234 lines
8.9 KiB
Rust
234 lines
8.9 KiB
Rust
//
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// Copyright (c) 2017 KAMADA Ken'ichi.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// 1. Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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//
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use std::collections::HashMap;
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use std::io;
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use std::io::Read;
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use crate::error::Error;
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use crate::isobmff;
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use crate::jpeg;
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use crate::tag::Tag;
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use crate::tiff;
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use crate::tiff::{Field, IfdEntry, In, ProvideUnit};
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/// The `Reader` struct reads a JPEG or TIFF image,
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/// parses the Exif attributes in it, and holds the results.
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///
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/// # Examples
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/// ```
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/// use exif::{In, Reader, Tag};
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/// let file = std::fs::File::open("tests/exif.jpg").unwrap();
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/// let reader = Reader::new(&mut std::io::BufReader::new(&file)).unwrap();
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/// let xres = reader.get_field(Tag::XResolution, In::PRIMARY).unwrap();
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/// assert_eq!(xres.display_value().with_unit(&reader).to_string(),
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/// "72 pixels per inch");
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/// ```
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//
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// The struct Reader is self-contained, which means that it does not
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// have any external reference. The `fields` field actually refers to
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// the `buf` field. The type system of the current Rust (as of 1.15)
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// cannot represent this, so the static lifetime is used to trick it.
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//
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// This struct can be moved because the contents of a Vec are allocated
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// in the heap and do not change their addresses by the move.
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//
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// The static lifetime is a lie and it must be kept secret in this struct.
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// - This struct must not be destructured by the users.
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// - The `fields` must be adjusted to refer the struct itself when
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// returned to the outside world.
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pub struct Reader {
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// TIFF data.
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buf: Vec<u8>,
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// Exif fields. Vec is used to keep the ability to enumerate all fields
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// even if there are duplicates.
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entries: Vec<IfdEntry>,
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// HashMap to the index of the Vec for faster random access.
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entry_map: HashMap<(In, Tag), usize>,
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// True if the TIFF data is little endian.
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little_endian: bool,
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}
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impl Reader {
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/// Reads a JPEG or TIFF image and parses the Exif attributes in it.
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/// If an error occurred, `exif::Error` is returned.
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pub fn new<R>(reader: &mut R)
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-> Result<Reader, Error> where R: io::BufRead {
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// Parse the data.
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let mut buf = Vec::new();
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reader.by_ref().take(4).read_to_end(&mut buf)?;
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if jpeg::is_jpeg(&buf) {
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let exif_buf = jpeg::get_exif_attr(
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&mut buf.as_mut_slice().chain(reader))?;
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buf = exif_buf;
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} else if tiff::is_tiff(&buf) {
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reader.read_to_end(&mut buf)?;
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} else {
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return Err(Error::InvalidFormat("Unknown image format"));
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}
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let (entries, le) = tiff::parse_exif(&buf)?;
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let entry_map = entries.iter().enumerate()
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.map(|(i, e)| (e.ifd_num_tag(), i)).collect();
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Ok(Reader {
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buf: buf,
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entries: entries,
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entry_map: entry_map,
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little_endian: le,
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})
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}
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/// Reads an image file and parses the Exif attributes in it.
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/// If an error occurred, `exif::Error` is returned.
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///
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/// Supported formats are HEIF, JPEG, and TIFF.
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///
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/// This method is provided for the convenience even though
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/// parsing containers is basically out of the scope of this library.
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pub fn read_from_container<R>(reader: &mut R) -> Result<Reader, Error>
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where R: io::BufRead + io::Seek {
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let mut buf = Vec::new();
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reader.by_ref().take(4096).read_to_end(&mut buf)?;
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if tiff::is_tiff(&buf) {
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reader.read_to_end(&mut buf)?;
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} else if jpeg::is_jpeg(&buf) {
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buf = jpeg::get_exif_attr(&mut buf.chain(reader))?;
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} else if isobmff::is_heif(&buf) {
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reader.seek(io::SeekFrom::Start(0))?;
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buf = isobmff::get_exif_attr(reader)?;
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} else {
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return Err(Error::InvalidFormat("Unknown image format"));
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}
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let (entries, le) = tiff::parse_exif(&buf)?;
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let entry_map = entries.iter().enumerate()
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.map(|(i, e)| (e.ifd_num_tag(), i)).collect();
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Ok(Reader {
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buf: buf,
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entries: entries,
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entry_map: entry_map,
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little_endian: le,
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})
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}
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/// Returns the slice that contains the TIFF data.
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#[inline]
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pub fn buf(&self) -> &[u8] {
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&self.buf[..]
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}
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/// Returns a slice of Exif fields.
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#[inline]
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pub fn fields(&self) -> impl ExactSizeIterator<Item = &Field> {
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self.entries.iter()
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.map(move |e| e.ref_field(&self.buf, self.little_endian))
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}
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/// Returns true if the TIFF data is in the little-endian byte order.
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#[inline]
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pub fn little_endian(&self) -> bool {
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self.little_endian
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}
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/// Returns a reference to the Exif field specified by the tag
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/// and the IFD number.
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#[inline]
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pub fn get_field(&self, tag: Tag, ifd_num: In) -> Option<&Field> {
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self.entry_map.get(&(ifd_num, tag))
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.map(|&i| self.entries[i].ref_field(&self.buf, self.little_endian))
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}
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}
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impl<'a> ProvideUnit<'a> for &'a Reader {
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fn get_field(self, tag: Tag, ifd_num: In) -> Option<&'a Field> {
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self.get_field(tag, ifd_num)
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}
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}
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#[cfg(test)]
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mod tests {
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use std::fs::File;
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use std::io::BufReader;
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use crate::value::Value;
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use super::*;
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#[test]
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fn get_field() {
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let file = File::open("tests/yaminabe.tif").unwrap();
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let reader = Reader::new(&mut BufReader::new(&file)).unwrap();
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match reader.get_field(Tag::ImageDescription, In(0)).unwrap().value {
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Value::Ascii(ref vec) => assert_eq!(vec, &[b"Test image"]),
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ref v => panic!("wrong variant {:?}", v)
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}
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match reader.get_field(Tag::ImageDescription, In(1)).unwrap().value {
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Value::Ascii(ref vec) => assert_eq!(vec, &[b"Test thumbnail"]),
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ref v => panic!("wrong variant {:?}", v)
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}
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match reader.get_field(Tag::ImageDescription, In(2)).unwrap().value {
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Value::Ascii(ref vec) => assert_eq!(vec, &[b"Test 2nd IFD"]),
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ref v => panic!("wrong variant {:?}", v)
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}
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}
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#[test]
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fn display_value_with_unit() {
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let file = File::open("tests/yaminabe.tif").unwrap();
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let reader = Reader::new(&mut BufReader::new(&file)).unwrap();
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// No unit.
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let exifver = reader.get_field(Tag::ExifVersion, In::PRIMARY).unwrap();
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assert_eq!(exifver.display_value().with_unit(&reader).to_string(),
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"2.31");
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// Fixed string.
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let width = reader.get_field(Tag::ImageWidth, In::PRIMARY).unwrap();
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assert_eq!(width.display_value().with_unit(&reader).to_string(),
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"17 pixels");
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// Unit tag (with a non-default value).
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let gpsalt = reader.get_field(Tag::GPSAltitude, In::PRIMARY).unwrap();
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assert_eq!(gpsalt.display_value().with_unit(&reader).to_string(),
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"0.5 meters below sea level");
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// Unit tag is missing but the default is specified.
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let xres = reader.get_field(Tag::XResolution, In::PRIMARY).unwrap();
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assert_eq!(xres.display_value().with_unit(&reader).to_string(),
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"72 pixels per inch");
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// Unit tag is missing and the default is not specified.
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let gpslat = reader.get_field(Tag::GPSLatitude, In::PRIMARY).unwrap();
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assert_eq!(gpslat.display_value().with_unit(&reader).to_string(),
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"10 deg 0 min 0 sec [GPSLatitudeRef missing]");
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}
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#[test]
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fn heif() {
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let file = std::fs::File::open("tests/exif.heic").unwrap();
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let reader = Reader::read_from_container(
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&mut std::io::BufReader::new(&file)).unwrap();
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assert_eq!(reader.fields().len(), 2);
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let exifver = reader.get_field(Tag::ExifVersion, In::PRIMARY).unwrap();
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assert_eq!(exifver.display_value().to_string(), "2.31");
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}
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}
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