public static long FindChunk(Stream stream, string chunk)
{
long found_offset = -1;
var file = new ArcView.Reader(stream);
try
{
char[] buf = new char[4];
file.BaseStream.Position = 8;
while (-1 != file.PeekChar())
{
long chunk_offset = file.BaseStream.Position;
uint chunk_size = Binary.BigEndian(file.ReadUInt32());
if (4 != file.Read(buf, 0, 4))
{
break;
}
if (chunk.SequenceEqual(buf))
{
found_offset = chunk_offset;
break;
}
file.BaseStream.Position += chunk_size + 4;
}
}
catch
{
// ignore errors
}
finally
{
file.Dispose();
}
return(found_offset);
}
public override ImageMetaData ReadMetaData(Stream stream)
{
ImageMetaData meta = null;
var file = new ArcView.Reader(stream);
try
{
file.ReadUInt32();
if (file.ReadUInt32() != 0x0a1a0a0d)
{
return(null);
}
uint chunk_size = Binary.BigEndian(file.ReadUInt32());
char[] chunk_type = new char[4];
file.Read(chunk_type, 0, 4);
if (!chunk_type.SequenceEqual("IHDR"))
{
return(null);
}
meta = new ImageMetaData();
meta.Width = Binary.BigEndian(file.ReadUInt32());
meta.Height = Binary.BigEndian(file.ReadUInt32());
int bpp = file.ReadByte();
int color_type = file.ReadByte();
switch (color_type)
{
case 2: meta.BPP = bpp * 3; break;
case 3: meta.BPP = 24; break;
case 4: meta.BPP = bpp * 2; break;
case 6: meta.BPP = bpp * 4; break;
default: meta.BPP = bpp; break;
}
SkipBytes(file, 7);
for (;;)
{
chunk_size = Binary.BigEndian(file.ReadUInt32());
file.Read(chunk_type, 0, 4);
if (chunk_type.SequenceEqual("IDAT") || chunk_type.SequenceEqual("IEND"))
{
break;
}
if (chunk_type.SequenceEqual("oFFs"))
{
int x = Binary.BigEndian(file.ReadInt32());
int y = Binary.BigEndian(file.ReadInt32());
if (0 == file.ReadByte())
{
meta.OffsetX = x;
meta.OffsetY = y;
}
break;
}
SkipBytes(file, chunk_size + 4);
}
}
catch
{
meta = null;
}
finally
{
file.Dispose();
if (stream.CanSeek)
{
stream.Position = 0;
}
}
return(meta);
}