/// <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.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 DeflateStream(new MemoryStream(compressedProfile), CompressionMode.Decompress))
// 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(_latin1Encoding);
var bytesLeft = bytes.Length - keyword.Length - 1;
var value = reader.GetNullTerminatedStringValue(bytesLeft, _latin1Encoding);
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.zTXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(_latin1Encoding);
var compressionMethod = reader.GetSByte();
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - 1;
byte[] textBytes = null;
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.zTXt);
directory.AddError("Invalid compression method 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, _latin1Encoding))
};
var directory = new PngDirectory(PngChunkType.zTXt);
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(_latin1Encoding);
var compressionFlag = reader.GetSByte();
var compressionMethod = reader.GetSByte();
// TODO we currently ignore languageTagBytes and translatedKeywordBytes
var languageTagBytes = reader.GetNullTerminatedBytes(bytes.Length);
var translatedKeywordBytes = reader.GetNullTerminatedBytes(bytes.Length);
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - languageTagBytes.Length - 1 - translatedKeywordBytes.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, _latin1Encoding))
};
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);
}
}
/// <exception cref="PngProcessingException"/>
/// <exception cref="System.IO.IOException"/>
private static IEnumerable <Directory> ProcessChunk(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.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;
// http://george.chiramattel.com/blog/2007/09/deflatestream-block-length-does-not-match.html
// First two bytes are part of the zlib specification (RFC 1950), not the deflate specification (RFC 1951).
reader.Skip(2);
bytesLeft -= 2;
var compressedProfile = reader.GetBytes(bytesLeft);
IccDirectory?iccDirectory = null;
Exception? ex = null;
try
{
using var inflaterStream = new DeflateStream(new MemoryStream(compressedProfile), CompressionMode.Decompress);
iccDirectory = new IccReader().Extract(new IndexedCapturingReader(inflaterStream));
iccDirectory.Parent = directory;
}
catch (Exception e)
{
ex = e;
}
if (iccDirectory != null)
{
yield return(iccDirectory);
}
else if (ex != null)
{
directory.AddError($"Exception decompressing {nameof(PngChunkType.iCCP)} chunk: {ex.Message}");
}
}
else
{
directory.AddError("Invalid compression method value");
}
yield return(directory);
}
else if (chunkType == PngChunkType.bKGD)
{
var directory = new PngDirectory(PngChunkType.bKGD);
directory.Set(PngDirectory.TagBackgroundColor, bytes);
yield return(directory);
}
else if (chunkType == PngChunkType.tEXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(_latin1Encoding);
var bytesLeft = bytes.Length - keyword.Length - 1;
var value = reader.GetNullTerminatedStringValue(bytesLeft, _latin1Encoding);
var textPairs = new List <KeyValuePair> {
new KeyValuePair(keyword, value)
};
var directory = new PngDirectory(PngChunkType.tEXt);
directory.Set(PngDirectory.TagTextualData, textPairs);
yield return(directory);
}
else if (chunkType == PngChunkType.zTXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(_latin1Encoding);
var compressionMethod = reader.GetSByte();
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - 1;
byte[]? textBytes = null;
if (compressionMethod == 0)
{
if (!TryDeflate(bytes, bytesLeft, out textBytes, out string?errorMessage))
{
var directory = new PngDirectory(PngChunkType.zTXt);
directory.AddError($"Exception decompressing {nameof(PngChunkType.zTXt)} chunk with keyword \"{keyword}\": {errorMessage}");
yield return(directory);
}
}
else
{
var directory = new PngDirectory(PngChunkType.zTXt);
directory.AddError("Invalid compression method value");
yield return(directory);
}
if (textBytes != null)
{
foreach (var directory in ProcessTextChunk(keyword, textBytes))
{
yield return(directory);
}
}
}
else if (chunkType == PngChunkType.iTXt)
{
var reader = new SequentialByteArrayReader(bytes);
var keyword = reader.GetNullTerminatedStringValue(maxLengthBytes: 79).ToString(_latin1Encoding);
var compressionFlag = reader.GetSByte();
var compressionMethod = reader.GetSByte();
// TODO we currently ignore languageTagBytes and translatedKeywordBytes
var languageTagBytes = reader.GetNullTerminatedBytes(bytes.Length);
var translatedKeywordBytes = reader.GetNullTerminatedBytes(bytes.Length);
var bytesLeft = bytes.Length - keyword.Length - 1 - 1 - 1 - languageTagBytes.Length - 1 - translatedKeywordBytes.Length - 1;
byte[]? textBytes = null;
if (compressionFlag == 0)
{
textBytes = reader.GetNullTerminatedBytes(bytesLeft);
}
else if (compressionFlag == 1)
{
if (compressionMethod == 0)
{
if (!TryDeflate(bytes, bytesLeft, out textBytes, out string?errorMessage))
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError($"Exception decompressing {nameof(PngChunkType.iTXt)} chunk with keyword \"{keyword}\": {errorMessage}");
yield return(directory);
}
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression method value");
yield return(directory);
}
}
else
{
var directory = new PngDirectory(PngChunkType.iTXt);
directory.AddError("Invalid compression flag value");
yield return(directory);
}
if (textBytes != null)
{
foreach (var directory in ProcessTextChunk(keyword, textBytes))
{
yield return(directory);
}
}
}
else if (chunkType == PngChunkType.tIME)
{
var reader = new SequentialByteArrayReader(bytes);
var year = reader.GetUInt16();
var month = reader.GetByte();
int day = reader.GetByte();
int hour = reader.GetByte();
int minute = reader.GetByte();
int second = reader.GetByte();
var directory = new PngDirectory(PngChunkType.tIME);
if (DateUtil.IsValidDate(year, month, day) && DateUtil.IsValidTime(hour, minute, second))
{
var time = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Unspecified);
directory.Set(PngDirectory.TagLastModificationTime, time);
}
else
{
directory.AddError($"PNG tIME data describes an invalid date/time: year={year} month={month} day={day} hour={hour} minute={minute} second={second}");
}
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);
}
yield break;
IEnumerable <Directory> ProcessTextChunk(string keyword, byte[] textBytes)
{
if (keyword == "XML:com.adobe.xmp")
{
yield return(new XmpReader().Extract(textBytes));
}
else if (keyword == "Raw profile type xmp")
{
if (TryProcessRawProfile(out int byteCount))
{
yield return(new XmpReader().Extract(textBytes, 0, byteCount));
}
else
{
yield return(ReadTextDirectory(keyword, textBytes, chunkType));
}
}
else if (keyword == "Raw profile type exif" || keyword == "Raw profile type APP1")
{
if (TryProcessRawProfile(out _))
{
foreach (var exifDirectory in new ExifReader().Extract(new ByteArrayReader(textBytes)))
{
yield return(exifDirectory);
}
}
else
{
yield return(ReadTextDirectory(keyword, textBytes, chunkType));
}
}
else if (keyword == "Raw profile type icc" || keyword == "Raw profile type icm")
{
if (TryProcessRawProfile(out _))
{
yield return(new IccReader().Extract(new ByteArrayReader(textBytes)));
}
else
{
yield return(ReadTextDirectory(keyword, textBytes, chunkType));
}
}
else if (keyword == "Raw profile type iptc")
{
if (TryProcessRawProfile(out int byteCount))
{
yield return(new IptcReader().Extract(new SequentialByteArrayReader(textBytes), byteCount));
}
else
{
yield return(ReadTextDirectory(keyword, textBytes, chunkType));
}
}
else
{
yield return(ReadTextDirectory(keyword, textBytes, chunkType));
}
PngDirectory ReadTextDirectory(string keyword, byte[] textBytes, PngChunkType pngChunkType)
{
var textPairs = new[] { new KeyValuePair(keyword, new StringValue(textBytes, _latin1Encoding)) };
var directory = new PngDirectory(pngChunkType);
directory.Set(PngDirectory.TagTextualData, textPairs);
return(directory);
}
bool TryProcessRawProfile(out int byteCount)
{
// Raw profiles have form "\n<name>\n<length>\n<hex>\n"
if (textBytes.Length == 0 || textBytes[0] != '\n')
{
byteCount = default;
return(false);
}
var i = 1;
// Skip name
while (i < textBytes.Length && textBytes[i] != '\n')
{
i++;
}
if (i == textBytes.Length)
{
byteCount = default;
return(false);
}
// Read length
int length = 0;
while (true)
{
i++;
var c = (char)textBytes[i];
if (c == ' ')
{
continue;
}
if (c == '\n')
{
break;
}
if (c >= '0' && c <= '9')
{
length *= 10;
length += c - '0';
}
else
{
byteCount = default;
return(false);
}
}
i++;
// We should be at the ASCII-encoded hex data. Walk through the remaining bytes, re-writing as raw bytes
// starting at offset zero in the array. We have to skip \n characters.
// Validate the data can be correctly parsed before modifying it in-place, because if parsing fails later
// consumers may want the unmodified data.
// Each row must have 72 characters (36 bytes once decoded) separated by \n
const int rowCharCount = 72;
int charsInRow = rowCharCount;
for (int j = i; j < length + i; j++)
{
byte c = textBytes[j];
if (charsInRow-- == 0)
{
if (c != '\n')
{
byteCount = default;
return(false);
}
charsInRow = rowCharCount;
continue;
}
if ((c < '0' || c > '9') && (c < 'a' || c > 'f') && (c < 'A' || c > 'F'))
{
byteCount = default;
return(false);
}
}
byteCount = length;
var writeIndex = 0;
charsInRow = rowCharCount;
while (length > 0)
{
var c1 = textBytes[i++];
if (charsInRow-- == 0)
{
Debug.Assert(c1 == '\n');
charsInRow = rowCharCount;
continue;
}
var c2 = textBytes[i++];
charsInRow--;
var n1 = ParseHexNibble(c1);
var n2 = ParseHexNibble(c2);
length--;
textBytes[writeIndex++] = (byte)((n1 << 4) | n2);
}
return(writeIndex == byteCount);
static int ParseHexNibble(int h)
{
if (h >= '0' && h <= '9')
{
return(h - '0');
}
if (h >= 'a' && h <= 'f')
{
return(10 + (h - 'a'));
}
if (h >= 'A' && h <= 'F')
{
return(10 + (h - 'A'));
}
Debug.Fail("Should not reach here");
throw new InvalidOperationException();
}
}