Fixing file type detection

Former-commit-id: 111a537976f3adfc876d502855a5933d2b530180

src/ImageProcessor/Imaging/Formats/BitmapFormat.cs

@@ -19,13 +19,13 @@ namespace ImageProcessor.Imaging.Formats
     public class BitmapFormat : FormatBase
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public override byte[] FileHeader
+        public override byte[][] FileHeaders
         {
             get
             {
-                return Encoding.ASCII.GetBytes("BM");
+                return new[] { Encoding.ASCII.GetBytes("BM") };
             }
         }
 

src/ImageProcessor/Imaging/Formats/FormatBase.cs

@@ -21,9 +21,9 @@ namespace ImageProcessor.Imaging.Formats
     public abstract class FormatBase : ISupportedImageFormat
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public abstract byte[] FileHeader { get; }
+        public abstract byte[][] FileHeaders { get; }
 
         /// <summary>
         /// Gets the list of file extensions.

src/ImageProcessor/Imaging/Formats/FormatUtilities.cs

@@ -43,14 +43,18 @@ namespace ImageProcessor.Imaging.Formats
             byte[] buffer = new byte[4];
             stream.Read(buffer, 0, buffer.Length);
 
-            // ReSharper disable once LoopCanBeConvertedToQuery
             foreach (ISupportedImageFormat supportedImageFormat in supportedImageFormats)
             {
-                byte[] header = supportedImageFormat.FileHeader;
-                if (header.SequenceEqual(buffer.Take(header.Length)))
+                byte[][] headers = supportedImageFormat.FileHeaders;
+
+                // ReSharper disable once LoopCanBeConvertedToQuery
+                foreach (byte[] header in headers)
                 {
-                    stream.Position = 0;
-                    return supportedImageFormat;
+                    if (header.SequenceEqual(buffer.Take(header.Length)))
+                    {
+                        stream.Position = 0;
+                        return supportedImageFormat;
+                    }
                 }
             }
 

src/ImageProcessor/Imaging/Formats/GifFormat.cs

@@ -23,13 +23,13 @@ namespace ImageProcessor.Imaging.Formats
     public class GifFormat : FormatBase
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public override byte[] FileHeader
+        public override byte[][] FileHeaders
         {
             get
             {
-                return Encoding.ASCII.GetBytes("GIF");
+                return new[] { Encoding.ASCII.GetBytes("GIF") };
             }
         }
 

src/ImageProcessor/Imaging/Formats/ISupportedImageFormat.cs

@@ -21,9 +21,9 @@ namespace ImageProcessor.Imaging.Formats
     public interface ISupportedImageFormat
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        byte[] FileHeader { get; }
+        byte[][] FileHeaders { get; }
 
         /// <summary>
         /// Gets the list of file extensions.

src/ImageProcessor/Imaging/Formats/JpegFormat.cs

@@ -23,13 +23,13 @@ namespace ImageProcessor.Imaging.Formats
     public sealed class JpegFormat : FormatBase
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public override byte[] FileHeader
+        public override byte[][] FileHeaders
         {
             get
             {
-                return new byte[] { 255, 216, 255 };
+                return new[] { new byte[] { 255, 216, 255 } };
             }
         }
 

src/ImageProcessor/Imaging/Formats/PngFormat.cs

@@ -20,13 +20,13 @@ namespace ImageProcessor.Imaging.Formats
     public class PngFormat : FormatBase
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public override byte[] FileHeader
+        public override byte[][] FileHeaders
         {
             get
             {
-                return new byte[] { 137, 80, 78, 71 };
+                return new[] { new byte[] { 137, 80, 78, 71 } };
             }
         }
 

src/ImageProcessor/Imaging/Formats/TiffFormat.cs

@@ -21,13 +21,17 @@ namespace ImageProcessor.Imaging.Formats
     public class TiffFormat : FormatBase
     {
         /// <summary>
-        /// Gets the file header.
+        /// Gets the file headers.
         /// </summary>
-        public override byte[] FileHeader
+        public override byte[][] FileHeaders
         {
             get
             {
-                return new byte[] { 77, 77, 42 };
+                return new[]
+                { 
+                    new byte[] { 73, 73, 42 }, 
+                    new byte[] { 77, 77, 42 } 
+                };
             }
         }