Removes usage of linq in several critical paths

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

@@ -12,17 +12,17 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
     internal static class ProfileResolver
     {
         /// <summary>
-        /// Describes the EXIF specific markers.
+        /// Describes the JFIF specific markers.
         /// </summary>
         public static readonly byte[] JFifMarker = Encoding.ASCII.GetBytes("JFIF\0");
 
         /// <summary>
-        /// Describes the EXIF specific markers.
+        /// Describes the ICC specific markers.
         /// </summary>
         public static readonly byte[] IccMarker = Encoding.ASCII.GetBytes("ICC_PROFILE\0");
 
         /// <summary>
-        /// Describes the ICC specific markers.
+        /// Describes the EXIF specific markers.
         /// </summary>
         public static readonly byte[] ExifMarker = Encoding.ASCII.GetBytes("Exif\0\0");
 
@@ -36,7 +36,7 @@ internal static class ProfileResolver
         /// </summary>
         /// <param name="bytesToCheck">The bytes to check.</param>
         /// <param name="profileIdentifier">The profile identifier.</param>
-        /// <returns>The <see cref="bool"/></returns>
+        /// <returns>The <see cref="bool"/>.</returns>
         public static bool IsProfile(ReadOnlySpan<byte> bytesToCheck, ReadOnlySpan<byte> profileIdentifier)
         {
             return bytesToCheck.Length >= profileIdentifier.Length

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Buffers.Binary;
 using System.IO;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Common.Helpers;
@@ -726,7 +725,7 @@ private void ProcessStartOfFrameMarker(int remaining, in JpegFileMarker frameMar
             this.InputStream.Read(this.temp, 0, length);
 
             // We only support 8-bit and 12-bit precision.
-            if (!this.supportedPrecisions.Contains(this.temp[0]))
+            if (Array.IndexOf(this.supportedPrecisions, this.temp[0]) == -1)
             {
                 JpegThrowHelper.ThrowImageFormatException("Only 8-Bit and 12-Bit precision supported.");
             }

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Buffers.Binary;
 using System.IO;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Jpeg.Components;
@@ -197,7 +196,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             Guard.NotNull(image, nameof(image));
             Guard.NotNull(stream, nameof(stream));
 
-            ushort max = JpegConstants.MaxLength;
+            const ushort max = JpegConstants.MaxLength;
             if (image.Width >= max || image.Height >= max)
             {
                 throw new ImageFormatException($"Image is too large to encode at {image.Width}x{image.Height}.");
@@ -226,7 +225,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             InitQuantizationTable(1, scale, ref this.chrominanceQuantTable);
 
             // Compute number of components based on input image type.
-            int componentCount = 3;
+            const int componentCount = 3;
 
             // Write the Start Of Image marker.
             this.WriteApplicationHeader(metadata);
@@ -278,7 +277,7 @@ private static void WriteDataToDqt(byte[] dqt, ref int offset, QuantIndex i, ref
         private static void InitQuantizationTable(int i, int scale, ref Block8x8F quant)
         {
             DebugGuard.MustBeBetweenOrEqualTo(i, 0, 1, nameof(i));
-            var unscaledQuant = (i == 0) ? UnscaledQuant_Luminance : UnscaledQuant_Chrominance;
+            ReadOnlySpan<byte> unscaledQuant = (i == 0) ? UnscaledQuant_Luminance : UnscaledQuant_Chrominance;
 
             for (int j = 0; j < Block8x8F.Size; j++)
             {
@@ -653,8 +652,8 @@ private void WriteExifProfile(ExifProfile exifProfile)
                 return;
             }
 
-            const int MaxBytesApp1 = 65533;
-            const int MaxBytesWithExifId = 65527;
+            const int MaxBytesApp1 = 65533; // 64k - 2 padding bytes
+            const int MaxBytesWithExifId = 65527; // Max - 6 bytes for EXIF header.
 
             byte[] data = exifProfile?.ToByteArray();
 
@@ -663,31 +662,30 @@ private void WriteExifProfile(ExifProfile exifProfile)
                 return;
             }
 
-            data = ProfileResolver.ExifMarker.Concat(data).ToArray();
-
-            int remaining = data.Length;
+            // We can write up to a maximum of 64 data to the initial marker so calculate boundaries.
+            int exifMarkerLength = ProfileResolver.ExifMarker.Length;
+            int remaining = exifMarkerLength + data.Length;
             int bytesToWrite = remaining > MaxBytesApp1 ? MaxBytesApp1 : remaining;
             int app1Length = bytesToWrite + 2;
 
+            // Write the app marker, EXIF marker, and data
             this.WriteApp1Header(app1Length);
-
-            // write the exif data
-            this.outputStream.Write(data, 0, bytesToWrite);
+            this.outputStream.Write(ProfileResolver.ExifMarker);
+            this.outputStream.Write(data, 0, bytesToWrite - exifMarkerLength);
             remaining -= bytesToWrite;
 
-            // if the exif data exceeds 64K, write it in multiple APP1 Markers
-            for (int idx = MaxBytesApp1; idx < data.Length; idx += MaxBytesWithExifId)
+            // If the exif data exceeds 64K, write it in multiple APP1 Markers
+            for (int idx = MaxBytesWithExifId; idx < data.Length; idx += MaxBytesWithExifId)
             {
                 bytesToWrite = remaining > MaxBytesWithExifId ? MaxBytesWithExifId : remaining;
-                app1Length = bytesToWrite + 2 + 6;
+                app1Length = bytesToWrite + 2 + exifMarkerLength;
 
                 this.WriteApp1Header(app1Length);
 
-                // write Exif00 marker
-                ProfileResolver.ExifMarker.AsSpan().CopyTo(this.buffer.AsSpan());
-                this.outputStream.Write(this.buffer, 0, 6);
+                // Write Exif00 marker
+                this.outputStream.Write(ProfileResolver.ExifMarker);
 
-                // write the exif data
+                // Write the exif data
                 this.outputStream.Write(data, idx, bytesToWrite);
 
                 remaining -= bytesToWrite;

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -6,7 +6,6 @@
 using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
@@ -231,7 +230,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             if (this.pngColorType == PngColorType.Palette)
             {
                 byte bits = (byte)this.pngBitDepth;
-                if (!ColorTypes[this.pngColorType.Value].Contains(bits))
+                if (Array.IndexOf(ColorTypes[this.pngColorType.Value], bits) == -1)
                 {
                     throw new NotSupportedException("Bit depth is not supported or not valid.");
                 }
@@ -268,7 +267,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             else
             {
                 this.bitDepth = (byte)this.pngBitDepth;
-                if (!ColorTypes[this.pngColorType.Value].Contains(this.bitDepth))
+                if (Array.IndexOf(ColorTypes[this.pngColorType.Value], this.bitDepth) == -1)
                 {
                     throw new NotSupportedException("Bit depth is not supported or not valid.");
                 }

src/ImageSharp/MetaData/Profiles/ICC/Curves/IccOneDimensionalCurve.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Linq;
 
 namespace SixLabors.ImageSharp.Metadata.Profiles.Icc
 {
@@ -52,7 +51,7 @@ public bool Equals(IccOneDimensionalCurve other)
             }
 
             return this.BreakPoints.AsSpan().SequenceEqual(other.BreakPoints)
-                && this.Segments.SequenceEqual(other.Segments);
+                && this.Segments.AsSpan().SequenceEqual(other.Segments);
         }
     }
 }

src/ImageSharp/MetaData/Profiles/ICC/Curves/IccResponseCurve.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Linq;
 using System.Numerics;
 
 namespace SixLabors.ImageSharp.Metadata.Profiles.Icc
@@ -65,10 +64,7 @@ public bool Equals(IccResponseCurve other)
         }
 
         /// <inheritdoc />
-        public override bool Equals(object obj)
-        {
-            return obj is IccResponseCurve other && this.Equals(other);
-        }
+        public override bool Equals(object obj) => obj is IccResponseCurve other && this.Equals(other);
 
         /// <inheritdoc />
         public override int GetHashCode()
@@ -88,7 +84,7 @@ private bool EqualsResponseArray(IccResponseCurve other)
 
             for (int i = 0; i < this.ResponseArrays.Length; i++)
             {
-                if (!this.ResponseArrays[i].SequenceEqual(other.ResponseArrays[i]))
+                if (!this.ResponseArrays[i].AsSpan().SequenceEqual(other.ResponseArrays[i]))
                 {
                     return false;
                 }

src/ImageSharp/MetaData/Profiles/ICC/DataWriter/IccDataWriter.TagDataEntry.cs

@@ -163,10 +163,7 @@ public int WriteTagDataEntryHeader(IccTypeSignature signature)
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteUnknownTagDataEntry(IccUnknownTagDataEntry value)
-        {
-            return this.WriteArray(value.Data);
-        }
+        public int WriteUnknownTagDataEntry(IccUnknownTagDataEntry value) => this.WriteArray(value.Data);
 
         /// <summary>
         /// Writes a <see cref="IccChromaticityTagDataEntry"/>
@@ -269,10 +266,7 @@ public int WriteDataTagDataEntry(IccDataTagDataEntry value)
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteDateTimeTagDataEntry(IccDateTimeTagDataEntry value)
-        {
-            return this.WriteDateTime(value.Value);
-        }
+        public int WriteDateTimeTagDataEntry(IccDateTimeTagDataEntry value) => this.WriteDateTime(value.Value);
 
         /// <summary>
         /// Writes a <see cref="IccLut16TagDataEntry"/>
@@ -563,6 +557,7 @@ public int WriteMultiLocalizedUnicodeTagDataEntry(IccMultiLocalizedUnicodeTagDat
             long tpos = this.dataStream.Position;
             this.dataStream.Position += cultureCount * 12;
 
+            // TODO: Investigate cost of Linq GroupBy
             IGrouping<string, IccLocalizedString>[] texts = value.Texts.GroupBy(t => t.Text).ToArray();
 
             uint[] offset = new uint[texts.Length];
@@ -625,7 +620,7 @@ public int WriteMultiProcessElementsTagDataEntry(IccMultiProcessElementsTagDataE
             long tpos = this.dataStream.Position;
             this.dataStream.Position += value.Data.Length * 8;
 
-            IccPositionNumber[] posTable = new IccPositionNumber[value.Data.Length];
+            var posTable = new IccPositionNumber[value.Data.Length];
             for (int i = 0; i < value.Data.Length; i++)
             {
                 uint offset = (uint)(this.dataStream.Position - start);
@@ -673,10 +668,7 @@ public int WriteNamedColor2TagDataEntry(IccNamedColor2TagDataEntry value)
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteParametricCurveTagDataEntry(IccParametricCurveTagDataEntry value)
-        {
-            return this.WriteParametricCurve(value.Curve);
-        }
+        public int WriteParametricCurveTagDataEntry(IccParametricCurveTagDataEntry value) => this.WriteParametricCurve(value.Curve);
 
         /// <summary>
         /// Writes a <see cref="IccProfileSequenceDescTagDataEntry"/>
@@ -793,20 +785,14 @@ public int WriteFix16ArrayTagDataEntry(IccFix16ArrayTagDataEntry value)
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteSignatureTagDataEntry(IccSignatureTagDataEntry value)
-        {
-            return this.WriteAsciiString(value.SignatureData, 4, false);
-        }
+        public int WriteSignatureTagDataEntry(IccSignatureTagDataEntry value) => this.WriteAsciiString(value.SignatureData, 4, false);
 
         /// <summary>
         /// Writes a <see cref="IccTextTagDataEntry"/>
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteTextTagDataEntry(IccTextTagDataEntry value)
-        {
-            return this.WriteAsciiString(value.Text);
-        }
+        public int WriteTextTagDataEntry(IccTextTagDataEntry value) => this.WriteAsciiString(value.Text);
 
         /// <summary>
         /// Writes a <see cref="IccUFix16ArrayTagDataEntry"/>
@@ -829,40 +815,28 @@ public int WriteUFix16ArrayTagDataEntry(IccUFix16ArrayTagDataEntry value)
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteUInt16ArrayTagDataEntry(IccUInt16ArrayTagDataEntry value)
-        {
-            return this.WriteArray(value.Data);
-        }
+        public int WriteUInt16ArrayTagDataEntry(IccUInt16ArrayTagDataEntry value) => this.WriteArray(value.Data);
 
         /// <summary>
         /// Writes a <see cref="IccUInt32ArrayTagDataEntry"/>
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteUInt32ArrayTagDataEntry(IccUInt32ArrayTagDataEntry value)
-        {
-            return this.WriteArray(value.Data);
-        }
+        public int WriteUInt32ArrayTagDataEntry(IccUInt32ArrayTagDataEntry value) => this.WriteArray(value.Data);
 
         /// <summary>
         /// Writes a <see cref="IccUInt64ArrayTagDataEntry"/>
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteUInt64ArrayTagDataEntry(IccUInt64ArrayTagDataEntry value)
-        {
-            return this.WriteArray(value.Data);
-        }
+        public int WriteUInt64ArrayTagDataEntry(IccUInt64ArrayTagDataEntry value) => this.WriteArray(value.Data);
 
         /// <summary>
         /// Writes a <see cref="IccUInt8ArrayTagDataEntry"/>
         /// </summary>
         /// <param name="value">The entry to write</param>
         /// <returns>The number of bytes written</returns>
-        public int WriteUInt8ArrayTagDataEntry(IccUInt8ArrayTagDataEntry value)
-        {
-            return this.WriteArray(value.Data);
-        }
+        public int WriteUInt8ArrayTagDataEntry(IccUInt8ArrayTagDataEntry value) => this.WriteArray(value.Data);
 
         /// <summary>
         /// Writes a <see cref="IccViewingConditionsTagDataEntry"/>

src/ImageSharp/MetaData/Profiles/ICC/IccWriter.cs

@@ -70,6 +70,7 @@ private void WriteTagTable(IccDataWriter writer, IccTagTableEntry[] table)
 
         private IccTagTableEntry[] WriteTagData(IccDataWriter writer, IccTagDataEntry[] entries)
         {
+            // TODO: Investigate cost of Linq GroupBy
             IEnumerable<IGrouping<IccTagDataEntry, IccTagDataEntry>> grouped = entries.GroupBy(t => t);
 
             // (Header size) + (entry count) + (nr of entries) * (size of table entry)

src/ImageSharp/MetaData/Profiles/ICC/MultiProcessElements/IccCurveSetProcessElement.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Linq;
 
 namespace SixLabors.ImageSharp.Metadata.Profiles.Icc
 {
@@ -17,9 +16,7 @@ internal sealed class IccCurveSetProcessElement : IccMultiProcessElement, IEquat
         /// <param name="curves">An array with one dimensional curves</param>
         public IccCurveSetProcessElement(IccOneDimensionalCurve[] curves)
             : base(IccMultiProcessElementSignature.CurveSet, curves?.Length ?? 1, curves?.Length ?? 1)
-        {
-            this.Curves = curves ?? throw new ArgumentNullException(nameof(curves));
-        }
+            => this.Curves = curves ?? throw new ArgumentNullException(nameof(curves));
 
         /// <summary>
         /// Gets an array of one dimensional curves
@@ -31,16 +28,13 @@ public override bool Equals(IccMultiProcessElement other)
         {
             if (base.Equals(other) && other is IccCurveSetProcessElement element)
             {
-                return this.Curves.SequenceEqual(element.Curves);
+                return this.Curves.AsSpan().SequenceEqual(element.Curves);
             }
 
             return false;
         }
 
         /// <inheritdoc />
-        public bool Equals(IccCurveSetProcessElement other)
-        {
-            return this.Equals((IccMultiProcessElement)other);
-        }
+        public bool Equals(IccCurveSetProcessElement other) => this.Equals((IccMultiProcessElement)other);
     }
 }