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+using MediaBrowser.Common.IO;
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+using MediaBrowser.Model.Drawing;
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+using MediaBrowser.Model.Logging;
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+using System;
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+using System.Collections.Generic;
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+using System.IO;
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+using System.Linq;
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+
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+namespace Emby.Drawing.Common
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+{
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+ /// <summary>
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+ /// Taken from http://stackoverflow.com/questions/111345/getting-image-dimensions-without-reading-the-entire-file/111349
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+ /// http://www.codeproject.com/Articles/35978/Reading-Image-Headers-to-Get-Width-and-Height
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+ /// Minor improvements including supporting unsigned 16-bit integers when decoding Jfif and added logic
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+ /// to load the image using new Bitmap if reading the headers fails
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+ /// </summary>
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+ public static class ImageHeader
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+ {
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+ /// <summary>
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+ /// The error message
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+ /// </summary>
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+ const string ErrorMessage = "Could not recognize image format.";
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+
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+ /// <summary>
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+ /// The image format decoders
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+ /// </summary>
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+ private static readonly KeyValuePair<byte[], Func<BinaryReader, ImageSize>>[] ImageFormatDecoders = new Dictionary<byte[], Func<BinaryReader, ImageSize>>
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+ {
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+ { new byte[] { 0x42, 0x4D }, DecodeBitmap },
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+ { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 }, DecodeGif },
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+ { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 }, DecodeGif },
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+ { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }, DecodePng },
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+ { new byte[] { 0xff, 0xd8 }, DecodeJfif }
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+
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+ }.ToArray();
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+
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+ private static readonly int MaxMagicBytesLength = ImageFormatDecoders.Select(i => i.Key.Length).OrderByDescending(i => i).First();
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+
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+ /// <summary>
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+ /// Gets the dimensions of an image.
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+ /// </summary>
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+ /// <param name="path">The path of the image to get the dimensions of.</param>
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+ /// <param name="logger">The logger.</param>
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+ /// <param name="fileSystem">The file system.</param>
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+ /// <returns>The dimensions of the specified image.</returns>
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+ /// <exception cref="ArgumentException">The image was of an unrecognised format.</exception>
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+ public static ImageSize GetDimensions(string path, ILogger logger, IFileSystem fileSystem)
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+ {
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+ using (var fs = File.OpenRead(path))
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+ {
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+ using (var binaryReader = new BinaryReader(fs))
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+ {
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+ return GetDimensions(binaryReader);
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+ }
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+ }
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+ }
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+
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+ /// <summary>
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+ /// Gets the dimensions of an image.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>Size.</returns>
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+ /// <exception cref="System.ArgumentException">binaryReader</exception>
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+ /// <exception cref="ArgumentException">The image was of an unrecognized format.</exception>
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+ private static ImageSize GetDimensions(BinaryReader binaryReader)
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+ {
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+ var magicBytes = new byte[MaxMagicBytesLength];
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+
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+ for (var i = 0; i < MaxMagicBytesLength; i += 1)
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+ {
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+ magicBytes[i] = binaryReader.ReadByte();
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+
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+ foreach (var kvPair in ImageFormatDecoders)
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+ {
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+ if (StartsWith(magicBytes, kvPair.Key))
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+ {
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+ return kvPair.Value(binaryReader);
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+ }
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+ }
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+ }
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+
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+ throw new ArgumentException(ErrorMessage, "binaryReader");
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+ }
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+
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+ /// <summary>
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+ /// Startses the with.
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+ /// </summary>
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+ /// <param name="thisBytes">The this bytes.</param>
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+ /// <param name="thatBytes">The that bytes.</param>
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+ /// <returns><c>true</c> if XXXX, <c>false</c> otherwise</returns>
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+ private static bool StartsWith(byte[] thisBytes, byte[] thatBytes)
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+ {
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+ for (int i = 0; i < thatBytes.Length; i += 1)
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+ {
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+ if (thisBytes[i] != thatBytes[i])
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+ {
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+ return false;
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+ }
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+ }
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+
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+ return true;
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+ }
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+
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+ /// <summary>
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+ /// Reads the little endian int16.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>System.Int16.</returns>
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+ private static short ReadLittleEndianInt16(BinaryReader binaryReader)
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+ {
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+ var bytes = new byte[sizeof(short)];
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+
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+ for (int i = 0; i < sizeof(short); i += 1)
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+ {
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+ bytes[sizeof(short) - 1 - i] = binaryReader.ReadByte();
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+ }
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+ return BitConverter.ToInt16(bytes, 0);
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+ }
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+
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+ /// <summary>
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+ /// Reads the little endian int32.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>System.Int32.</returns>
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+ private static int ReadLittleEndianInt32(BinaryReader binaryReader)
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+ {
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+ var bytes = new byte[sizeof(int)];
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+ for (int i = 0; i < sizeof(int); i += 1)
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+ {
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+ bytes[sizeof(int) - 1 - i] = binaryReader.ReadByte();
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+ }
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+ return BitConverter.ToInt32(bytes, 0);
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+ }
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+
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+ /// <summary>
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+ /// Decodes the bitmap.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>Size.</returns>
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+ private static ImageSize DecodeBitmap(BinaryReader binaryReader)
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+ {
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+ binaryReader.ReadBytes(16);
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+ int width = binaryReader.ReadInt32();
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+ int height = binaryReader.ReadInt32();
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+ return new ImageSize
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+ {
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+ Width = width,
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+ Height = height
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+ };
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+ }
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+
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+ /// <summary>
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+ /// Decodes the GIF.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>Size.</returns>
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+ private static ImageSize DecodeGif(BinaryReader binaryReader)
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+ {
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+ int width = binaryReader.ReadInt16();
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+ int height = binaryReader.ReadInt16();
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+ return new ImageSize
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+ {
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+ Width = width,
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+ Height = height
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+ };
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+ }
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+
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+ /// <summary>
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+ /// Decodes the PNG.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>Size.</returns>
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+ private static ImageSize DecodePng(BinaryReader binaryReader)
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+ {
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+ binaryReader.ReadBytes(8);
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+ int width = ReadLittleEndianInt32(binaryReader);
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+ int height = ReadLittleEndianInt32(binaryReader);
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+ return new ImageSize
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+ {
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+ Width = width,
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+ Height = height
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+ };
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+ }
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+
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+ /// <summary>
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+ /// Decodes the jfif.
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+ /// </summary>
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+ /// <param name="binaryReader">The binary reader.</param>
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+ /// <returns>Size.</returns>
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+ /// <exception cref="System.ArgumentException"></exception>
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+ private static ImageSize DecodeJfif(BinaryReader binaryReader)
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+ {
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+ while (binaryReader.ReadByte() == 0xff)
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+ {
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+ byte marker = binaryReader.ReadByte();
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+ short chunkLength = ReadLittleEndianInt16(binaryReader);
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+ if (marker == 0xc0)
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+ {
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+ binaryReader.ReadByte();
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+ int height = ReadLittleEndianInt16(binaryReader);
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+ int width = ReadLittleEndianInt16(binaryReader);
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+ return new ImageSize
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+ {
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+ Width = width,
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+ Height = height
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+ };
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+ }
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+
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+ if (chunkLength < 0)
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+ {
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+ var uchunkLength = (ushort)chunkLength;
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+ binaryReader.ReadBytes(uchunkLength - 2);
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+ }
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+ else
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+ {
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+ binaryReader.ReadBytes(chunkLength - 2);
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+ }
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+ }
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+
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+ throw new ArgumentException(ErrorMessage);
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+ }
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+ }
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+}
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