/// <summary>
/// Reads an item of additional layer information within the additional layer information subsection of a
/// PSD layer and mask information section from a stream and either returns a
/// <see cref="PSDAdditionalLayerInformation"/> object containing the additional information, or (if this
/// is an "out-of-band" layer information block) populates a <see cref="PSDFile"/> with the layer
/// information within.
/// </summary>
/// <param name="psd">
/// The PSD file object to populate if this is an "out-of-band" layer information block.
/// </param>
/// <param name="stream">The stream from which to read the layer information subsection.</param>
/// <returns>
/// The additional layer information, or <c>null</c> if the encountered block is an "out-of-band" layer
/// information block.
/// </returns>
public static PSDAdditionalLayerInformation ReadAdditionalLayerInformation(PSDFile psd, Stream stream)
{
var ali = new PSDAdditionalLayerInformation();
string signature = stream.ReadUsAsciiString(4);
if (signature != AdditionalLayerInfoSignature && signature != AdditionalLayerInfoSignature2)
{
throw new PSDFormatException($"unknown additional layer information signature \"{signature}\", expected \"{AdditionalLayerInfoSignature}\" or \"{AdditionalLayerInfoSignature2}\"");
}
string key = stream.ReadUsAsciiString(4);
bool length64Bit = false;
if (key == "Layr" || key == "Lr16" || key == "Lr32")
{
// layer info has been shunted in here instead of where it belongs
ReadLayerInformation(psd, stream, roundToFourBytes: true);
return(null);
}
if (psd.Version == 2)
{
// some keys have 64-bit lengths
length64Bit =
(key == "LMsk") ||
(key == "Mt16") ||
(key == "Mt32") ||
(key == "Mtrn") ||
(key == "Alph") ||
(key == "FMsk") ||
(key == "Ink2") ||
(key == "FEid") ||
(key == "FXid") ||
(key == "PxSD")
;
}
long length = length64Bit
? stream.ReadBigEndianInt64()
: stream.ReadBigEndianInt32();
byte[] data = stream.ReadBytes((int)length);
ali.Key = key;
ali.Data = data;
// round up to 4 bytes
// WARNING: spec is a liar; says "rounded up to an even byte count"
if (length % 4 != 0)
{
var skipCount = (int)(4 - (length % 4));
stream.ReadBytes(skipCount);
}
return(ali);
}
/// <summary>
/// Reads a layer record from a stream and populates a PSD layer object with the information.
/// </summary>
/// <param name="psd">
/// The PSD file being read. Used to obtain the file format version and to populate the
/// <see cref="PSDFile.Layers"/> array if general layer information has been "outsourced" to an additional
/// layer information block.
/// </param>
/// <param name="layer">The layer to populate with information read from the stream.</param>
/// <param name="stream">The stream from which to read layer information.</param>
public static void ReadLayerRecord(PSDFile psd, PSDLayer layer, Stream stream)
{
layer.Top = stream.ReadBigEndianInt32();
layer.Left = stream.ReadBigEndianInt32();
layer.Bottom = stream.ReadBigEndianInt32();
layer.Right = stream.ReadBigEndianInt32();
short numberChannels = stream.ReadBigEndianInt16();
layer.Channels = new PSDLayerChannel[numberChannels];
for (int i = 0; i < numberChannels; ++i)
{
var channel = new PSDLayerChannel();
channel.ID = stream.ReadBigEndianInt16();
channel.DataLength = (psd.Version == 2)
? stream.ReadBigEndianInt64()
: stream.ReadBigEndianInt32();
layer.Channels[i] = channel;
}
string blendModeSignature = stream.ReadUsAsciiString(4);
if (blendModeSignature != BlendModeSignature)
{
throw new PSDFormatException($"expected blend mode signature \"{BlendModeSignature}\", got \"{blendModeSignature}\"");
}
int blendModeValue = stream.ReadBigEndianInt32();
if (!Enum.IsDefined(typeof(BlendMode), blendModeValue))
{
char[] blendModeChars =
{
(char)((blendModeValue >> 24) & 0xFF),
(char)((blendModeValue >> 16) & 0xFF),
(char)((blendModeValue >> 8) & 0xFF),
(char)((blendModeValue >> 0) & 0xFF)
};
string blendModeString = new string(blendModeChars);
throw new PSDFormatException($"invalid blend mode {blendModeValue} (\"{blendModeString}\")");
}
layer.BlendMode = (BlendMode)blendModeValue;
byte opacity = stream.ReadByteOrThrow();
layer.Opacity = opacity;
byte clipping = stream.ReadByteOrThrow();
if (clipping > 1)
{
throw new PSDFormatException($"invalid clipping value {clipping}; expected 0 (base) or 1 (non-base)");
}
layer.NonBaseClipping = (clipping == 1);
byte flags = stream.ReadByteOrThrow();
if ((flags & 0x01) != 0)
{
layer.TransparencyProtected = true;
}
if ((flags & 0x02) != 0)
{
layer.Visible = true;
}
if ((flags & 0x04) != 0)
{
layer.Obsolete = true;
}
if ((flags & 0x18) == 0x18)
{
// (both bits 3 and 4 must be set)
layer.PixelDataIrrelevantToDocumentAppearance = true;
}
// filler
stream.ReadByteOrThrow();
int extraDataLength = stream.ReadBigEndianInt32();
long extraDataStart = stream.Position;
ReadLayerMask(layer, stream);
ReadLayerBlendingRanges(layer, stream);
byte layerNameLength = stream.ReadByteOrThrow();
layer.Name = stream.ReadWindows1252String(layerNameLength);
int padTo4Bytes = 4 - ((layerNameLength + 1) % 4);
if (padTo4Bytes != 4) // there is zero padding if == 4
{
stream.ReadBytes(padTo4Bytes);
}
layer.AdditionalInformation = new List <PSDAdditionalLayerInformation>();
while (stream.Position < extraDataStart + extraDataLength)
{
PSDAdditionalLayerInformation pali = PSDFile.Reading.ReadAdditionalLayerInformation(psd, stream);
layer.AdditionalInformation.Add(pali);
}
}
