Merge pull request #206 from fintelia/simplify-jpeg

Simplify and avoid allocation in jpeg decompression

Author: fintelia

src/decoder/image.rs

@@ -1,5 +1,5 @@
 use super::ifd::{Directory, Value};
-use super::stream::{ByteOrder, DeflateReader, JpegReader, LZWReader, PackBitsReader};
+use super::stream::{ByteOrder, DeflateReader, LZWReader, PackBitsReader};
 use super::tag_reader::TagReader;
 use super::{fp_predict_f32, fp_predict_f64, DecodingBuffer, Limits};
 use super::{stream::SmartReader, ChunkType};
@@ -356,7 +356,7 @@ impl Image {
         photometric_interpretation: PhotometricInterpretation,
         compression_method: CompressionMethod,
         compressed_length: u64,
-        jpeg_tables: Option<Arc<Vec<u8>>>,
+        jpeg_tables: Option<&[u8]>,
     ) -> TiffResult<Box<dyn Read + 'r>> {
         Ok(match compression_method {
             CompressionMethod::None => Box::new(reader),
@@ -374,7 +374,29 @@ impl Image {
                     ));
                 }
 
-                let jpeg_reader = JpegReader::new(reader, compressed_length, jpeg_tables)?;
+                // Construct new jpeg_reader wrapping a SmartReader.
+                //
+                // JPEG compression in TIFF allows saving quantization and/or huffman tables in one
+                // central location. These `jpeg_tables` are simply prepended to the remaining jpeg image data.
+                // Because these `jpeg_tables` start with a `SOI` (HEX: `0xFFD8`) or __start of image__ marker
+                // which is also at the beginning of the remaining JPEG image data and would
+                // confuse the JPEG renderer, one of these has to be taken off. In this case the first two
+                // bytes of the remaining JPEG data is removed because it follows `jpeg_tables`.
+                // Similary, `jpeg_tables` ends with a `EOI` (HEX: `0xFFD9`) or __end of image__ marker,
+                // this has to be removed as well (last two bytes of `jpeg_tables`).
+                let jpeg_reader = match jpeg_tables {
+                    Some(jpeg_tables) => {
+                        let mut reader = reader.take(compressed_length);
+                        reader.read_exact(&mut [0; 2])?;
+
+                        Box::new(
+                            Cursor::new(&jpeg_tables[..jpeg_tables.len() - 2])
+                                .chain(reader.take(compressed_length)),
+                        ) as Box<dyn Read>
+                    }
+                    None => Box::new(reader.take(compressed_length)),
+                };
+
                 let mut decoder = jpeg::Decoder::new(jpeg_reader);
 
                 match photometric_interpretation {
@@ -582,13 +604,12 @@ impl Image {
 
         let padding_right = chunk_dims.0 - data_dims.0;
 
-        let jpeg_tables = self.jpeg_tables.clone();
         let mut reader = Self::create_reader(
             reader,
             photometric_interpretation,
             compression_method,
             *compressed_bytes,
-            jpeg_tables,
+            self.jpeg_tables.as_deref().map(|a| &**a),
         )?;
 
         if output_width == data_dims.0 as usize && padding_right == 0 {

src/decoder/stream.rs

@@ -1,8 +1,7 @@
 //! All IO functionality needed for TIFF decoding
 
 use std::convert::TryFrom;
-use std::io::{self, BufRead, BufReader, Read, Seek, SeekFrom, Take};
-use std::sync::Arc;
+use std::io::{self, BufRead, BufReader, Read, Seek, Take};
 
 /// Byte order of the TIFF file.
 #[derive(Clone, Copy, Debug)]
@@ -183,104 +182,6 @@ impl<R: Read> Read for LZWReader<R> {
     }
 }
 
-///
-/// ## JPEG Reader (for "new-style" JPEG format (TIFF compression tag 7))
-///
-
-pub(crate) struct JpegReader {
-    jpeg_tables: Option<Arc<Vec<u8>>>,
-
-    buffer: io::Cursor<Vec<u8>>,
-
-    offset: usize,
-}
-
-impl JpegReader {
-    /// Constructs new JpegReader wrapping a SmartReader.
-    /// Because JPEG compression in TIFF allows to save quantization and/or huffman tables in one
-    /// central location, the constructor accepts this data as `jpeg_tables` here containing either
-    /// or both.
-    /// These `jpeg_tables` are simply prepended to the remaining jpeg image data.
-    /// Because these `jpeg_tables` start with a `SOI` (HEX: `0xFFD8`) or __start of image__ marker
-    /// which is also at the beginning of the remaining JPEG image data and would
-    /// confuse the JPEG renderer, one of these has to be taken off. In this case the first two
-    /// bytes of the remaining JPEG data is removed because it follows `jpeg_tables`.
-    /// Similary, `jpeg_tables` ends with a `EOI` (HEX: `0xFFD9`) or __end of image__ marker,
-    /// this has to be removed as well (last two bytes of `jpeg_tables`).
-    pub fn new<R: Read>(
-        mut reader: R,
-        length: u64,
-        jpeg_tables: Option<Arc<Vec<u8>>>,
-    ) -> io::Result<JpegReader> {
-        // Read jpeg image data
-        let mut segment = vec![0; length as usize];
-
-        reader.read_exact(&mut segment[..])?;
-
-        match jpeg_tables {
-            Some(jpeg_tables) => {
-                assert!(
-                    jpeg_tables.len() >= 2,
-                    "jpeg_tables, if given, must be at least 2 bytes long. Got {:?}",
-                    jpeg_tables
-                );
-
-                assert!(
-                    length >= 2,
-                    "if jpeg_tables is given, length must be at least 2 bytes long, got {}",
-                    length
-                );
-
-                let mut buffer = io::Cursor::new(segment);
-                // Skip the first two bytes (marker bytes)
-                buffer.seek(SeekFrom::Start(2))?;
-
-                Ok(JpegReader {
-                    buffer,
-                    jpeg_tables: Some(jpeg_tables),
-                    offset: 0,
-                })
-            }
-            None => Ok(JpegReader {
-                buffer: io::Cursor::new(segment),
-                jpeg_tables: None,
-                offset: 0,
-            }),
-        }
-    }
-}
-
-impl Read for JpegReader {
-    // #[inline]
-    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        let mut start = 0;
-
-        if let Some(jpeg_tables) = &self.jpeg_tables {
-            if jpeg_tables.len() - 2 > self.offset {
-                // Read (rest of) jpeg_tables to buf (without the last two bytes)
-                let size_remaining = jpeg_tables.len() - self.offset - 2;
-                let to_copy = size_remaining.min(buf.len());
-
-                buf[start..start + to_copy]
-                    .copy_from_slice(&jpeg_tables[self.offset..self.offset + to_copy]);
-
-                self.offset += to_copy;
-
-                if to_copy == buf.len() {
-                    return Ok(to_copy);
-                }
-
-                start += to_copy;
-            }
-        }
-
-        let read = self.buffer.read(&mut buf[start..])?;
-        self.offset += read;
-
-        Ok(read + start)
-    }
-}
-
 ///
 /// ## PackBits Reader
 ///