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967 lines
37 KiB
967 lines
37 KiB
// <copyright file="PngDecoderCore.cs" company="James Jackson-South">
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// Copyright (c) James Jackson-South and contributors.
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// Licensed under the Apache License, Version 2.0.
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// </copyright>
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namespace ImageSharp.Formats
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{
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using System;
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using System.Buffers;
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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 System.Text;
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using static ComparableExtensions;
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/// <summary>
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/// Performs the png decoding operation.
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/// </summary>
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internal class PngDecoderCore
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{
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/// <summary>
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/// The dictionary of available color types.
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/// </summary>
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private static readonly Dictionary<int, byte[]> ColorTypes = new Dictionary<int, byte[]>();
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/// <summary>
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/// The amount to increment when processing each column per scanline for each interlaced pass
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/// </summary>
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private static readonly int[] Adam7ColumnIncrement = { 8, 8, 4, 4, 2, 2, 1 };
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/// <summary>
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/// The index to start at when processing each column per scanline for each interlaced pass
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/// </summary>
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private static readonly int[] Adam7FirstColumn = { 0, 4, 0, 2, 0, 1, 0 };
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/// <summary>
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/// The index to start at when processing each row per scanline for each interlaced pass
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/// </summary>
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private static readonly int[] Adam7FirstRow = { 0, 0, 4, 0, 2, 0, 1 };
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/// <summary>
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/// The amount to increment when processing each row per scanline for each interlaced pass
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/// </summary>
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private static readonly int[] Adam7RowIncrement = { 8, 8, 8, 4, 4, 2, 2 };
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/// <summary>
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/// Reusable buffer for reading chunk types.
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/// </summary>
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private readonly byte[] chunkTypeBuffer = new byte[4];
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/// <summary>
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/// Reusable buffer for reading chunk lengths.
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/// </summary>
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private readonly byte[] chunkLengthBuffer = new byte[4];
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/// <summary>
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/// Reusable buffer for reading crc values.
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/// </summary>
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private readonly byte[] crcBuffer = new byte[4];
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/// <summary>
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/// Reusable buffer for reading char arrays.
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/// </summary>
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private readonly char[] chars = new char[4];
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/// <summary>
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/// Reusable crc for validating chunks.
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/// </summary>
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private readonly Crc32 crc = new Crc32();
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/// <summary>
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/// The stream to decode from.
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/// </summary>
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private Stream currentStream;
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/// <summary>
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/// The png header.
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/// </summary>
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private PngHeader header;
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/// <summary>
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/// The number of bytes per pixel.
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/// </summary>
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private int bytesPerPixel;
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/// <summary>
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/// The number of bytes per sample
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/// </summary>
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private int bytesPerSample;
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/// <summary>
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/// The number of bytes per scanline
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/// </summary>
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private int bytesPerScanline;
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/// <summary>
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/// The palette containing color information for indexed png's
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/// </summary>
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private byte[] palette;
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/// <summary>
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/// The palette containing alpha channel color information for indexed png's
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/// </summary>
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private byte[] paletteAlpha;
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/// <summary>
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/// Initializes static members of the <see cref="PngDecoderCore"/> class.
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/// </summary>
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static PngDecoderCore()
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{
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ColorTypes.Add((int)PngColorType.Grayscale, new byte[] { 1, 2, 4, 8 });
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ColorTypes.Add((int)PngColorType.Rgb, new byte[] { 8 });
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ColorTypes.Add((int)PngColorType.Palette, new byte[] { 1, 2, 4, 8 });
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ColorTypes.Add((int)PngColorType.GrayscaleWithAlpha, new byte[] { 8 });
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ColorTypes.Add((int)PngColorType.RgbWithAlpha, new byte[] { 8 });
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}
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/// <summary>
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/// Gets or sets the png color type
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/// </summary>
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public PngColorType PngColorType { get; set; }
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/// <summary>
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/// Decodes the stream to the image.
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="image">The image to decode to.</param>
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/// <param name="stream">The stream containing image data. </param>
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/// <exception cref="ImageFormatException">
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/// Thrown if the stream does not contain and end chunk.
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/// </exception>
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/// <exception cref="System.ArgumentOutOfRangeException">
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/// Thrown if the image is larger than the maximum allowable size.
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/// </exception>
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public void Decode<TColor>(Image<TColor> image, Stream stream)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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Image<TColor> currentImage = image;
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this.currentStream = stream;
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this.currentStream.Skip(8);
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bool isEndChunkReached = false;
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using (MemoryStream dataStream = new MemoryStream())
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{
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PngChunk currentChunk;
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while ((currentChunk = this.ReadChunk()) != null)
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{
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if (isEndChunkReached)
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{
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throw new ImageFormatException("Image does not end with end chunk.");
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}
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try
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{
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switch (currentChunk.Type)
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{
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case PngChunkTypes.Header:
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this.ReadHeaderChunk(currentChunk.Data);
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this.ValidateHeader();
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break;
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case PngChunkTypes.Physical:
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this.ReadPhysicalChunk(currentImage, currentChunk.Data);
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break;
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case PngChunkTypes.Data:
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dataStream.Write(currentChunk.Data, 0, currentChunk.Length);
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break;
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case PngChunkTypes.Palette:
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byte[] pal = new byte[currentChunk.Length];
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Buffer.BlockCopy(currentChunk.Data, 0, pal, 0, currentChunk.Length);
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this.palette = pal;
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image.MetaData.Quality = pal.Length / 3;
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break;
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case PngChunkTypes.PaletteAlpha:
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byte[] alpha = new byte[currentChunk.Length];
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Buffer.BlockCopy(currentChunk.Data, 0, alpha, 0, currentChunk.Length);
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this.paletteAlpha = alpha;
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break;
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case PngChunkTypes.Text:
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this.ReadTextChunk(currentImage, currentChunk.Data, currentChunk.Length);
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break;
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case PngChunkTypes.End:
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isEndChunkReached = true;
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break;
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}
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}
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finally
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{
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// Data is rented in ReadChunkData()
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ArrayPool<byte>.Shared.Return(currentChunk.Data);
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}
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}
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if (this.header.Width > image.MaxWidth || this.header.Height > image.MaxHeight)
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{
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throw new ArgumentOutOfRangeException($"The input png '{this.header.Width}x{this.header.Height}' is bigger than the max allowed size '{image.MaxWidth}x{image.MaxHeight}'");
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}
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image.InitPixels(this.header.Width, this.header.Height);
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using (PixelAccessor<TColor> pixels = image.Lock())
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{
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this.ReadScanlines(dataStream, pixels);
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}
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}
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}
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/// <summary>
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/// Converts a byte array to a new array where each value in the original array is represented by the specified number of bits.
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/// </summary>
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/// <param name="source">The bytes to convert from. Cannot be null.</param>
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/// <param name="bytesPerScanline">The number of bytes per scanline</param>
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/// <param name="bits">The number of bits per value.</param>
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/// <returns>The resulting <see cref="T:byte[]"/> array. Is never null.</returns>
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/// <exception cref="System.ArgumentNullException"><paramref name="source"/> is null.</exception>
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/// <exception cref="System.ArgumentException"><paramref name="bits"/> is less than or equals than zero.</exception>
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private static byte[] ToArrayByBitsLength(byte[] source, int bytesPerScanline, int bits)
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{
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Guard.NotNull(source, nameof(source));
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Guard.MustBeGreaterThan(bits, 0, nameof(bits));
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byte[] result;
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if (bits < 8)
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{
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result = new byte[bytesPerScanline * 8 / bits];
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int mask = 0xFF >> (8 - bits);
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int resultOffset = 0;
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// ReSharper disable once ForCanBeConvertedToForeach
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// First byte is the marker so skip.
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for (int i = 1; i < bytesPerScanline; i++)
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{
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byte b = source[i];
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for (int shift = 0; shift < 8; shift += bits)
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{
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int colorIndex = (b >> (8 - bits - shift)) & mask;
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result[resultOffset] = (byte)colorIndex;
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resultOffset++;
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}
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}
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}
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else
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{
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result = source;
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}
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return result;
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}
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/// <summary>
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/// Reads the data chunk containing physical dimension data.
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="image">The image to read to.</param>
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/// <param name="data">The data containing physical data.</param>
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private void ReadPhysicalChunk<TColor>(Image<TColor> image, byte[] data)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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data.ReverseBytes(0, 4);
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data.ReverseBytes(4, 4);
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// 39.3700787 = inches in a meter.
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image.MetaData.HorizontalResolution = BitConverter.ToInt32(data, 0) / 39.3700787d;
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image.MetaData.VerticalResolution = BitConverter.ToInt32(data, 4) / 39.3700787d;
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}
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/// <summary>
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/// Calculates the correct number of bytes per pixel for the given color type.
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/// </summary>
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/// <returns>The <see cref="int"/></returns>
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private int CalculateBytesPerPixel()
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{
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switch (this.PngColorType)
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{
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case PngColorType.Grayscale:
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return 1;
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case PngColorType.GrayscaleWithAlpha:
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return 2;
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case PngColorType.Palette:
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return 1;
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case PngColorType.Rgb:
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return 3;
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// PngColorType.RgbWithAlpha:
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default:
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return 4;
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}
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}
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/// <summary>
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/// Calculates the scanline length.
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/// </summary>
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/// <param name="width">The width of the row.</param>
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/// <returns>
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/// The <see cref="int"/> representing the length.
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/// </returns>
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private int CalculateScanlineLength(int width)
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{
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int scanlineLength = width * this.header.BitDepth * this.bytesPerPixel;
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int amount = scanlineLength % 8;
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if (amount != 0)
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{
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scanlineLength += 8 - amount;
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}
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return scanlineLength / 8;
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}
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/// <summary>
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/// Reads the scanlines within the image.
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="dataStream">The <see cref="MemoryStream"/> containing data.</param>
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/// <param name="pixels"> The pixel data.</param>
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private void ReadScanlines<TColor>(MemoryStream dataStream, PixelAccessor<TColor> pixels)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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this.bytesPerPixel = this.CalculateBytesPerPixel();
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this.bytesPerScanline = this.CalculateScanlineLength(this.header.Width) + 1;
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this.bytesPerSample = 1;
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if (this.header.BitDepth >= 8)
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{
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this.bytesPerSample = this.header.BitDepth / 8;
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}
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dataStream.Position = 0;
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using (ZlibInflateStream compressedStream = new ZlibInflateStream(dataStream))
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{
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if (this.header.InterlaceMethod == PngInterlaceMode.Adam7)
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{
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this.DecodeInterlacedPixelData(compressedStream, pixels);
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}
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else
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{
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this.DecodePixelData(compressedStream, pixels);
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}
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}
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}
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/// <summary>
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/// Decodes the raw pixel data row by row
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="compressedStream">The compressed pixel data stream.</param>
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/// <param name="pixels">The image pixel accessor.</param>
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private void DecodePixelData<TColor>(Stream compressedStream, PixelAccessor<TColor> pixels)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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byte[] previousScanline = ArrayPool<byte>.Shared.Rent(this.bytesPerScanline);
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byte[] scanline = ArrayPool<byte>.Shared.Rent(this.bytesPerScanline);
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// Zero out the scanlines, because the bytes that are rented from the arraypool may not be zero.
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Array.Clear(scanline, 0, this.bytesPerScanline);
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Array.Clear(previousScanline, 0, this.bytesPerScanline);
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try
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{
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for (int y = 0; y < this.header.Height; y++)
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{
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compressedStream.Read(scanline, 0, this.bytesPerScanline);
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FilterType filterType = (FilterType)scanline[0];
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switch (filterType)
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{
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case FilterType.None:
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NoneFilter.Decode(scanline);
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break;
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case FilterType.Sub:
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SubFilter.Decode(scanline, this.bytesPerScanline, this.bytesPerPixel);
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break;
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case FilterType.Up:
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UpFilter.Decode(scanline, previousScanline, this.bytesPerScanline);
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break;
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case FilterType.Average:
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AverageFilter.Decode(scanline, previousScanline, this.bytesPerScanline, this.bytesPerPixel);
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break;
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case FilterType.Paeth:
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PaethFilter.Decode(scanline, previousScanline, this.bytesPerScanline, this.bytesPerPixel);
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break;
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default:
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throw new ImageFormatException("Unknown filter type.");
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}
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this.ProcessDefilteredScanline(scanline, y, pixels);
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Swap(ref scanline, ref previousScanline);
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}
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}
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finally
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{
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ArrayPool<byte>.Shared.Return(previousScanline);
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ArrayPool<byte>.Shared.Return(scanline);
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}
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}
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/// <summary>
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/// Decodes the raw interlaced pixel data row by row
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/// <see href="https://github.com/juehv/DentalImageViewer/blob/8a1a4424b15d6cc453b5de3f273daf3ff5e3a90d/DentalImageViewer/lib/jiu-0.14.3/net/sourceforge/jiu/codecs/PNGCodec.java"/>
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="compressedStream">The compressed pixel data stream.</param>
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/// <param name="pixels">The image pixel accessor.</param>
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private void DecodeInterlacedPixelData<TColor>(Stream compressedStream, PixelAccessor<TColor> pixels)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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byte[] previousScanline = ArrayPool<byte>.Shared.Rent(this.bytesPerScanline);
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byte[] scanline = ArrayPool<byte>.Shared.Rent(this.bytesPerScanline);
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try
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{
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for (int pass = 0; pass < 7; pass++)
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{
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// Zero out the scanlines, because the bytes that are rented from the arraypool may not be zero.
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Array.Clear(scanline, 0, this.bytesPerScanline);
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Array.Clear(previousScanline, 0, this.bytesPerScanline);
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int y = Adam7FirstRow[pass];
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int numColumns = this.ComputeColumnsAdam7(pass);
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if (numColumns == 0)
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{
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// This pass contains no data; skip to next pass
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continue;
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}
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int bytesPerInterlaceScanline = this.CalculateScanlineLength(numColumns) + 1;
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while (y < this.header.Height)
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{
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compressedStream.Read(scanline, 0, bytesPerInterlaceScanline);
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FilterType filterType = (FilterType)scanline[0];
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switch (filterType)
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{
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case FilterType.None:
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NoneFilter.Decode(scanline);
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break;
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case FilterType.Sub:
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SubFilter.Decode(scanline, bytesPerInterlaceScanline, this.bytesPerPixel);
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break;
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case FilterType.Up:
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UpFilter.Decode(scanline, previousScanline, bytesPerInterlaceScanline);
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break;
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case FilterType.Average:
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AverageFilter.Decode(scanline, previousScanline, bytesPerInterlaceScanline, this.bytesPerPixel);
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break;
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case FilterType.Paeth:
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PaethFilter.Decode(scanline, previousScanline, bytesPerInterlaceScanline, this.bytesPerPixel);
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break;
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default:
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throw new ImageFormatException("Unknown filter type.");
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}
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this.ProcessInterlacedDefilteredScanline(scanline, y, pixels, Adam7FirstColumn[pass], Adam7ColumnIncrement[pass]);
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Swap(ref scanline, ref previousScanline);
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y += Adam7RowIncrement[pass];
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}
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}
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}
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finally
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{
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ArrayPool<byte>.Shared.Return(previousScanline);
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ArrayPool<byte>.Shared.Return(scanline);
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}
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}
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/// <summary>
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/// Processes the de-filtered scanline filling the image pixel data
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/// </summary>
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/// <typeparam name="TColor">The pixel format.</typeparam>
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/// <param name="defilteredScanline">The de-filtered scanline</param>
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/// <param name="row">The current image row.</param>
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/// <param name="pixels">The image pixels</param>
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private void ProcessDefilteredScanline<TColor>(byte[] defilteredScanline, int row, PixelAccessor<TColor> pixels)
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where TColor : struct, IPackedPixel, IEquatable<TColor>
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{
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TColor color = default(TColor);
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switch (this.PngColorType)
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{
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case PngColorType.Grayscale:
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int factor = 255 / ((int)Math.Pow(2, this.header.BitDepth) - 1);
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byte[] newScanline1 = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
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for (int x = 0; x < this.header.Width; x++)
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{
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byte intensity = (byte)(newScanline1[x] * factor);
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color.PackFromBytes(intensity, intensity, intensity, 255);
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pixels[x, row] = color;
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}
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break;
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case PngColorType.GrayscaleWithAlpha:
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|
|
for (int x = 0; x < this.header.Width; x++)
|
|
{
|
|
int offset = 1 + (x * this.bytesPerPixel);
|
|
|
|
byte intensity = defilteredScanline[offset];
|
|
byte alpha = defilteredScanline[offset + this.bytesPerSample];
|
|
|
|
color.PackFromBytes(intensity, intensity, intensity, alpha);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.Palette:
|
|
|
|
byte[] newScanline = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
|
|
|
|
if (this.paletteAlpha != null && this.paletteAlpha.Length > 0)
|
|
{
|
|
// If the alpha palette is not null and has one or more entries, this means, that the image contains an alpha
|
|
// channel and we should try to read it.
|
|
for (int x = 0; x < this.header.Width; x++)
|
|
{
|
|
int index = newScanline[x];
|
|
int pixelOffset = index * 3;
|
|
|
|
byte a = this.paletteAlpha.Length > index ? this.paletteAlpha[index] : (byte)255;
|
|
|
|
if (a > 0)
|
|
{
|
|
byte r = this.palette[pixelOffset];
|
|
byte g = this.palette[pixelOffset + 1];
|
|
byte b = this.palette[pixelOffset + 2];
|
|
color.PackFromBytes(r, g, b, a);
|
|
}
|
|
else
|
|
{
|
|
color.PackFromBytes(0, 0, 0, 0);
|
|
}
|
|
|
|
pixels[x, row] = color;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
for (int x = 0; x < this.header.Width; x++)
|
|
{
|
|
int index = newScanline[x];
|
|
int pixelOffset = index * 3;
|
|
|
|
byte r = this.palette[pixelOffset];
|
|
byte g = this.palette[pixelOffset + 1];
|
|
byte b = this.palette[pixelOffset + 2];
|
|
|
|
color.PackFromBytes(r, g, b, 255);
|
|
pixels[x, row] = color;
|
|
}
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.Rgb:
|
|
|
|
for (int x = 0; x < this.header.Width; x++)
|
|
{
|
|
int offset = 1 + (x * this.bytesPerPixel);
|
|
|
|
byte r = defilteredScanline[offset];
|
|
byte g = defilteredScanline[offset + this.bytesPerSample];
|
|
byte b = defilteredScanline[offset + (2 * this.bytesPerSample)];
|
|
|
|
color.PackFromBytes(r, g, b, 255);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.RgbWithAlpha:
|
|
|
|
for (int x = 0; x < this.header.Width; x++)
|
|
{
|
|
int offset = 1 + (x * this.bytesPerPixel);
|
|
|
|
byte r = defilteredScanline[offset];
|
|
byte g = defilteredScanline[offset + this.bytesPerSample];
|
|
byte b = defilteredScanline[offset + (2 * this.bytesPerSample)];
|
|
byte a = defilteredScanline[offset + (3 * this.bytesPerSample)];
|
|
|
|
color.PackFromBytes(r, g, b, a);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Processes the interlaced de-filtered scanline filling the image pixel data
|
|
/// </summary>
|
|
/// <typeparam name="TColor">The pixel format.</typeparam>
|
|
/// <param name="defilteredScanline">The de-filtered scanline</param>
|
|
/// <param name="row">The current image row.</param>
|
|
/// <param name="pixels">The image pixels</param>
|
|
/// <param name="pixelOffset">The column start index. Always 0 for none interlaced images.</param>
|
|
/// <param name="increment">The column increment. Always 1 for none interlaced images.</param>
|
|
private void ProcessInterlacedDefilteredScanline<TColor>(byte[] defilteredScanline, int row, PixelAccessor<TColor> pixels, int pixelOffset = 0, int increment = 1)
|
|
where TColor : struct, IPackedPixel, IEquatable<TColor>
|
|
{
|
|
TColor color = default(TColor);
|
|
|
|
switch (this.PngColorType)
|
|
{
|
|
case PngColorType.Grayscale:
|
|
int factor = 255 / ((int)Math.Pow(2, this.header.BitDepth) - 1);
|
|
byte[] newScanline1 = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o++)
|
|
{
|
|
byte intensity = (byte)(newScanline1[o] * factor);
|
|
color.PackFromBytes(intensity, intensity, intensity, 255);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.GrayscaleWithAlpha:
|
|
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o += this.bytesPerPixel)
|
|
{
|
|
byte intensity = defilteredScanline[o];
|
|
byte alpha = defilteredScanline[o + this.bytesPerSample];
|
|
|
|
color.PackFromBytes(intensity, intensity, intensity, alpha);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.Palette:
|
|
|
|
byte[] newScanline = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
|
|
|
|
if (this.paletteAlpha != null && this.paletteAlpha.Length > 0)
|
|
{
|
|
// If the alpha palette is not null and has one or more entries, this means, that the image contains an alpha
|
|
// channel and we should try to read it.
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o++)
|
|
{
|
|
int index = newScanline[o];
|
|
int offset = index * 3;
|
|
|
|
byte a = this.paletteAlpha.Length > index ? this.paletteAlpha[index] : (byte)255;
|
|
|
|
if (a > 0)
|
|
{
|
|
byte r = this.palette[offset];
|
|
byte g = this.palette[offset + 1];
|
|
byte b = this.palette[offset + 2];
|
|
color.PackFromBytes(r, g, b, a);
|
|
}
|
|
else
|
|
{
|
|
color.PackFromBytes(0, 0, 0, 0);
|
|
}
|
|
|
|
pixels[x, row] = color;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o++)
|
|
{
|
|
int index = newScanline[o];
|
|
int offset = index * 3;
|
|
|
|
byte r = this.palette[offset];
|
|
byte g = this.palette[offset + 1];
|
|
byte b = this.palette[offset + 2];
|
|
|
|
color.PackFromBytes(r, g, b, 255);
|
|
pixels[x, row] = color;
|
|
}
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.Rgb:
|
|
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o += this.bytesPerPixel)
|
|
{
|
|
byte r = defilteredScanline[o];
|
|
byte g = defilteredScanline[o + this.bytesPerSample];
|
|
byte b = defilteredScanline[o + (2 * this.bytesPerSample)];
|
|
|
|
color.PackFromBytes(r, g, b, 255);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
|
|
case PngColorType.RgbWithAlpha:
|
|
|
|
for (int x = pixelOffset, o = 1; x < this.header.Width; x += increment, o += this.bytesPerPixel)
|
|
{
|
|
byte r = defilteredScanline[o];
|
|
byte g = defilteredScanline[o + this.bytesPerSample];
|
|
byte b = defilteredScanline[o + (2 * this.bytesPerSample)];
|
|
byte a = defilteredScanline[o + (3 * this.bytesPerSample)];
|
|
|
|
color.PackFromBytes(r, g, b, a);
|
|
pixels[x, row] = color;
|
|
}
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Reads a text chunk containing image properties from the data.
|
|
/// </summary>
|
|
/// <typeparam name="TColor">The pixel format.</typeparam>
|
|
/// <param name="image">The image to decode to.</param>
|
|
/// <param name="data">The <see cref="T:byte[]"/> containing data.</param>
|
|
/// <param name="length">The maximum length to read.</param>
|
|
private void ReadTextChunk<TColor>(Image<TColor> image, byte[] data, int length)
|
|
where TColor : struct, IPackedPixel, IEquatable<TColor>
|
|
{
|
|
int zeroIndex = 0;
|
|
|
|
for (int i = 0; i < length; i++)
|
|
{
|
|
if (data[i] == 0)
|
|
{
|
|
zeroIndex = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
string name = Encoding.Unicode.GetString(data, 0, zeroIndex);
|
|
string value = Encoding.Unicode.GetString(data, zeroIndex + 1, length - zeroIndex - 1);
|
|
|
|
image.MetaData.Properties.Add(new ImageProperty(name, value));
|
|
}
|
|
|
|
/// <summary>
|
|
/// Reads a header chunk from the data.
|
|
/// </summary>
|
|
/// <param name="data">The <see cref="T:byte[]"/> containing data.</param>
|
|
private void ReadHeaderChunk(byte[] data)
|
|
{
|
|
this.header = new PngHeader();
|
|
|
|
data.ReverseBytes(0, 4);
|
|
data.ReverseBytes(4, 4);
|
|
|
|
this.header.Width = BitConverter.ToInt32(data, 0);
|
|
this.header.Height = BitConverter.ToInt32(data, 4);
|
|
|
|
this.header.BitDepth = data[8];
|
|
this.header.ColorType = data[9];
|
|
this.header.CompressionMethod = data[10];
|
|
this.header.FilterMethod = data[11];
|
|
this.header.InterlaceMethod = (PngInterlaceMode)data[12];
|
|
}
|
|
|
|
/// <summary>
|
|
/// Validates the png header.
|
|
/// </summary>
|
|
/// <exception cref="NotSupportedException">
|
|
/// Thrown if the image does pass validation.
|
|
/// </exception>
|
|
private void ValidateHeader()
|
|
{
|
|
if (!ColorTypes.ContainsKey(this.header.ColorType))
|
|
{
|
|
throw new NotSupportedException("Color type is not supported or not valid.");
|
|
}
|
|
|
|
if (!ColorTypes[this.header.ColorType].Contains(this.header.BitDepth))
|
|
{
|
|
throw new NotSupportedException("Bit depth is not supported or not valid.");
|
|
}
|
|
|
|
if (this.header.FilterMethod != 0)
|
|
{
|
|
throw new NotSupportedException("The png specification only defines 0 as filter method.");
|
|
}
|
|
|
|
if (this.header.InterlaceMethod != PngInterlaceMode.None && this.header.InterlaceMethod != PngInterlaceMode.Adam7)
|
|
{
|
|
throw new NotSupportedException("The png specification only defines 'None' and 'Adam7' as interlaced methods.");
|
|
}
|
|
|
|
this.PngColorType = (PngColorType)this.header.ColorType;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Reads a chunk from the stream.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// The <see cref="PngChunk"/>.
|
|
/// </returns>
|
|
private PngChunk ReadChunk()
|
|
{
|
|
PngChunk chunk = new PngChunk();
|
|
this.ReadChunkLength(chunk);
|
|
if (chunk.Length < 0)
|
|
{
|
|
return null;
|
|
}
|
|
|
|
this.ReadChunkType(chunk);
|
|
this.ReadChunkData(chunk);
|
|
this.ReadChunkCrc(chunk);
|
|
|
|
return chunk;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Reads the cycle redundancy chunk from the data.
|
|
/// </summary>
|
|
/// <param name="chunk">The chunk.</param>
|
|
/// <exception cref="ImageFormatException">
|
|
/// Thrown if the input stream is not valid or corrupt.
|
|
/// </exception>
|
|
private void ReadChunkCrc(PngChunk chunk)
|
|
{
|
|
int numBytes = this.currentStream.Read(this.crcBuffer, 0, 4);
|
|
if (numBytes >= 1 && numBytes <= 3)
|
|
{
|
|
throw new ImageFormatException("Image stream is not valid!");
|
|
}
|
|
|
|
this.crcBuffer.ReverseBytes();
|
|
|
|
chunk.Crc = BitConverter.ToUInt32(this.crcBuffer, 0);
|
|
|
|
this.crc.Reset();
|
|
this.crc.Update(this.chunkTypeBuffer);
|
|
this.crc.Update(chunk.Data, 0, chunk.Length);
|
|
|
|
if (this.crc.Value != chunk.Crc)
|
|
{
|
|
throw new ImageFormatException("CRC Error. PNG Image chunk is corrupt!");
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Reads the chunk data from the stream.
|
|
/// </summary>
|
|
/// <param name="chunk">The chunk.</param>
|
|
private void ReadChunkData(PngChunk chunk)
|
|
{
|
|
// We rent the buffer here to return it afterwards in Decode()
|
|
chunk.Data = ArrayPool<byte>.Shared.Rent(chunk.Length);
|
|
this.currentStream.Read(chunk.Data, 0, chunk.Length);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Identifies the chunk type from the chunk.
|
|
/// </summary>
|
|
/// <param name="chunk">The chunk.</param>
|
|
/// <exception cref="ImageFormatException">
|
|
/// Thrown if the input stream is not valid.
|
|
/// </exception>
|
|
private void ReadChunkType(PngChunk chunk)
|
|
{
|
|
int numBytes = this.currentStream.Read(this.chunkTypeBuffer, 0, 4);
|
|
if (numBytes >= 1 && numBytes <= 3)
|
|
{
|
|
throw new ImageFormatException("Image stream is not valid!");
|
|
}
|
|
|
|
this.chars[0] = (char)this.chunkTypeBuffer[0];
|
|
this.chars[1] = (char)this.chunkTypeBuffer[1];
|
|
this.chars[2] = (char)this.chunkTypeBuffer[2];
|
|
this.chars[3] = (char)this.chunkTypeBuffer[3];
|
|
|
|
chunk.Type = new string(this.chars);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Calculates the length of the given chunk.
|
|
/// </summary>
|
|
/// <param name="chunk">The chunk.</param>
|
|
/// <exception cref="ImageFormatException">
|
|
/// Thrown if the input stream is not valid.
|
|
/// </exception>
|
|
private void ReadChunkLength(PngChunk chunk)
|
|
{
|
|
int numBytes = this.currentStream.Read(this.chunkLengthBuffer, 0, 4);
|
|
if (numBytes > 1 && numBytes <= 3)
|
|
{
|
|
throw new ImageFormatException("Image stream is not valid!");
|
|
}
|
|
|
|
if (numBytes <= 1)
|
|
{
|
|
chunk.Length = -1;
|
|
return;
|
|
}
|
|
|
|
this.chunkLengthBuffer.ReverseBytes();
|
|
|
|
chunk.Length = BitConverter.ToInt32(this.chunkLengthBuffer, 0);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns the correct number of columns for each interlaced pass.
|
|
/// </summary>
|
|
/// <param name="pass">Th current pass index</param>
|
|
/// <returns>The <see cref="int"/></returns>
|
|
private int ComputeColumnsAdam7(int pass)
|
|
{
|
|
int width = this.header.Width;
|
|
switch (pass)
|
|
{
|
|
case 0: return (width + 7) / 8;
|
|
case 1: return (width + 3) / 8;
|
|
case 2: return (width + 3) / 4;
|
|
case 3: return (width + 1) / 4;
|
|
case 4: return (width + 1) / 2;
|
|
case 5: return width / 2;
|
|
case 6: return width;
|
|
default: throw new ArgumentException($"Not a valid pass index: {pass}");
|
|
}
|
|
}
|
|
}
|
|
}
|
