Merge pull request #537 from carbon/jpeg-cleanup

Improve JPEG CQ

Author: JimBobSquarePants

src/ImageSharp/Formats/Jpeg/Common/Decoder/ProfileResolver.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Text;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Common.Decoder
 {
@@ -13,22 +14,22 @@ internal static class ProfileResolver
         /// <summary>
         /// Describes the EXIF specific markers
         /// </summary>
-        public static readonly byte[] JFifMarker = ToAsciiBytes("JFIF\0");
+        public static readonly byte[] JFifMarker = Encoding.UTF8.GetBytes("JFIF\0");
 
         /// <summary>
         /// Describes the EXIF specific markers
         /// </summary>
-        public static readonly byte[] IccMarker = ToAsciiBytes("ICC_PROFILE\0");
+        public static readonly byte[] IccMarker = Encoding.UTF8.GetBytes("ICC_PROFILE\0");
 
         /// <summary>
         /// Describes the ICC specific markers
         /// </summary>
-        public static readonly byte[] ExifMarker = ToAsciiBytes("Exif\0\0");
+        public static readonly byte[] ExifMarker = Encoding.UTF8.GetBytes("Exif\0\0");
 
         /// <summary>
         /// Describes Adobe specific markers <see href="http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe"/>
         /// </summary>
-        public static readonly byte[] AdobeMarker = ToAsciiBytes("Adobe");
+        public static readonly byte[] AdobeMarker = Encoding.UTF8.GetBytes("Adobe");
 
         /// <summary>
         /// Returns a value indicating whether the passed bytes are a match to the profile identifer
@@ -41,19 +42,5 @@ public static bool IsProfile(Span<byte> bytesToCheck, Span<byte> profileIdentifi
             return bytesToCheck.Length >= profileIdentifier.Length
                    && bytesToCheck.Slice(0, profileIdentifier.Length).SequenceEqual(profileIdentifier);
         }
-
-        // No Encoding.ASCII nor Linq.Select on NetStandard 1.1
-        private static byte[] ToAsciiBytes(string str)
-        {
-            int length = str.Length;
-            byte[] bytes = new byte[length];
-            char[] chars = str.ToCharArray();
-            for (int i = 0; i < length; i++)
-            {
-                bytes[i] = (byte)chars[i];
-            }
-
-            return bytes;
-        }
     }
 }

src/ImageSharp/Formats/Jpeg/IJpegDecoderOptions.cs

@@ -1,11 +1,6 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
-using System.Collections.Generic;
-using System.IO;
-using SixLabors.ImageSharp.PixelFormats;
-
 namespace SixLabors.ImageSharp.Formats.Jpeg
 {
     /// <summary>
@@ -18,4 +13,4 @@ internal interface IJpegDecoderOptions
         /// </summary>
         bool IgnoreMetadata { get; }
     }
-}
+}

src/ImageSharp/Formats/Jpeg/IJpegEncoderOptions.cs

@@ -1,11 +1,6 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
-using System.Collections.Generic;
-using System.IO;
-using SixLabors.ImageSharp.PixelFormats;
-
 namespace SixLabors.ImageSharp.Formats.Jpeg
 {
     /// <summary>
@@ -31,4 +26,4 @@ internal interface IJpegEncoderOptions
         /// <value>The subsample ratio of the jpg image.</value>
         JpegSubsample? Subsample { get; }
     }
-}
+}

src/ImageSharp/Formats/Jpeg/ImageExtensions.cs

@@ -1,10 +1,8 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
 using System.IO;
 using SixLabors.ImageSharp.Advanced;
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.PixelFormats;
 

src/ImageSharp/Formats/Jpeg/JpegConfigurationModule.cs

@@ -17,4 +17,4 @@ public void Configure(Configuration config)
             config.ImageFormatsManager.AddImageFormatDetector(new JpegImageFormatDetector());
         }
     }
-}
+}

src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs

@@ -16,12 +16,7 @@ public sealed class JpegImageFormatDetector : IImageFormatDetector
         /// <inheritdoc/>
         public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
         {
-            if (this.IsSupportedFileFormat(header))
-            {
-                return ImageFormats.Jpeg;
-            }
-
-            return null;
+            return this.IsSupportedFileFormat(header) ? ImageFormats.Jpeg : null;
         }
 
         private bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
@@ -35,51 +30,33 @@ private bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
         /// </summary>
         /// <param name="header">The bytes representing the file header.</param>
         /// <returns>The <see cref="bool"/></returns>
-        private bool IsJfif(ReadOnlySpan<byte> header)
-        {
-            // TODO: This should be in constants
-            bool isJfif =
-                header[6] == 0x4A && // J
-                header[7] == 0x46 && // F
-                header[8] == 0x49 && // I
-                header[9] == 0x46 && // F
-                header[10] == 0x00;
-
-            return isJfif;
-        }
+        private bool IsJfif(ReadOnlySpan<byte> header) =>
+            header[6] == 0x4A && // J
+            header[7] == 0x46 && // F
+            header[8] == 0x49 && // I
+            header[9] == 0x46 && // F
+            header[10] == 0x00;
 
         /// <summary>
         /// Returns a value indicating whether the given bytes identify EXIF data.
         /// </summary>
         /// <param name="header">The bytes representing the file header.</param>
         /// <returns>The <see cref="bool"/></returns>
-        private bool IsExif(ReadOnlySpan<byte> header)
-        {
-            // TODO: This should be in constants
-            bool isExif =
-                header[6] == 0x45 && // E
-                header[7] == 0x78 && // X
-                header[8] == 0x69 && // I
-                header[9] == 0x66 && // F
-                header[10] == 0x00;
-
-            return isExif;
-        }
+        private bool IsExif(ReadOnlySpan<byte> header) =>
+            header[6] == 0x45 && // E
+            header[7] == 0x78 && // X
+            header[8] == 0x69 && // I
+            header[9] == 0x66 && // F
+            header[10] == 0x00;
 
         /// <summary>
         /// Returns a value indicating whether the given bytes identify Jpeg data.
         /// This is a last chance resort for jpegs that contain ICC information.
         /// </summary>
         /// <param name="header">The bytes representing the file header.</param>
         /// <returns>The <see cref="bool"/></returns>
-        private bool IsJpeg(ReadOnlySpan<byte> header)
-        {
-            // TODO: This should be in constants
-            bool isJpg =
-                header[0] == 0xFF && // 255
-                header[1] == 0xD8; // 216
-
-            return isJpg;
-        }
+        private bool IsJpeg(ReadOnlySpan<byte> header) =>
+            header[0] == 0xFF && // 255
+            header[1] == 0xD8; // 216
     }
 }

src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsFrameComponent.cs

@@ -17,7 +17,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
     internal class PdfJsFrameComponent : IDisposable, IJpegComponent
     {
         private readonly MemoryManager memoryManager;
-#pragma warning disable SA1401 // Fields should be private
 
         public PdfJsFrameComponent(MemoryManager memoryManager, PdfJsFrame frame, byte id, int horizontalFactor, int verticalFactor, byte quantizationTableIndex, int index)
         {

src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTable.cs

@@ -40,7 +40,7 @@ internal unsafe struct PdfJsHuffmanTable
         /// <param name="memoryManager">The <see cref="MemoryManager"/> to use for buffer allocations.</param>
         /// <param name="lengths">The code lengths</param>
         /// <param name="values">The huffman values</param>
-        public PdfJsHuffmanTable(MemoryManager memoryManager, byte[] lengths, byte[] values)
+        public PdfJsHuffmanTable(MemoryManager memoryManager, ReadOnlySpan<byte> lengths, ReadOnlySpan<byte> values)
         {
             const int length = 257;
             using (IBuffer<short> huffsize = memoryManager.Allocate<short>(length))
@@ -57,10 +57,9 @@ public PdfJsHuffmanTable(MemoryManager memoryManager, byte[] lengths, byte[] val
 
             fixed (byte* huffValRef = this.HuffVal.Data)
             {
-                for (int i = 0; i < values.Length; i++)
-                {
-                    huffValRef[i] = values[i];
-                }
+                var huffValSpan = new Span<byte>(huffValRef, 256);
+
+                values.CopyTo(huffValSpan);
             }
         }
 
@@ -69,7 +68,7 @@ public PdfJsHuffmanTable(MemoryManager memoryManager, byte[] lengths, byte[] val
         /// </summary>
         /// <param name="lengths">The code lengths</param>
         /// <param name="huffsizeRef">The huffman size span ref</param>
-        private static void GenerateSizeTable(byte[] lengths, ref short huffsizeRef)
+        private static void GenerateSizeTable(ReadOnlySpan<byte> lengths, ref short huffsizeRef)
         {
             short index = 0;
             for (short l = 1; l <= 16; l++)
@@ -115,7 +114,7 @@ private static void GenerateCodeTable(ref short huffsizeRef, ref short huffcodeR
         /// </summary>
         /// <param name="lengths">The code lengths</param>
         /// <param name="huffcodeRef">The huffman code span ref</param>
-        private void GenerateDecoderTables(byte[] lengths, ref short huffcodeRef)
+        private void GenerateDecoderTables(ReadOnlySpan<byte> lengths, ref short huffcodeRef)
         {
             fixed (short* valOffsetRef = this.ValOffset.Data)
             fixed (long* maxcodeRef = this.MaxCode.Data)
@@ -147,18 +146,17 @@ private void GenerateDecoderTables(byte[] lengths, ref short huffcodeRef)
         /// <param name="lengths">The code lengths</param>
         /// <param name="huffval">The huffman value array</param>
         /// <param name="huffcodeRef">The huffman code span ref</param>
-        private void GenerateLookaheadTables(byte[] lengths, byte[] huffval, ref short huffcodeRef)
+        private void GenerateLookaheadTables(ReadOnlySpan<byte> lengths, ReadOnlySpan<byte> huffval, ref short huffcodeRef)
         {
             // TODO: This generation code matches the libJpeg code but the lookahead table is not actually used yet.
             // To use it we need to implement fast lookup path in PdfJsScanDecoder.DecodeHuffman
             // This should yield much faster scan decoding as usually, more than 95% of the Huffman codes
             // will be 8 or fewer bits long and can be handled without looping.
             fixed (short* lookaheadRef = this.Lookahead.Data)
             {
-                for (int i = 0; i < 256; i++)
-                {
-                    lookaheadRef[i] = 2034; // 9 << 8;
-                }
+                var lookaheadSpan = new Span<short>(lookaheadRef, 256);
+
+                lookaheadSpan.Fill(2034); // 9 << 8;
 
                 int p = 0;
                 for (int l = 1; l <= 8; l++)

src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTables.cs

@@ -21,10 +21,7 @@ internal sealed class PdfJsHuffmanTables
         public ref PdfJsHuffmanTable this[int index]
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get
-            {
-                return ref this.tables[index];
-            }
+            get => ref this.tables[index];
         }
     }
 }

src/ImageSharp/Formats/Jpeg/PdfJsPort/PdfJsJpegDecoderCore.cs

@@ -7,7 +7,6 @@
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Formats.Jpeg.Common;
 using SixLabors.ImageSharp.Formats.Jpeg.Common.Decoder;
 using SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components;
@@ -367,14 +366,9 @@ private JpegColorSpace DeduceJpegColorSpace()
 
             if (this.ComponentCount == 4)
             {
-                if (this.adobe.ColorTransform == PdfJsJpegConstants.Markers.Adobe.ColorTransformYcck)
-                {
-                    return JpegColorSpace.Ycck;
-                }
-                else
-                {
-                    return JpegColorSpace.Cmyk;
-                }
+                return this.adobe.ColorTransform == PdfJsJpegConstants.Markers.Adobe.ColorTransformYcck
+                    ? JpegColorSpace.Ycck
+                    : JpegColorSpace.Cmyk;
             }
 
             throw new ImageFormatException($"Unsupported color mode. Max components 4; found {this.ComponentCount}");
@@ -700,8 +694,8 @@ private void ProcessDefineHuffmanTablesMarker(int remaining)
                             this.BuildHuffmanTable(
                                 huffmanTableSpec >> 4 == 0 ? this.dcHuffmanTables : this.acHuffmanTables,
                                 huffmanTableSpec & 15,
-                                codeLengths.Array,
-                                huffmanValues.Array);
+                                codeLengths.Span,
+                                huffmanValues.Span);
                         }
                     }
                 }
@@ -785,7 +779,7 @@ private void ProcessStartOfScanMarker()
         /// <param name="codeLengths">The codelengths</param>
         /// <param name="values">The values</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private void BuildHuffmanTable(PdfJsHuffmanTables tables, int index, byte[] codeLengths, byte[] values)
+        private void BuildHuffmanTable(PdfJsHuffmanTables tables, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
         {
             tables[index] = new PdfJsHuffmanTable(this.configuration.MemoryManager, codeLengths, values);
         }