Support decoding WEBPs in extended format

src/webp/decoder.rs

@@ -60,25 +60,39 @@ impl<R: Read> WebPDecoder<R> {
  Ok(size)
  }
 
- fn read_vp8_header(&mut self) -> ImageResult<()> {
- let mut vp8 = Vec::with_capacity(4);
- self.r.by_ref().take(4).read_to_end(&mut vp8)?;
-
- if &*vp8 != b"VP8 " {
- return Err(ImageError::Decoding(DecodingError::with_message(
- ImageFormat::WebP.into(),
- "Invalid VP8 signature.".to_string(),
- )));
+ fn read_vp8_header(&mut self) -> ImageResult<u32> {
+ loop {
+ let mut chunk = Vec::with_capacity(4);
+ self.r.by_ref().take(4).read_to_end(&mut chunk)?;
+
+ match &*chunk {
+ b"VP8 " => {
+ let len = self.r.read_u32::<LittleEndian>()?;
+ return Ok(len);
+ }
+ b"ALPH" | b"VP8L" | b"ANIM" | b"ANMF" => {
+ // Alpha, Lossless and Animation isn't supported
+ return Err(ImageError::Decoding(DecodingError::with_message(
+ ImageFormat::WebP.into(),
+ "Unsupported WEBP feature.".to_string(),
+ )));
+ }
+ _ => {
+ let mut len = self.r.read_u32::<LittleEndian>()?;
+ if len % 2 != 0 {
+ // RIFF chunks containing an uneven number of bytes append
+ // an extra 0x00 at the end of the chunk
+ len += 1;
+ }
+ io::copy(&mut self.r.by_ref().take(len as u64), &mut io::sink())?;
+ }
+ }
  }
-
- let _len = self.r.read_u32::<LittleEndian>()?;
-
- Ok(())
  }
 
- fn read_frame(&mut self) -> ImageResult<()> {
+ fn read_frame(&mut self, len: u32) -> ImageResult<()> {
  let mut framedata = Vec::new();
- self.r.read_to_end(&mut framedata)?;
+ self.r.by_ref().take(len as u64).read_to_end(&mut framedata)?;
  let m = io::Cursor::new(framedata);
 
  let mut v = Vp8Decoder::new(m);
@@ -92,8 +106,8 @@ impl<R: Read> WebPDecoder<R> {
  fn read_metadata(&mut self) -> ImageResult<()> {
  if !self.have_frame {
  self.read_riff_header()?;
- self.read_vp8_header()?;
- self.read_frame()?;
+ let len = self.read_vp8_header()?;
+ self.read_frame(len)?;
 
  self.have_frame = true;
  }