ImageSharp/tests/ImageSharp.Tests/Processing/Processors/Binarization/DitherTests.cs

// Copyright (c) Six Labors and contributors.
// Licensed under the Apache License, Version 2.0.

using SixLabors.ImageSharp.Dithering;
using SixLabors.ImageSharp.Dithering.Ordered;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;

using SixLabors.Primitives;
using Xunit;
// ReSharper disable InconsistentNaming

namespace SixLabors.ImageSharp.Tests.Processing.Processors.Binarization
{
    using System.Linq;

    public class DitherTests : FileTestBase
    {
        public static readonly string[] CommonTestImages =
            {
                TestImages.Png.CalliphoraPartial, TestImages.Png.Bike
            };

        public static readonly TheoryData<string, IOrderedDither> Ditherers = new TheoryData<string, IOrderedDither>
        {
            { "Ordered", new Ordered() },
            { "Bayer", new Bayer() }
        };

        public static readonly TheoryData<string, IErrorDiffuser> ErrorDiffusers = new TheoryData<string, IErrorDiffuser>
        {
            { "Atkinson", new Atkinson() },
            { "Burks", new Burks() },
            { "FloydSteinberg", new FloydSteinberg() },
            { "JarvisJudiceNinke", new JarvisJudiceNinke() },
            { "Sierra2", new Sierra2() },
            { "Sierra3", new Sierra3() },
            { "SierraLite", new SierraLite() },
            { "Stucki", new Stucki() },
        };


        private static IOrderedDither DefaultDitherer => new Ordered();

        private static IErrorDiffuser DefaultErrorDiffuser => new Atkinson();

        [Theory]
        [WithFileCollection(nameof(CommonTestImages), nameof(Ditherers), DefaultPixelType)]
        [WithTestPatternImages(nameof(Ditherers), 100, 100, DefaultPixelType)]
        public void DitherFilter_WorksWithAllDitherers<TPixel>(TestImageProvider<TPixel> provider, string name, IOrderedDither ditherer)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> image = provider.GetImage())
            {
                image.Mutate(x => x.Dither(ditherer));
                image.DebugSave(provider, name);
            }
        }

        [Theory]
        [WithFileCollection(nameof(CommonTestImages), nameof(ErrorDiffusers), DefaultPixelType)]
        [WithTestPatternImages(nameof(ErrorDiffusers), 100, 100, DefaultPixelType)]
        public void DiffusionFilter_WorksWithAllErrorDiffusers<TPixel>(TestImageProvider<TPixel> provider, string name, IErrorDiffuser diffuser)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> image = provider.GetImage())
            {
                image.Mutate(x => x.Dither(diffuser, .5F));
                image.DebugSave(provider, name);
            }
        }

        [Theory]
        [WithFile(TestImages.Png.Bike, CommonNonDefaultPixelTypes)]
        public void DitherFilter_ShouldNotDependOnSinglePixelType<TPixel>(TestImageProvider<TPixel> provider)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> image = provider.GetImage())
            {
                image.Mutate(x => x.Dither(DefaultDitherer));
                image.DebugSave(provider);
            }
        }
        
        [Theory]
        [WithFile(TestImages.Png.Bike, CommonNonDefaultPixelTypes)]
        public void DiffusionFilter_ShouldNotDependOnSinglePixelType<TPixel>(TestImageProvider<TPixel> provider)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> image = provider.GetImage())
            {
                image.Mutate(x => x.Dither(DefaultErrorDiffuser, 0.5f));
                image.DebugSave(provider);
            }
        }

        [Theory]
        [WithFile(TestImages.Png.CalliphoraPartial, DefaultPixelType)]
        public void ApplyDitherFilterInBox<TPixel>(TestImageProvider<TPixel> provider)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> source = provider.GetImage())
            using (Image<TPixel> image = source.Clone())
            {
                var bounds = new Rectangle(10, 10, image.Width / 2, image.Height / 2);

                image.Mutate(x => x.Dither(DefaultDitherer, bounds));
                image.DebugSave(provider);

                ImageComparer.Tolerant().EnsureProcessorChangesAreConstrained(source, image, bounds);
            }
        }

        // TODO: Does not work because of a bug! Fix it!
        [Theory(Skip = "TODO: Does not work because of a bug! Fix it!")]
        [WithFile(TestImages.Png.CalliphoraPartial, DefaultPixelType)]
        public void ApplyDiffusionFilterInBox<TPixel>(TestImageProvider<TPixel> provider)
            where TPixel : struct, IPixel<TPixel>
        {
            using (Image<TPixel> source = provider.GetImage())
            using (Image<TPixel> image = source.Clone())
            {
                var bounds = new Rectangle(10, 10, image.Width / 2, image.Height / 2);

                image.Mutate(x => x.Dither(DefaultErrorDiffuser, .5F, bounds));
                image.DebugSave(provider);

                ImageComparer.Tolerant().EnsureProcessorChangesAreConstrained(source, image, bounds);
            }
        }
    }
}