private void Read(Stream stream, bool metadataOnly)
{
Header = GifHeader.ReadHeader(stream);
if (Header.LogicalScreenDescriptor.HasGlobalColorTable)
{
GifHelpers.ReadColorTable(stream, Header.LogicalScreenDescriptor.GlobalColorTableSize);
}
ReadFrames(stream, metadataOnly);
var netscapeExtension =
Extensions
.OfType <GifApplicationExtension>()
.FirstOrDefault(GifHelpers.IsNetscapeExtension);
if (netscapeExtension != null)
{
RepeatCount = GifHelpers.GetRepeatCount(netscapeExtension);
}
else
{
RepeatCount = 1;
}
}
private void Read(Stream stream, IEnumerable <GifExtension> controlExtensions, bool metadataOnly)
{
// Note: at this point, the label (0x01) has already been read
byte[] bytes = new byte[13];
stream.ReadAll(bytes, 0, bytes.Length);
BlockSize = bytes[0];
if (BlockSize != 12)
{
throw GifHelpers.InvalidBlockSizeException("Plain Text Extension", 12, BlockSize);
}
Left = BitConverter.ToUInt16(bytes, 1);
Top = BitConverter.ToUInt16(bytes, 3);
Width = BitConverter.ToUInt16(bytes, 5);
Height = BitConverter.ToUInt16(bytes, 7);
CellWidth = bytes[9];
CellHeight = bytes[10];
ForegroundColorIndex = bytes[11];
BackgroundColorIndex = bytes[12];
var dataBytes = GifHelpers.ReadDataBlocks(stream, metadataOnly);
Text = Encoding.ASCII.GetString(dataBytes);
Extensions = controlExtensions.ToList().AsReadOnly();
}
internal static GifExtension ReadExtension(Stream stream, IEnumerable <GifExtension> controlExtensions,
bool metadataOnly)
{
// Note: at this point, the Extension Introducer (0x21) has already been read
var label = stream.ReadByte();
if (label < 0)
{
throw GifHelpers.UnexpectedEndOfStreamException();
}
switch (label)
{
case GifGraphicControlExtension.ExtensionLabel:
return(GifGraphicControlExtension.ReadGraphicsControl(stream));
case GifCommentExtension.ExtensionLabel:
return(GifCommentExtension.ReadComment(stream));
case GifPlainTextExtension.ExtensionLabel:
return(GifPlainTextExtension.ReadPlainText(stream, controlExtensions, metadataOnly));
case GifApplicationExtension.ExtensionLabel:
return(GifApplicationExtension.ReadApplication(stream));
default:
throw GifHelpers.UnknownExtensionTypeException(label);
}
}
private void Read(Stream stream)
{
// Note: at this point, the label (0xFE) has already been read
var bytes = GifHelpers.ReadDataBlocks(stream, false);
if (bytes != null)
{
Text = Encoding.ASCII.GetString(bytes);
}
}
private void Read(Stream stream, IEnumerable <GifExtension> controlExtensions, bool metadataOnly)
{
// Note: at this point, the Image Separator (0x2C) has already been read
Descriptor = GifImageDescriptor.ReadImageDescriptor(stream);
if (Descriptor.HasLocalColorTable)
{
GifHelpers.ReadColorTable(stream, Descriptor.LocalColorTableSize);
}
GifImageData.ReadImageData(stream, metadataOnly);
Extensions = controlExtensions.ToList().AsReadOnly();
}
private void Read(Stream stream)
{
Signature = GifHelpers.ReadString(stream, 3);
if (Signature != "GIF")
{
throw GifHelpers.InvalidSignatureException(Signature);
}
Version = GifHelpers.ReadString(stream, 3);
if (Version != "87a" && Version != "89a")
{
throw GifHelpers.UnsupportedVersionException(Version);
}
LogicalScreenDescriptor = GifLogicalScreenDescriptor.ReadLogicalScreenDescriptor(stream);
}
private void Read(Stream stream)
{
// Note: at this point, the label (0xFF) has already been read
byte[] bytes = new byte[12];
stream.ReadAll(bytes, 0, bytes.Length);
BlockSize = bytes[0]; // should always be 11
if (BlockSize != 11)
{
throw GifHelpers.InvalidBlockSizeException("Application Extension", 11, BlockSize);
}
ApplicationIdentifier = Encoding.ASCII.GetString(bytes, 1, 8);
byte[] authCode = new byte[3];
Array.Copy(bytes, 9, authCode, 0, 3);
AuthenticationCode = authCode;
Data = GifHelpers.ReadDataBlocks(stream, false);
}
private void Read(Stream stream)
{
// Note: at this point, the label (0xF9) has already been read
var bytes = new byte[6];
stream.ReadAll(bytes, 0, bytes.Length);
BlockSize = bytes[0]; // should always be 4
if (BlockSize != 4)
{
throw GifHelpers.InvalidBlockSizeException("Graphic Control Extension", 4, BlockSize);
}
var packedFields = bytes[1];
DisposalMethod = (packedFields & 0x1C) >> 2;
UserInput = (packedFields & 0x02) != 0;
HasTransparency = (packedFields & 0x01) != 0;
Delay = BitConverter.ToUInt16(bytes, 2) * 10; // milliseconds
TransparencyIndex = bytes[4];
}
internal static GifBlock ReadBlock(Stream stream, IEnumerable <GifExtension> controlExtensions,
bool metadataOnly)
{
var blockId = stream.ReadByte();
if (blockId < 0)
{
throw GifHelpers.UnexpectedEndOfStreamException();
}
switch (blockId)
{
case GifExtension.ExtensionIntroducer:
return(GifExtension.ReadExtension(stream, controlExtensions, metadataOnly));
case GifFrame.ImageSeparator:
return(GifFrame.ReadFrame(stream, controlExtensions, metadataOnly));
case GifTrailer.TrailerByte:
return(GifTrailer.ReadTrailer());
default:
throw GifHelpers.UnknownBlockTypeException(blockId);
}
}
private void Read(Stream stream, bool metadataOnly)
{
LzwMinimumCodeSize = (byte)stream.ReadByte();
CompressedData = GifHelpers.ReadDataBlocks(stream, metadataOnly);
}
