/// <exception cref="PngProcessingException"/>
/// <exception cref="System.IO.IOException"/>
private static IEnumerable<Directory> ProcessChunk([NotNull] PngChunk chunk)
{
var chunkType = chunk.ChunkType;
var bytes = chunk.Bytes;
if (chunkType == PngChunkType.IHDR)
{
var header = new PngHeader(bytes);
var directory = new PngDirectory(PngChunkType.IHDR);
directory.Set(PngDirectory.TagImageWidth, header.ImageWidth);
directory.Set(PngDirectory.TagImageHeight, header.ImageHeight);
directory.Set(PngDirectory.TagBitsPerSample, header.BitsPerSample);
directory.Set(PngDirectory.TagColorType, header.ColorType.NumericValue);
directory.Set(PngDirectory.TagCompressionType, header.CompressionType);
directory.Set(PngDirectory.TagFilterMethod, header.FilterMethod);
directory.Set(PngDirectory.TagInterlaceMethod, header.InterlaceMethod);
yield return directory;
}
else if (chunkType == PngChunkType.PLTE)
{
var directory = new PngDirectory(PngChunkType.PLTE);
directory.Set(PngDirectory.TagPaletteSize, bytes.Length / 3);
yield return directory;
}
else if (chunkType == PngChunkType.tRNS)
{
var directory = new PngDirectory(PngChunkType.tRNS);
directory.Set(PngDirectory.TagPaletteHasTransparency, 1);
yield return directory;
}
else if (chunkType == PngChunkType.sRGB)
{
int srgbRenderingIntent = unchecked((sbyte)bytes[0]);
var directory = new PngDirectory(PngChunkType.sRGB);
directory.Set(PngDirectory.TagSrgbRenderingIntent, srgbRenderingIntent);
yield return directory;
}
else if (chunkType == PngChunkType.cHRM)
{
var chromaticities = new PngChromaticities(bytes);
var directory = new PngChromaticitiesDirectory();
directory.Set(PngChromaticitiesDirectory.TagWhitePointX, chromaticities.WhitePointX);
directory.Set(PngChromaticitiesDirectory.TagWhitePointY, chromaticities.WhitePointY);
directory.Set(PngChromaticitiesDirectory.TagRedX, chromaticities.RedX);
directory.Set(PngChromaticitiesDirectory.TagRedY, chromaticities.RedY);
directory.Set(PngChromaticitiesDirectory.TagGreenX, chromaticities.GreenX);
directory.Set(PngChromaticitiesDirectory.TagGreenY, chromaticities.GreenY);
directory.Set(PngChromaticitiesDirectory.TagBlueX, chromaticities.BlueX);
directory.Set(PngChromaticitiesDirectory.TagBlueY, chromaticities.BlueY);
yield return directory;
}
else if (chunkType == PngChunkType.gAMA)
{
var gammaInt = ByteConvert.ToInt32BigEndian(bytes);
var directory = new PngDirectory(PngChunkType.gAMA);
directory.Set(PngDirectory.TagGamma, gammaInt / 100000.0);
yield return directory;
}
else if (chunkType == PngChunkType.iCCP)
{
var reader = new SequentialByteArrayReader(bytes);
var profileName = reader.GetNullTerminatedString(maxLengthBytes: 79);
var directory = new PngDirectory(PngChunkType.iCCP);
directory.Set(PngDirectory.TagIccProfileName, profileName);
var compressionMethod = reader.GetSByte();
if (compressionMethod == 0)
{
// Only compression method allowed by the spec is zero: deflate
// This assumes 1-byte-per-char, which it is by spec.
var bytesLeft = bytes.Length - profileName.Length - 2;
var compressedProfile = reader.GetBytes(bytesLeft);
using (var inflaterStream = new InflaterInputStream(new MemoryStream(compressedProfile)))
yield return new IccReader().Extract(new IndexedCapturingReader(inflaterStream));
}
else
{
directory.AddError("Invalid compression method value");
}
yield return directory;
}
else if (chunkType == PngChunkType.bKGD)
{
var directory = new PngDirectory(PngChunkType.bKGD);
directory.Set(PngDirectory.TagBackgroundColor, bytes);
yield return directory;
}
else if (chunkType == PngChunkType.tEXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedString(maxLengthBytes: 79);
var bytesLeft = bytes.Length - keyword.Length - 1;
var value = reader.GetNullTerminatedString(bytesLeft);
var textPairs = new List<KeyValuePair> { new KeyValuePair(keyword, value) };
var directory = new PngDirectory(PngChunkType.iTXt);
directory.Set(PngDirectory.TagTextualData, textPairs);
yield return directory;
}
else if (chunkType == PngChunkType.iTXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedString(maxLengthBytes: 79);
var compressionFlag = reader.GetSByte();
var compressionMethod = reader.GetSByte();
var languageTag = reader.GetNullTerminatedString(bytes.Length);
var translatedKeyword = reader.GetNullTerminatedString(bytes.Length);
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - languageTag.Length - 1 - translatedKeyword.Length - 1;
string text = null;
if (compressionFlag == 0)
{
text = reader.GetNullTerminatedString(bytesLeft);
}
else if (compressionFlag == 1)
{
if (compressionMethod == 0)
{
using (var inflaterStream = new DeflateStream(new MemoryStream(bytes, bytes.Length - bytesLeft, bytesLeft), CompressionMode.Decompress))
text = new StreamReader(inflaterStream).ReadToEnd();
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression method value");
yield return directory;
}
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression flag value");
yield return directory;
}
if (text != null)
{
if (keyword == "XML:com.adobe.xmp")
{
// NOTE in testing images, the XMP has parsed successfully, but we are not extracting tags from it as necessary
yield return new XmpReader().Extract(text);
}
else
{
var textPairs = new List<KeyValuePair> { new KeyValuePair(keyword, text) };
var directory = new PngDirectory(PngChunkType.iTXt);
directory.Set(PngDirectory.TagTextualData, textPairs);
yield return directory;
}
}
}
else if (chunkType == PngChunkType.tIME)
{
var reader = new SequentialByteArrayReader(bytes);
var year = reader.GetUInt16();
var month = reader.GetByte();
int day = reader.GetByte();
int hour = reader.GetByte();
int minute = reader.GetByte();
int second = reader.GetByte();
var directory = new PngDirectory(PngChunkType.tIME);
try
{
var time = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Utc);
directory.Set(PngDirectory.TagLastModificationTime, time);
}
catch (ArgumentOutOfRangeException e)
{
directory.AddError("Error constructing DateTime: " + e.Message);
}
yield return directory;
}
else if (chunkType == PngChunkType.pHYs)
{
var reader = new SequentialByteArrayReader(bytes);
var pixelsPerUnitX = reader.GetInt32();
var pixelsPerUnitY = reader.GetInt32();
var unitSpecifier = reader.GetSByte();
var directory = new PngDirectory(PngChunkType.pHYs);
directory.Set(PngDirectory.TagPixelsPerUnitX, pixelsPerUnitX);
directory.Set(PngDirectory.TagPixelsPerUnitY, pixelsPerUnitY);
directory.Set(PngDirectory.TagUnitSpecifier, unitSpecifier);
yield return directory;
}
else if (chunkType.Equals(PngChunkType.sBIT))
{
var directory = new PngDirectory(PngChunkType.sBIT);
directory.Set(PngDirectory.TagSignificantBits, bytes);
yield return directory;
}
}
/// <exception cref="PngProcessingException"/>
/// <exception cref="System.IO.IOException"/>
private static IEnumerable<Directory> ProcessChunk([NotNull] PngChunk chunk)
{
// For more guidance:
// http://www.w3.org/TR/PNG-Decoders.html#D.Text-chunk-processing
// http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.iCCP
// by spec, PNG is generally supposed to use this encoding
const string defaultEncodingName = "ISO-8859-1";
var defaultEncoding = Encoding.GetEncoding(defaultEncodingName);
var chunkType = chunk.ChunkType;
var bytes = chunk.Bytes;
if (chunkType == PngChunkType.IHDR)
{
var header = new PngHeader(bytes);
var directory = new PngDirectory(PngChunkType.IHDR);
directory.Set(PngDirectory.TagImageWidth, header.ImageWidth);
directory.Set(PngDirectory.TagImageHeight, header.ImageHeight);
directory.Set(PngDirectory.TagBitsPerSample, header.BitsPerSample);
directory.Set(PngDirectory.TagColorType, header.ColorType.NumericValue);
directory.Set(PngDirectory.TagCompressionType, header.CompressionType);
directory.Set(PngDirectory.TagFilterMethod, header.FilterMethod);
directory.Set(PngDirectory.TagInterlaceMethod, header.InterlaceMethod);
yield return directory;
}
else if (chunkType == PngChunkType.PLTE)
{
var directory = new PngDirectory(PngChunkType.PLTE);
directory.Set(PngDirectory.TagPaletteSize, bytes.Length / 3);
yield return directory;
}
else if (chunkType == PngChunkType.tRNS)
{
var directory = new PngDirectory(PngChunkType.tRNS);
directory.Set(PngDirectory.TagPaletteHasTransparency, 1);
yield return directory;
}
else if (chunkType == PngChunkType.sRGB)
{
int srgbRenderingIntent = unchecked((sbyte)bytes[0]);
var directory = new PngDirectory(PngChunkType.sRGB);
directory.Set(PngDirectory.TagSrgbRenderingIntent, srgbRenderingIntent);
yield return directory;
}
else if (chunkType == PngChunkType.cHRM)
{
var chromaticities = new PngChromaticities(bytes);
var directory = new PngChromaticitiesDirectory();
directory.Set(PngChromaticitiesDirectory.TagWhitePointX, chromaticities.WhitePointX);
directory.Set(PngChromaticitiesDirectory.TagWhitePointY, chromaticities.WhitePointY);
directory.Set(PngChromaticitiesDirectory.TagRedX, chromaticities.RedX);
directory.Set(PngChromaticitiesDirectory.TagRedY, chromaticities.RedY);
directory.Set(PngChromaticitiesDirectory.TagGreenX, chromaticities.GreenX);
directory.Set(PngChromaticitiesDirectory.TagGreenY, chromaticities.GreenY);
directory.Set(PngChromaticitiesDirectory.TagBlueX, chromaticities.BlueX);
directory.Set(PngChromaticitiesDirectory.TagBlueY, chromaticities.BlueY);
yield return directory;
}
else if (chunkType == PngChunkType.gAMA)
{
var gammaInt = ByteConvert.ToInt32BigEndian(bytes);
var directory = new PngDirectory(PngChunkType.gAMA);
directory.Set(PngDirectory.TagGamma, gammaInt / 100000.0);
yield return directory;
}
else if (chunkType == PngChunkType.iCCP)
{
var reader = new SequentialByteArrayReader(bytes);
var profileName = reader.GetNullTerminatedStringValue(maxLengthBytes: 79);
var directory = new PngDirectory(PngChunkType.iCCP);
directory.Set(PngDirectory.TagIccProfileName, profileName);
var compressionMethod = reader.GetSByte();
if (compressionMethod == 0)
{
// Only compression method allowed by the spec is zero: deflate
// This assumes 1-byte-per-char, which it is by spec.
var bytesLeft = bytes.Length - profileName.Bytes.Length - 2;
var compressedProfile = reader.GetBytes(bytesLeft);
using (var inflaterStream = new InflaterInputStream(new MemoryStream(compressedProfile)))
{
var iccDirectory = new IccReader().Extract(new IndexedCapturingReader(inflaterStream));
iccDirectory.Parent = directory;
yield return iccDirectory;
}
}
else
{
directory.AddError("Invalid compression method value");
}
yield return directory;
}
else if (chunkType == PngChunkType.bKGD)
{
var directory = new PngDirectory(PngChunkType.bKGD);
directory.Set(PngDirectory.TagBackgroundColor, bytes);
yield return directory;
}
else if (chunkType == PngChunkType.tEXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(defaultEncoding);
var bytesLeft = bytes.Length - keyword.Length - 1;
var value = reader.GetNullTerminatedStringValue(bytesLeft, defaultEncoding);
var textPairs = new List<KeyValuePair> { new KeyValuePair(keyword, value) };
var directory = new PngDirectory(PngChunkType.iTXt);
directory.Set(PngDirectory.TagTextualData, textPairs);
yield return directory;
}
else if (chunkType == PngChunkType.iTXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(defaultEncoding);
var compressionFlag = reader.GetSByte();
var compressionMethod = reader.GetSByte();
var languageTag = reader.GetNullTerminatedStringValue(bytes.Length, defaultEncoding);
var translatedKeyword = reader.GetNullTerminatedStringValue(bytes.Length, defaultEncoding);
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - languageTag.Bytes.Length - 1 - translatedKeyword.Bytes.Length - 1;
byte[] textBytes = null;
if (compressionFlag == 0)
{
textBytes = reader.GetNullTerminatedBytes(bytesLeft);
}
else if (compressionFlag == 1)
{
if (compressionMethod == 0)
{
using (var inflaterStream = new DeflateStream(new MemoryStream(bytes, bytes.Length - bytesLeft, bytesLeft), CompressionMode.Decompress))
using (var decompStream = new MemoryStream())
{
#if !NET35
inflaterStream.CopyTo(decompStream);
#else
byte[] buffer = new byte[256];
int count;
int totalBytes = 0;
while ((count = inflaterStream.Read(buffer, 0, 256)) > 0)
{
decompStream.Write(buffer, 0, count);
totalBytes += count;
}
#endif
textBytes = decompStream.ToArray();
}
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression method value");
yield return directory;
}
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression flag value");
yield return directory;
}
if (textBytes != null)
{
if (keyword == "XML:com.adobe.xmp")
{
// NOTE in testing images, the XMP has parsed successfully, but we are not extracting tags from it as necessary
yield return new XmpReader().Extract(textBytes);
}
else
{
var textPairs = new List<KeyValuePair> { new KeyValuePair(keyword, new StringValue(textBytes, defaultEncoding)) };
var directory = new PngDirectory(PngChunkType.iTXt);
directory.Set(PngDirectory.TagTextualData, textPairs);
yield return directory;
}
}
}
else if (chunkType == PngChunkType.tIME)
{
var reader = new SequentialByteArrayReader(bytes);
var year = reader.GetUInt16();
var month = reader.GetByte();
int day = reader.GetByte();
int hour = reader.GetByte();
int minute = reader.GetByte();
int second = reader.GetByte();
var directory = new PngDirectory(PngChunkType.tIME);
try
{
var time = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Unspecified);
directory.Set(PngDirectory.TagLastModificationTime, time);
}
catch (ArgumentOutOfRangeException e)
{
directory.AddError("Error constructing DateTime: " + e.Message);
}
yield return directory;
}
else if (chunkType == PngChunkType.pHYs)
{
var reader = new SequentialByteArrayReader(bytes);
var pixelsPerUnitX = reader.GetInt32();
var pixelsPerUnitY = reader.GetInt32();
var unitSpecifier = reader.GetSByte();
var directory = new PngDirectory(PngChunkType.pHYs);
directory.Set(PngDirectory.TagPixelsPerUnitX, pixelsPerUnitX);
directory.Set(PngDirectory.TagPixelsPerUnitY, pixelsPerUnitY);
directory.Set(PngDirectory.TagUnitSpecifier, unitSpecifier);
yield return directory;
}
else if (chunkType.Equals(PngChunkType.sBIT))
{
var directory = new PngDirectory(PngChunkType.sBIT);
directory.Set(PngDirectory.TagSignificantBits, bytes);
yield return directory;
}
}