/// <summary>
/// Decodes per-row delta-encoded and then Deflate-compressed data from a source stream and writes the decoded
/// data to a target stream.
/// </summary>
/// <remarks><paramref name="source"/> must already be at the correct position.</remarks>
/// <param name="source">The stream from which to copy the data.</param>
/// <param name="dest">The stream to which to copy the data.</param>
/// <param name="length">
/// The number of bytes to copy from the source stream, or <c>null</c> to copy all data until the source stream
/// ends.
/// </param>
/// <param name="depth">The depth of the image in bits per pixel color component.</param>
/// <param name="imageWidth">The width of the image in pixels.</param>
/// <param name="cancelToken">
/// A cancellation token which allows copying to be cancelled before it completes.
/// </param>
public static void DecodeZipPredicted(Stream source, Stream dest, long?length, int depth, int imageWidth,
CancellationToken cancelToken = default(CancellationToken))
{
if (depth == 1 || depth == 8)
{
// no prediction here
DecodeZip(source, dest, length, cancelToken);
return;
}
Stream actualSource = length.HasValue
? new PartialStream(source, source.Position, length.Value)
: source;
// skip zlib header
source.ReadBytes(2);
var buf = new byte[imageWidth * (depth / 8)];
using (var inflater = new DeflateStream(actualSource, CompressionMode.Decompress, leaveOpen: true))
{
for (;;)
{
try
{
inflater.ReadBytes(buf);
}
catch (EndOfStreamException)
{
break;
}
if (depth == 16)
{
DeltaEncoding.DeltaDecodeBigEndian16(buf);
dest.Write(buf, 0, buf.Length);
}
else if (depth == 32)
{
DeltaEncoding.DeltaDecodeBigEndian32(buf);
dest.Write(buf, 0, buf.Length);
}
cancelToken.ThrowIfCancellationRequested();
}
}
}
public byte[] GetTrueBytes(FileEntry entry)
{
if (!entry.IsCompressed)
{
return(GetRawBytes(entry));
}
if (entry.OriginalData != null)
{
using (var ms = new MemoryStream(entry.OriginalData))
using (var ds = new DeflateStream(ms, CompressionMode.Decompress))
{
return(ds.ReadBytes(entry.Length));
}
}
using (Stream s = GetStream(entry))
using (DeflateStream ds = new DeflateStream(s, CompressionMode.Decompress))
{
return(ds.ReadBytes(entry.Length));
}
}
public Png(Stream s)
{
if (!Verify(s))
{
throw new InvalidDataException("PNG Signature is bogus");
}
s.Position += 8;
var headerParsed = false;
var data = new List <byte>();
for (;;)
{
var length = IPAddress.NetworkToHostOrder(s.ReadInt32());
var type = Encoding.UTF8.GetString(s.ReadBytes(4));
var content = s.ReadBytes(length);
/*var crc = */ s.ReadInt32();
if (!headerParsed && type != "IHDR")
{
throw new InvalidDataException("Invalid PNG file - header does not appear first.");
}
using (var ms = new MemoryStream(content))
{
switch (type)
{
case "IHDR":
{
if (headerParsed)
{
throw new InvalidDataException("Invalid PNG file - duplicate header.");
}
Width = IPAddress.NetworkToHostOrder(ms.ReadInt32());
Height = IPAddress.NetworkToHostOrder(ms.ReadInt32());
Data = new byte[Width * Height];
var bitDepth = ms.ReadUInt8();
var colorType = (PngColorType)ms.ReadByte();
PixelFormat = MakePixelFormat(bitDepth, colorType);
var compression = ms.ReadByte();
/*var filter = */ ms.ReadByte();
var interlace = ms.ReadByte();
if (compression != 0)
{
throw new InvalidDataException("Compression method not supported");
}
if (interlace != 0)
{
throw new InvalidDataException("Interlacing not supported");
}
headerParsed = true;
break;
}
case "PLTE":
{
Palette = new Color[256];
for (var i = 0; i < length / 3; i++)
{
var r = ms.ReadByte(); var g = ms.ReadByte(); var b = ms.ReadByte();
Palette[i] = Color.FromArgb(r, g, b);
}
break;
}
case "tRNS":
{
if (Palette == null)
{
throw new InvalidDataException("Non-Palette indexed PNG are not supported.");
}
for (var i = 0; i < length; i++)
{
Palette[i] = Color.FromArgb(ms.ReadByte(), Palette[i]);
}
break;
}
case "IDAT":
{
data.AddRange(content);
break;
}
case "tEXt":
{
var key = ms.ReadASCIIZ();
EmbeddedData.Add(key, ms.ReadASCII(length - key.Length - 1));
break;
}
case "IEND":
{
using (var ns = new MemoryStream(data.ToArray()))
{
// 'zlib' flags bytes; confuses the DeflateStream.
/*var flags = (byte)*/ ns.ReadByte();
/*var moreFlags = (byte)*/ ns.ReadByte();
using (var ds = new DeflateStream(ns, CompressionMode.Decompress))
{
var prevLine = new byte[Width]; // all zero
for (var y = 0; y < Height; y++)
{
var filter = (PngFilter)ds.ReadByte();
var line = ds.ReadBytes(Width);
for (var i = 0; i < Width; i++)
{
line[i] = i > 0
? UnapplyFilter(filter, line[i], line[i - 1], prevLine[i], prevLine[i - 1])
: UnapplyFilter(filter, line[i], 0, prevLine[i], 0);
}
Array.Copy(line, 0, Data, y * Width, line.Length);
prevLine = line;
}
}
}
if (Palette == null)
{
throw new InvalidDataException("Non-Palette indexed PNG are not supported.");
}
return;
}
}
}
}
}
