ImageSharp/src/ImageSharp/Formats/Jpeg/JpegEncoder.cs

// <copyright file="JpegEncoder.cs" company="James Jackson-South">
// Copyright (c) James Jackson-South and contributors.
// Licensed under the Apache License, Version 2.0.
// </copyright>

namespace ImageSharp.Formats
{
    using System;
    using System.Collections.Generic;
    using System.IO;

    using ImageSharp.PixelFormats;

    /// <summary>
    /// Encoder for writing the data image to a stream in jpeg format.
    /// </summary>
    public class JpegEncoder : IImageEncoder
    {
        /// <summary>
        /// Gets or sets a value indicating whether the metadata should be ignored when the image is being decoded.
        /// </summary>
        public bool IgnoreMetadata { get; set; }

        /// <summary>
        /// Gets or sets the quality, that will be used to encode the image. Quality
        /// index must be between 0 and 100 (compression from max to min).
        /// </summary>
        /// <value>The quality of the jpg image from 0 to 100.</value>
        public int Quality { get; set; }

        /// <summary>
        /// Gets or sets the subsample ration, that will be used to encode the image.
        /// </summary>
        /// <value>The subsample ratio of the jpg image.</value>
        public JpegSubsample? Subsample { get; set; }

        /// <summary>
        /// Encodes the image to the specified stream from the <see cref="Image{TPixel}"/>.
        /// </summary>
        /// <typeparam name="TPixel">The pixel format.</typeparam>
        /// <param name="image">The <see cref="Image{TPixel}"/> to encode from.</param>
        /// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
        public void Encode<TPixel>(Image<TPixel> image, Stream stream)
        where TPixel : struct, IPixel<TPixel>
        {
            JpegEncoderCore encoder = new JpegEncoderCore();

            var quality = this.Quality;
            if (quality == 0)
            {
                quality = 75;
            }

            encoder.Quality = quality;
            encoder.Subsample = this.Subsample ?? (quality >= 91 ? JpegSubsample.Ratio444 : JpegSubsample.Ratio420);

            encoder.IgnoreMetadata = this.IgnoreMetadata;

            encoder.Encode(image, stream);
        }
    }
}