @@ namespace ImageSharp.Benchmarks.Image
                 Parallel.For(
                     0,
                     source.Height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                     {
                         for (int x = 0; x < source.Width; x++)
@@ -49,7 +49,7 @@ namespace ImageSharp.Benchmarks.Image
                 Parallel.For(
                     0,
                     source.Height,
-                    Bootstrapper.Instance.ParallelOptions,
+                    Bootstrapper.ParallelOptions,
                     y =>
                     {
                         sourcePixels.CopyBlock(0, y, targetPixels, 0, y, source.Width);

tests/ImageSharp.Tests/BootstrapperTests.cs

@@ -48,7 +48,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(null);
+                Bootstrapper.AddImageFormat(null);
             });
 
             var format = new TestFormat();
@@ -56,7 +56,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("decoder", exception.Message);
 
@@ -65,7 +65,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("encoder", exception.Message);
 
@@ -74,7 +74,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("mime type", exception.Message);
 
@@ -83,7 +83,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("mime type", exception.Message);
 
@@ -92,7 +92,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("extension", exception.Message);
 
@@ -101,7 +101,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("extension", exception.Message);
 
@@ -110,7 +110,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentNullException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("supported extensions", exception.Message);
 
@@ -119,7 +119,7 @@ namespace ImageSharp.Tests
 
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("supported extensions", exception.Message);
         }
@@ -131,28 +131,28 @@ namespace ImageSharp.Tests
 
             var exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("format with the same", exception.Message);
 
             format.Extension = "test";
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("should contain", exception.Message);
 
             format.SupportedExtensions = new string[] { "test", "jpg" };
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("supports the same", exception.Message);
 
             format.SupportedExtensions = new string[] { "test", "" };
             exception = Assert.Throws<ArgumentException>(() =>
             {
-                Bootstrapper.Instance.AddImageFormat(format);
+                Bootstrapper.AddImageFormat(format);
             });
             Assert.Contains("empty values", exception.Message);
         }