public void TestZlibHeadersAreAddedBack()
{
IEnumerable <PNGChunk> chunks = PNGChunkParser.ChunksFromStream(new MemoryStream(Crushed10x10White));
IEnumerable <PNGChunk> decrushedChunks = PNGDecrusher.DecrushChunks(chunks);
PNGChunk decrushedIdatChunk = decrushedChunks.First(c => c.Type == PNGChunk.ChunkType.IDAT);
using (MemoryStream idatDataStream = new MemoryStream(decrushedIdatChunk.Data))
{
// basic check of the zlib header
// http://tools.ietf.org/html/rfc1950#page-4
int CMF = idatDataStream.ReadByte();
int FLG = idatDataStream.ReadByte();
int compressionMethod = CMF & 0x0F;
int compressionInfo = (CMF & 0xF0) >> 4;
int COMPRESSION_METHOD_DEFLATE = 8;
Assert.AreEqual(COMPRESSION_METHOD_DEFLATE, compressionMethod);
using (DeflateStream deflateStream = new DeflateStream(idatDataStream, CompressionMode.Decompress))
using (MemoryStream decompressedStream = new MemoryStream())
{
deflateStream.CopyTo(decompressedStream);
Assert.AreEqual(410, decompressedStream.Length);
}
}
}
public void TestChunksAreCorrectlyParsed()
{
using (MemoryStream stream = new MemoryStream(Simple10x10WhitePNG))
{
PNGChunk[] chunks = PNGChunkParser.ChunksFromStream(stream).ToArray();
Assert.AreEqual(6, chunks.Length);
PNGChunk idatChunk = chunks[4];
Assert.AreEqual("IDAT", idatChunk.TypeString);
Assert.AreEqual(PNGChunk.ChunkType.IDAT, idatChunk.Type);
Assert.AreEqual(17, idatChunk.Data.Length);
}
}
/// <summary>
/// Determines whether the <see cref="Stream"/> represents a crushed PNG image.
/// </summary>
/// <param name="input">
/// A <see cref="Stream"/> which contains a PNG image, which can be crushed or not.
/// </param>
/// <returns>
/// <see langword="true"/> if <paramref name="input"/> represents a crushed PNG image;
/// otherwise, <see langword="false"/>.
/// </returns>
public static bool CanDecrush(Stream input)
{
if (input == null)
{
throw new ArgumentNullException(nameof(input));
}
input.Seek(0, SeekOrigin.Begin);
var chunks = PNGChunkParser.ChunksFromStream(input);
return(chunks.Any(c => c.Type == PNGChunk.ChunkType.CgBI));
}
public void TestWritingChunksProducesIdenticalBytesAsInput()
{
byte[] input = Simple10x10WhitePNG;
using (MemoryStream stream = new MemoryStream(Simple10x10WhitePNG))
{
PNGChunk[] chunks = PNGChunkParser.ChunksFromStream(stream).ToArray();
MemoryStream output = new MemoryStream();
PNGChunkParser.WriteChunksAsPNG(chunks, output);
byte[] outputBytes = output.ToArray();
CollectionAssert.AreEqual(input, outputBytes);
}
}
public void TestWritingChunksAfterRecalculatingCRCProducesIdenticalBytesAsInput()
{
byte[] input = Simple10x10WhitePNG;
using (MemoryStream stream = new MemoryStream(Simple10x10WhitePNG))
{
PNGChunk[] chunks = PNGChunkParser.ChunksFromStream(stream).ToArray();
chunks = chunks.Select(c =>
{
return(new PNGChunk(c.TypeString, c.Data, PNGDecrusher.CalculateCRCForChunk(c.TypeString, c.Data)));
}).ToArray();
MemoryStream output = new MemoryStream();
PNGChunkParser.WriteChunksAsPNG(chunks, output);
byte[] outputBytes = output.ToArray();
CollectionAssert.AreEqual(input, outputBytes);
}
}
public void TestCRCCalculation()
{
byte[][] validPNGs =
{
Simple10x10WhitePNG,
Crushed10x10White,
CrushedFiftyPercentAlphaKindaBlue10x10
};
foreach (byte[] png in validPNGs)
{
IEnumerable <PNGChunk> chunks = PNGChunkParser.ChunksFromStream(new MemoryStream(Simple10x10WhitePNG));
foreach (PNGChunk chunk in chunks)
{
uint expectedCRC = chunk.DataCRC;
uint recalculatedCRC = PNGDecrusher.CalculateCRCForChunk(chunk.TypeString, chunk.Data);
Assert.AreEqual(expectedCRC, recalculatedCRC);
}
}
}
private static void DecrushAtChunkLevel(Stream input, Stream output)
{
IEnumerable <PNGChunk> fixedChunks = DecrushChunks(PNGChunkParser.ChunksFromStream(input));
PNGChunkParser.WriteChunksAsPNG(fixedChunks, output);
}