public void ProcessChunk(string fourCc, byte[] payload)
{
switch (fourCc)
{
case "EXIF":
{
// We have seen WebP images with and without the preamble here. It's likely that some software incorrectly
// copied an entire JPEG segment into the WebP image. Regardless, we can handle it here.
var reader = ExifReader.StartsWithJpegExifPreamble(payload)
? new ByteArrayReader(payload, ExifReader.JpegSegmentPreambleLength)
: new ByteArrayReader(payload);
_directories.AddRange(new ExifReader().Extract(reader));
break;
}
case "ICCP":
{
_directories.Add(new IccReader().Extract(new ByteArrayReader(payload)));
break;
}
case "XMP ":
{
_directories.Add(new XmpReader().Extract(payload));
break;
}
case "VP8X":
{
if (payload.Length != 10)
{
break;
}
string?error = null;
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
var isAnimation = false;
var hasAlpha = false;
var widthMinusOne = -1;
var heightMinusOne = -1;
try
{
// Flags
// bit 0: has fragments
// bit 1: is animation
// bit 2: has XMP
// bit 3: has Exif
// bit 4: has alpha
// big 5: has ICC
isAnimation = reader.GetBit(1);
hasAlpha = reader.GetBit(4);
// Image size
widthMinusOne = reader.GetInt24(4);
heightMinusOne = reader.GetInt24(7);
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8X' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, widthMinusOne + 1);
directory.Set(WebPDirectory.TagImageHeight, heightMinusOne + 1);
directory.Set(WebPDirectory.TagHasAlpha, hasAlpha);
directory.Set(WebPDirectory.TagIsAnimation, isAnimation);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
case "VP8L":
{
if (payload.Length < 5)
{
break;
}
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
string?error = null;
var widthMinusOne = -1;
var heightMinusOne = -1;
try
{
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#2_riff_header
// Expect the signature byte
if (reader.GetByte(0) != 0x2F)
{
break;
}
var b1 = reader.GetByte(1);
var b2 = reader.GetByte(2);
var b3 = reader.GetByte(3);
var b4 = reader.GetByte(4);
// 14 bits for width
widthMinusOne = (b2 & 0x3F) << 8 | b1;
// 14 bits for height
heightMinusOne = (b4 & 0x0F) << 10 | b3 << 2 | (b2 & 0xC0) >> 6;
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8L' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, widthMinusOne + 1);
directory.Set(WebPDirectory.TagImageHeight, heightMinusOne + 1);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
case "VP8 ":
{
if (payload.Length < 10)
{
break;
}
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
string?error = null;
var width = 0;
var height = 0;
try
{
// https://tools.ietf.org/html/rfc6386#section-9.1
// https://github.com/webmproject/libwebp/blob/master/src/enc/syntax.c#L115
// Expect the signature bytes
if (reader.GetByte(3) != 0x9D ||
reader.GetByte(4) != 0x01 ||
reader.GetByte(5) != 0x2A)
{
break;
}
width = reader.GetUInt16(6);
height = reader.GetUInt16(8);
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, width);
directory.Set(WebPDirectory.TagImageHeight, height);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
}
}
public void ProcessChunk(string fourCc, byte[] payload)
{
switch (fourCc)
{
case "EXIF":
{
_directories.AddRange(new ExifReader().Extract(new ByteArrayReader(payload)));
break;
}
case "ICCP":
{
_directories.Add(new IccReader().Extract(new ByteArrayReader(payload)));
break;
}
case "XMP ":
{
_directories.Add(new XmpReader().Extract(payload));
break;
}
case "VP8X":
{
if (payload.Length != 10)
{
break;
}
string error = null;
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
var isAnimation = false;
var hasAlpha = false;
var widthMinusOne = -1;
var heightMinusOne = -1;
try
{
// Flags
// var hasFragments = reader.GetBit(0);
isAnimation = reader.GetBit(1);
// var hasXmp = reader.GetBit(2);
// var hasExif = reader.GetBit(3);
hasAlpha = reader.GetBit(4);
// var hasIcc = reader.GetBit(5);
// Image size
widthMinusOne = reader.GetInt24(4);
heightMinusOne = reader.GetInt24(7);
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8X' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, widthMinusOne + 1);
directory.Set(WebPDirectory.TagImageHeight, heightMinusOne + 1);
directory.Set(WebPDirectory.TagHasAlpha, hasAlpha);
directory.Set(WebPDirectory.TagIsAnimation, isAnimation);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
case "VP8L":
{
if (payload.Length < 5)
{
break;
}
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
string error = null;
var widthMinusOne = -1;
var heightMinusOne = -1;
try
{
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#2_riff_header
// Expect the signature byte
if (reader.GetByte(0) != 0x2F)
{
break;
}
var b1 = reader.GetByte(1);
var b2 = reader.GetByte(2);
var b3 = reader.GetByte(3);
var b4 = reader.GetByte(4);
// 14 bits for width
widthMinusOne = (b2 & 0x3F) << 8 | b1;
// 14 bits for height
heightMinusOne = (b4 & 0x0F) << 10 | b3 << 2 | (b2 & 0xC0) >> 6;
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8L' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, widthMinusOne + 1);
directory.Set(WebPDirectory.TagImageHeight, heightMinusOne + 1);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
case "VP8 ":
{
if (payload.Length < 10)
{
break;
}
var reader = new ByteArrayReader(payload, isMotorolaByteOrder: false);
string error = null;
var width = 0;
var height = 0;
try
{
// https://tools.ietf.org/html/rfc6386#section-9.1
// https://github.com/webmproject/libwebp/blob/master/src/enc/syntax.c#L115
// Expect the signature bytes
if (reader.GetByte(3) != 0x9D ||
reader.GetByte(4) != 0x01 ||
reader.GetByte(5) != 0x2A)
{
break;
}
width = reader.GetUInt16(6);
height = reader.GetUInt16(8);
}
catch (IOException e)
{
error = "Exception reading WebpRiff chunk 'VP8' : " + e.Message;
}
var directory = new WebPDirectory();
if (error == null)
{
directory.Set(WebPDirectory.TagImageWidth, width);
directory.Set(WebPDirectory.TagImageHeight, height);
}
else
{
directory.AddError(error);
}
_directories.Add(directory);
break;
}
}
}