ImageSharp/src/ImageProcessor/Imaging/Formats/FormatUtilities.cs

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="FormatUtilities.cs" company="James South">
//   Copyright (c) James South.
//   Licensed under the Apache License, Version 2.0.
// </copyright>
// <summary>
//   Utility methods for working with supported image formats.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

namespace ImageProcessor.Imaging.Formats
{
    using System;
    using System.Collections.Concurrent;
    using System.Collections.Generic;
    using System.Drawing;
    using System.Drawing.Imaging;
    using System.IO;
    using System.Linq;
    using System.Reflection;
    using System.Threading.Tasks;

    using ImageProcessor.Configuration;

    /// <summary>
    /// Utility methods for working with supported image formats.
    /// </summary>
    public static class FormatUtilities
    {
        /// <summary>
        /// Gets the correct <see cref="ISupportedImageFormat"/> from the given stream.
        /// <see href="http://stackoverflow.com/questions/55869/determine-file-type-of-an-image"/>
        /// </summary>
        /// <param name="stream">
        /// The <see cref="System.IO.Stream"/> to read from.
        /// </param>
        /// <returns>
        /// The <see cref="ISupportedImageFormat"/>.
        /// </returns>
        public static ISupportedImageFormat GetFormat(Stream stream)
        {
            // Reset the position of the stream to ensure we're reading the correct part.
            stream.Position = 0;

            IEnumerable<ISupportedImageFormat> supportedImageFormats =
                ImageProcessorBootstrapper.Instance.SupportedImageFormats;

            byte[] buffer = new byte[4];
            stream.Read(buffer, 0, buffer.Length);

            foreach (ISupportedImageFormat supportedImageFormat in supportedImageFormats)
            {
                byte[][] headers = supportedImageFormat.FileHeaders;

                // ReSharper disable once LoopCanBeConvertedToQuery
                foreach (byte[] header in headers)
                {
                    if (header.SequenceEqual(buffer.Take(header.Length)))
                    {
                        stream.Position = 0;

                        // Return a new instance as we want to use instance properties.
                        return Activator.CreateInstance(supportedImageFormat.GetType()) as ISupportedImageFormat;
                    }
                }
            }

            stream.Position = 0;
            return null;
        }

        /// <summary>
        /// Returns a value indicating whether the given image is indexed.
        /// </summary>
        /// <param name="image">
        /// The <see cref="System.Drawing.Image"/> to test.
        /// </param>
        /// <returns>
        /// The true if the image is indexed; otherwise, false.
        /// </returns>
        public static bool IsIndexed(Image image)
        {
            // Test value of flags using bitwise AND.
            // ReSharper disable once BitwiseOperatorOnEnumWithoutFlags
            return (image.PixelFormat & PixelFormat.Indexed) != 0;
        }

        /// <summary>
        /// Returns the color count from the palette of the given image.
        /// </summary>
        /// <param name="image">
        /// The <see cref="System.Drawing.Image"/> to get the colors from.
        /// </param>
        /// <returns>
        /// The <see cref="int"/> representing the color count.
        /// </returns>
        public static int GetColorCount(Image image)
        {
            ConcurrentDictionary<Color, Color> colors = new ConcurrentDictionary<Color, Color>();
            int width = image.Width;
            int height = image.Height;

            using (FastBitmap fastBitmap = new FastBitmap(image))
            {
                Parallel.For(
                    0,
                    height,
                    y =>
                    {
                        for (int x = 0; x < width; x++)
                        {
                            // ReSharper disable once AccessToDisposedClosure
                            Color color = fastBitmap.GetPixel(x, y);
                            colors.TryAdd(color, color);
                        }
                    });
            }

            int count = colors.Count;
            colors.Clear();
            return count;
        }

        /// <summary>
        /// Returns a value indicating whether the given image is indexed.
        /// </summary>
        /// <param name="image">
        /// The <see cref="System.Drawing.Image"/> to test.
        /// </param>
        /// <returns>
        /// The true if the image is animated; otherwise, false.
        /// </returns>
        public static bool IsAnimated(Image image)
        {
            return ImageAnimator.CanAnimate(image);
        }

        /// <summary>
        /// Returns an instance of EncodingParameters for jpeg compression. 
        /// </summary>
        /// <param name="quality">The quality to return the image at.</param>
        /// <returns>The encodingParameters for jpeg compression. </returns>
        public static EncoderParameters GetEncodingParameters(int quality)
        {
            EncoderParameters encoderParameters = null;
            try
            {
                // Create a series of encoder parameters.
                encoderParameters = new EncoderParameters(1);

                // Set the quality.
                encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);
            }
            catch
            {
                if (encoderParameters != null)
                {
                    encoderParameters.Dispose();
                }
            }

            return encoderParameters;
        }

        /// <summary>
        /// Uses reflection to allow the creation of an instance of <see cref="PropertyItem"/>.
        /// </summary>
        /// <returns>
        /// The <see cref="PropertyItem"/>.
        /// </returns>
        public static PropertyItem CreatePropertyItem()
        {
            Type type = typeof(PropertyItem);
            ConstructorInfo constructor = type.GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public, null, new Type[] { }, null);

            return (PropertyItem)constructor.Invoke(null);
        }
    }
}