243 lines
9.1 KiB
C#
243 lines
9.1 KiB
C#
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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using MediaBrowser.Model.Drawing;
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using MediaBrowser.Model.IO;
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using Microsoft.Extensions.Logging;
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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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/// <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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}.ToArray();
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private static readonly int MaxMagicBytesLength = ImageFormatDecoders.Select(i => i.Key.Length).OrderByDescending(i => i).First();
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private static string[] SupportedExtensions = new string[] { ".jpg", ".jpeg", ".png", ".gif" };
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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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if (string.IsNullOrEmpty(path))
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{
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throw new ArgumentNullException(nameof(path));
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}
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string extension = Path.GetExtension(path).ToLower();
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if (!SupportedExtensions.Contains(extension))
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{
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throw new ArgumentException("ImageHeader doesn't support " + extension);
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}
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using (var fs = fileSystem.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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/// <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="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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for (var i = 0; i < MaxMagicBytesLength; i += 1)
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{
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magicBytes[i] = binaryReader.ReadByte();
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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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throw new ArgumentException(ErrorMessage, nameof(binaryReader));
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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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return true;
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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(this BinaryReader binaryReader)
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{
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var bytes = new byte[sizeof(short)];
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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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/// <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(this 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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/// <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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/// <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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/// <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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/// <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="ArgumentException"></exception>
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private static ImageSize DecodeJfif(BinaryReader binaryReader)
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{
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// A JPEG image consists of a sequence of segments,
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// each beginning with a marker, each of which begins with a 0xFF byte
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// followed by a byte indicating what kind of marker it is.
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// Source: https://en.wikipedia.org/wiki/JPEG#Syntax_and_structure
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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 = binaryReader.ReadLittleEndianInt16();
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// SOF0: Indicates that this is a baseline DCT-based JPEG,
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// and specifies the width, height, number of components, and component subsampling
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// SOF2: Indicates that this is a progressive DCT-based JPEG,
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// and specifies the width, height, number of components, and component subsampling
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if (marker == 0xc0 || marker == 0xc2)
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{
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// https://help.accusoft.com/ImageGear/v18.2/Windows/ActiveX/IGAX-10-12.html
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binaryReader.ReadByte(); // We don't care about the first byte
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int height = binaryReader.ReadLittleEndianInt16();
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int width = binaryReader.ReadLittleEndianInt16();
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return new ImageSize(width, height);
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}
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if (chunkLength < 0)
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{
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ushort 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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throw new ArgumentException(ErrorMessage);
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}
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}
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}
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