ImageSharp/tests/ImageSharp.Tests/Formats/Jpg/QuantizationTests.cs

// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using SixLabors.ImageSharp.Formats.Jpeg.Components;
using JpegQuantization = SixLabors.ImageSharp.Formats.Jpeg.Components.Quantization;

namespace SixLabors.ImageSharp.Tests.Formats.Jpg;

[Trait("Format", "Jpg")]
public class QuantizationTests
{
    [Fact]
    public void QualityEstimationFromStandardEncoderTables_Luminance()
    {
        int firstIndex = JpegQuantization.QualityEstimationConfidenceLowerThreshold;
        int lastIndex = JpegQuantization.QualityEstimationConfidenceUpperThreshold;
        for (int quality = firstIndex; quality <= lastIndex; quality++)
        {
            Block8x8F table = JpegQuantization.ScaleLuminanceTable(quality);
            int estimatedQuality = JpegQuantization.EstimateLuminanceQuality(ref table);

            Assert.True(
                quality.Equals(estimatedQuality),
                $"Failed to estimate luminance quality for standard table at quality level {quality}");
        }
    }

    [Fact]
    public void QualityEstimationFromStandardEncoderTables_Chrominance()
    {
        int firstIndex = JpegQuantization.QualityEstimationConfidenceLowerThreshold;
        int lastIndex = JpegQuantization.QualityEstimationConfidenceUpperThreshold;
        for (int quality = firstIndex; quality <= lastIndex; quality++)
        {
            Block8x8F table = JpegQuantization.ScaleChrominanceTable(quality);
            int estimatedQuality = JpegQuantization.EstimateChrominanceQuality(ref table);

            Assert.True(
                quality.Equals(estimatedQuality),
                $"Failed to estimate chrominance quality for standard table at quality level {quality}");
        }
    }
}