public override ImageMetaData ReadMetaData(Stream stream)
{
if (0x46464952 != FormatCatalog.ReadSignature (stream)) // 'RIFF'
return null;
var header = new byte[0x10];
if (8 != stream.Read (header, 0, 8))
return null;
if (!Binary.AsciiEqual (header, 4, "WEBP"))
return null;
bool found_vp8x = false;
var info = new WebPMetaData();
int chunk_size;
for (;;)
{
if (8 != stream.Read (header, 0, 8))
return null;
chunk_size = LittleEndian.ToInt32 (header, 4);
int aligned_size = (chunk_size + 1) & ~1;
if (!found_vp8x && Binary.AsciiEqual (header, 0, "VP8X"))
{
found_vp8x = true;
if (chunk_size < 10)
return null;
if (chunk_size > header.Length)
header = new byte[chunk_size];
if (chunk_size != stream.Read (header, 0, chunk_size))
return null;
info.Flags = (WebPFeature)LittleEndian.ToUInt32 (header, 0);
info.Width = 1 + GetUInt24 (header, 4);
info.Height = 1 + GetUInt24 (header, 7);
if ((long)info.Width * info.Height >= (1L << 32))
return null;
continue;
}
if (Binary.AsciiEqual (header, 0, "VP8 ") || Binary.AsciiEqual (header, 0, "VP8L"))
{
info.IsLossless = header[3] == 'L';
info.DataOffset = stream.Position;
info.DataSize = chunk_size;
if (!found_vp8x)
{
if (chunk_size < 10 || 10 != stream.Read (header, 0, 10))
return null;
if (header[3] != 0x9D || header[4] != 1 || header[5] != 0x2A)
return null;
if (0 != (header[0] & 1)) // not a keyframe
return null;
info.Width = LittleEndian.ToUInt16 (header, 6) & 0x3FFFu;
info.Height = LittleEndian.ToUInt16 (header, 8) & 0x3FFFu;
}
break;
}
if (Binary.AsciiEqual (header, 0, "ALPH"))
{
info.AlphaOffset = stream.Position;
info.AlphaSize = chunk_size;
}
stream.Seek (aligned_size, SeekOrigin.Current);
}
if (0 == info.Width || 0 == info.Height)
return null;
return info;
}
public WebPDecoder(Stream input, WebPMetaData info)
{
m_input = new ArcView.Reader (input);
m_info = info;
m_stride = (int)info.Width * 4;
m_output = new byte[m_stride * (int)info.Height];
m_io = new VP8Io();
if (0 != m_info.AlphaOffset)
{
m_input.BaseStream.Position = m_info.AlphaOffset;
m_alpha_data = m_input.ReadBytes (m_info.AlphaSize);
m_alpha_plane = new byte[info.Width * info.Height];
Format = PixelFormats.Bgra32;
}
else
{
Format = PixelFormats.Bgr32;
}
}
public override ImageMetaData ReadMetaData(IBinaryStream stream)
{
if (0x46464952 != stream.Signature) // 'RIFF'
{
return(null);
}
if (!stream.ReadHeader(12).AsciiEqual(8, "WEBP"))
{
return(null);
}
var header = new byte[0x10];
bool found_vp8x = false;
var info = new WebPMetaData {
BPP = 32
};
int chunk_size;
for (;;)
{
if (8 != stream.Read(header, 0, 8))
{
return(null);
}
chunk_size = LittleEndian.ToInt32(header, 4);
int aligned_size = (chunk_size + 1) & ~1;
if (!found_vp8x && Binary.AsciiEqual(header, 0, "VP8X"))
{
found_vp8x = true;
if (chunk_size < 10)
{
return(null);
}
if (chunk_size > header.Length)
{
header = new byte[chunk_size];
}
if (chunk_size != stream.Read(header, 0, chunk_size))
{
return(null);
}
info.Flags = (WebPFeature)LittleEndian.ToUInt32(header, 0);
info.Width = 1 + (uint)header.ToInt24(4);
info.Height = 1 + (uint)header.ToInt24(7);
if ((long)info.Width * info.Height >= (1L << 32))
{
return(null);
}
continue;
}
if (Binary.AsciiEqual(header, 0, "VP8 ") || Binary.AsciiEqual(header, 0, "VP8L"))
{
info.IsLossless = header[3] == 'L';
info.DataOffset = stream.Position;
info.DataSize = aligned_size;
if (!found_vp8x)
{
if (chunk_size < 10 || 10 != stream.Read(header, 0, 10))
{
return(null);
}
if (info.IsLossless)
{
if (header[0] != 0x2F || (header[4] >> 5) != 0)
{
return(null);
}
uint wh = LittleEndian.ToUInt32(header, 1);
info.Width = (wh & 0x3FFFu) + 1;
info.Height = ((wh >> 14) & 0x3FFFu) + 1;
info.HasAlpha = 0 != (header[4] & 0x10);
}
else
{
if (header[3] != 0x9D || header[4] != 1 || header[5] != 0x2A)
{
return(null);
}
if (0 != (header[0] & 1)) // not a keyframe
{
return(null);
}
info.Width = LittleEndian.ToUInt16(header, 6) & 0x3FFFu;
info.Height = LittleEndian.ToUInt16(header, 8) & 0x3FFFu;
}
}
break;
}
if (Binary.AsciiEqual(header, 0, "ALPH"))
{
info.AlphaOffset = stream.Position;
info.AlphaSize = chunk_size;
}
stream.Seek(aligned_size, SeekOrigin.Current);
}
if (0 == info.Width || 0 == info.Height)
{
return(null);
}
return(info);
}
