Added Png filter tests

tests/ImageSharp.Tests/Formats/Png/PngFilterTests.cs

@@ -0,0 +1,270 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+// Uncomment this to turn unit tests into benchmarks:
+// #define BENCHMARKING
+using System;
+
+using SixLabors.ImageSharp.Formats.Png;
+using SixLabors.ImageSharp.Formats.Png.Filters;
+using SixLabors.ImageSharp.Tests.Formats.Png.Utils;
+using SixLabors.ImageSharp.Tests.TestUtilities;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Png
+{
+    [Trait("Format", "Png")]
+    public partial class PngFilterTests : MeasureFixture
+    {
+#if BENCHMARKING
+        public const int Times = 1000000;
+#else
+        public const int Times = 1;
+#endif
+
+        public PngFilterTests(ITestOutputHelper output)
+            : base(output)
+        {
+        }
+
+        public const int Size = 64;
+
+        [Fact]
+        public void Average()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Average, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.DisableSIMD);
+        }
+
+        [Fact]
+        public void AverageSse2()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Average, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll | HwIntrinsics.DisableAVX2 | HwIntrinsics.DisableSSSE3);
+        }
+
+        [Fact]
+        public void AverageSsse3()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Average, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll | HwIntrinsics.DisableAVX2);
+        }
+
+        [Fact]
+        public void AverageAvx2()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Average, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll);
+        }
+
+        [Fact]
+        public void Paeth()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Paeth, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.DisableSIMD);
+        }
+
+        [Fact]
+        public void PaethSimd()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Paeth, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll);
+        }
+
+        [Fact]
+        public void Up()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Up, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.DisableSIMD);
+        }
+
+        [Fact]
+        public void UpSimd()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Up, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll);
+        }
+
+        [Fact]
+        public void Sub()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Sub, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.DisableSIMD);
+        }
+
+        [Fact]
+        public void SubSimd()
+        {
+            static void RunTest()
+            {
+                var data = new TestData(PngFilterMethod.Sub, Size);
+                data.TestFilter();
+            }
+
+            FeatureTestRunner.RunWithHwIntrinsicsFeature(
+                RunTest,
+                HwIntrinsics.AllowAll);
+        }
+
+        public class TestData
+        {
+            private readonly PngFilterMethod filter;
+            private readonly int bpp;
+            private readonly byte[] previousScanline;
+            private readonly byte[] scanline;
+            private readonly byte[] expectedResult;
+            private readonly int expectedSum;
+            private readonly byte[] resultBuffer;
+
+            public TestData(PngFilterMethod filter, int size, int bpp = 4)
+            {
+                this.filter = filter;
+                this.bpp = bpp;
+                this.previousScanline = new byte[size * size * bpp];
+                this.scanline = new byte[size * size * bpp];
+                this.expectedResult = new byte[1 + (size * size * bpp)];
+                this.resultBuffer = new byte[1 + (size * size * bpp)];
+
+                var rng = new Random(12345678);
+                byte[] tmp = new byte[6];
+                for (int i = 0; i < this.previousScanline.Length; i += bpp)
+                {
+                    rng.NextBytes(tmp);
+
+                    this.previousScanline[i + 0] = tmp[0];
+                    this.previousScanline[i + 1] = tmp[1];
+                    this.previousScanline[i + 2] = tmp[2];
+                    this.previousScanline[i + 3] = 255;
+
+                    this.scanline[i + 0] = tmp[3];
+                    this.scanline[i + 1] = tmp[4];
+                    this.scanline[i + 2] = tmp[5];
+                    this.scanline[i + 3] = 255;
+                }
+
+                switch (this.filter)
+                {
+                    case PngFilterMethod.Sub:
+                        ReferenceImplementations.EncodeSubFilter(
+                            this.scanline, this.expectedResult, this.bpp, out this.expectedSum);
+                        break;
+
+                    case PngFilterMethod.Up:
+                        ReferenceImplementations.EncodeUpFilter(
+                            this.previousScanline, this.scanline, this.expectedResult, out this.expectedSum);
+                        break;
+
+                    case PngFilterMethod.Average:
+                        ReferenceImplementations.EncodeAverageFilter(
+                            this.previousScanline, this.scanline, this.expectedResult, this.bpp, out this.expectedSum);
+                        break;
+
+                    case PngFilterMethod.Paeth:
+                        ReferenceImplementations.EncodePaethFilter(
+                            this.previousScanline, this.scanline, this.expectedResult, this.bpp, out this.expectedSum);
+                        break;
+
+                    case PngFilterMethod.None:
+                    case PngFilterMethod.Adaptive:
+                    default:
+                        throw new InvalidOperationException();
+                }
+            }
+
+            public void TestFilter()
+            {
+                int sum;
+                switch (this.filter)
+                {
+                    case PngFilterMethod.Sub:
+                        SubFilter.Encode(this.scanline, this.resultBuffer, this.bpp, out sum);
+                        break;
+
+                    case PngFilterMethod.Up:
+                        UpFilter.Encode(this.previousScanline, this.scanline, this.resultBuffer, out sum);
+                        break;
+
+                    case PngFilterMethod.Average:
+                        AverageFilter.Encode(this.previousScanline, this.scanline, this.resultBuffer, this.bpp, out sum);
+                        break;
+
+                    case PngFilterMethod.Paeth:
+                        PaethFilter.Encode(this.previousScanline, this.scanline, this.resultBuffer, this.bpp, out sum);
+                        break;
+
+                    case PngFilterMethod.None:
+                    case PngFilterMethod.Adaptive:
+                    default:
+                        throw new InvalidOperationException();
+                }
+
+                Assert.Equal(this.expectedSum, sum);
+                Assert.Equal(this.expectedResult, this.resultBuffer);
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Png/ReferenceImplementations.cs

@@ -0,0 +1,229 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// ReSharper disable InconsistentNaming
+namespace SixLabors.ImageSharp.Tests.Formats.Png.Utils
+{
+    /// <summary>
+    /// This class contains reference implementations to produce verification data for unit tests
+    /// </summary>
+    internal static partial class ReferenceImplementations
+    {
+        /// <summary>
+        /// Encodes the scanline
+        /// </summary>
+        /// <param name="scanline">The scanline to encode</param>
+        /// <param name="previousScanline">The previous scanline.</param>
+        /// <param name="result">The filtered scanline result.</param>
+        /// <param name="bytesPerPixel">The bytes per pixel.</param>
+        /// <param name="sum">The sum of the total variance of the filtered row</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EncodePaethFilter(Span<byte> scanline, Span<byte> previousScanline, Span<byte> result, int bytesPerPixel, out int sum)
+        {
+            DebugGuard.MustBeSameSized(scanline, previousScanline, nameof(scanline));
+            DebugGuard.MustBeSizedAtLeast(result, scanline, nameof(result));
+
+            ref byte scanBaseRef = ref MemoryMarshal.GetReference(scanline);
+            ref byte prevBaseRef = ref MemoryMarshal.GetReference(previousScanline);
+            ref byte resultBaseRef = ref MemoryMarshal.GetReference(result);
+            sum = 0;
+
+            // Paeth(x) = Raw(x) - PaethPredictor(Raw(x-bpp), Prior(x), Prior(x - bpp))
+            resultBaseRef = 4;
+
+            int x = 0;
+            for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte above = Unsafe.Add(ref prevBaseRef, x);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - PaethPredictor(0, above, 0));
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte left = Unsafe.Add(ref scanBaseRef, xLeft);
+                byte above = Unsafe.Add(ref prevBaseRef, x);
+                byte upperLeft = Unsafe.Add(ref prevBaseRef, xLeft);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - PaethPredictor(left, above, upperLeft));
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            sum -= 4;
+        }
+
+        /// <summary>
+        /// Encodes the scanline
+        /// </summary>
+        /// <param name="scanline">The scanline to encode</param>
+        /// <param name="result">The filtered scanline result.</param>
+        /// <param name="bytesPerPixel">The bytes per pixel.</param>
+        /// <param name="sum">The sum of the total variance of the filtered row</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EncodeSubFilter(Span<byte> scanline, Span<byte> result, int bytesPerPixel, out int sum)
+        {
+            DebugGuard.MustBeSizedAtLeast(result, scanline, nameof(result));
+
+            ref byte scanBaseRef = ref MemoryMarshal.GetReference(scanline);
+            ref byte resultBaseRef = ref MemoryMarshal.GetReference(result);
+            sum = 0;
+
+            // Sub(x) = Raw(x) - Raw(x-bpp)
+            resultBaseRef = 1;
+
+            int x = 0;
+            for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = scan;
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte prev = Unsafe.Add(ref scanBaseRef, xLeft);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - prev);
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            sum -= 1;
+        }
+
+        /// <summary>
+        /// Encodes the scanline
+        /// </summary>
+        /// <param name="scanline">The scanline to encode</param>
+        /// <param name="previousScanline">The previous scanline.</param>
+        /// <param name="result">The filtered scanline result.</param>
+        /// <param name="sum">The sum of the total variance of the filtered row</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EncodeUpFilter(Span<byte> scanline, Span<byte> previousScanline, Span<byte> result, out int sum)
+        {
+            DebugGuard.MustBeSameSized(scanline, previousScanline, nameof(scanline));
+            DebugGuard.MustBeSizedAtLeast(result, scanline, nameof(result));
+
+            ref byte scanBaseRef = ref MemoryMarshal.GetReference(scanline);
+            ref byte prevBaseRef = ref MemoryMarshal.GetReference(previousScanline);
+            ref byte resultBaseRef = ref MemoryMarshal.GetReference(result);
+            sum = 0;
+
+            // Up(x) = Raw(x) - Prior(x)
+            resultBaseRef = 2;
+
+            int x = 0;
+
+            for (; x < scanline.Length; /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte above = Unsafe.Add(ref prevBaseRef, x);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - above);
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            sum -= 2;
+        }
+
+        /// <summary>
+        /// Encodes the scanline
+        /// </summary>
+        /// <param name="scanline">The scanline to encode</param>
+        /// <param name="previousScanline">The previous scanline.</param>
+        /// <param name="result">The filtered scanline result.</param>
+        /// <param name="bytesPerPixel">The bytes per pixel.</param>
+        /// <param name="sum">The sum of the total variance of the filtered row</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EncodeAverageFilter(Span<byte> scanline, Span<byte> previousScanline, Span<byte> result, int bytesPerPixel, out int sum)
+        {
+            DebugGuard.MustBeSameSized(scanline, previousScanline, nameof(scanline));
+            DebugGuard.MustBeSizedAtLeast(result, scanline, nameof(result));
+
+            ref byte scanBaseRef = ref MemoryMarshal.GetReference(scanline);
+            ref byte prevBaseRef = ref MemoryMarshal.GetReference(previousScanline);
+            ref byte resultBaseRef = ref MemoryMarshal.GetReference(result);
+            sum = 0;
+
+            // Average(x) = Raw(x) - floor((Raw(x-bpp)+Prior(x))/2)
+            resultBaseRef = 3;
+
+            int x = 0;
+            for (; x < bytesPerPixel; /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte above = Unsafe.Add(ref prevBaseRef, x);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - (above >> 1));
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            for (int xLeft = x - bytesPerPixel; x < scanline.Length; ++xLeft /* Note: ++x happens in the body to avoid one add operation */)
+            {
+                byte scan = Unsafe.Add(ref scanBaseRef, x);
+                byte left = Unsafe.Add(ref scanBaseRef, xLeft);
+                byte above = Unsafe.Add(ref prevBaseRef, x);
+                ++x;
+                ref byte res = ref Unsafe.Add(ref resultBaseRef, x);
+                res = (byte)(scan - Average(left, above));
+                sum += Numerics.Abs(unchecked((sbyte)res));
+            }
+
+            sum -= 3;
+        }
+
+        /// <summary>
+        /// Calculates the average value of two bytes
+        /// </summary>
+        /// <param name="left">The left byte</param>
+        /// <param name="above">The above byte</param>
+        /// <returns>The <see cref="int"/></returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int Average(byte left, byte above) => (left + above) >> 1;
+
+        /// <summary>
+        /// Computes a simple linear function of the three neighboring pixels (left, above, upper left), then chooses
+        /// as predictor the neighboring pixel closest to the computed value.
+        /// </summary>
+        /// <param name="left">The left neighbor pixel.</param>
+        /// <param name="above">The above neighbor pixel.</param>
+        /// <param name="upperLeft">The upper left neighbor pixel.</param>
+        /// <returns>
+        /// The <see cref="byte"/>.
+        /// </returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static byte PaethPredictor(byte left, byte above, byte upperLeft)
+        {
+            int p = left + above - upperLeft;
+            int pa = Numerics.Abs(p - left);
+            int pb = Numerics.Abs(p - above);
+            int pc = Numerics.Abs(p - upperLeft);
+
+            if (pa <= pb && pa <= pc)
+            {
+                return left;
+            }
+
+            if (pb <= pc)
+            {
+                return above;
+            }
+
+            return upperLeft;
+        }
+    }
+}