imagesize/formats/
jpeg.rs

1use crate::util::*;
2use crate::{ImageError, ImageResult, ImageSize};
3
4use std::io::{BufRead, Seek, SeekFrom};
5
6pub fn size<R: BufRead + Seek>(reader: &mut R) -> ImageResult<ImageSize> {
7    let mut marker = [0; 2];
8    let mut depth = 0i32;
9
10    //  Go to the first tag after FF D8
11    reader.seek(SeekFrom::Start(2))?;
12
13    loop {
14        //  Read current marker (FF XX)
15        reader.read_exact(&mut marker)?;
16
17        if marker[0] != 0xFF {
18            //  Did not read a marker. Assume image is corrupt.
19            return Err(ImageError::CorruptedImage);
20        }
21
22        let page = marker[1];
23
24        //  Check for valid SOFn markers. C4, C8, and CC aren't dimension markers.
25        if (0xC0..=0xC3).contains(&page)
26            || (0xC5..=0xC7).contains(&page)
27            || (0xC9..=0xCB).contains(&page)
28            || (0xCD..=0xCF).contains(&page)
29        {
30            //  Only get outside image size
31            if depth == 0 {
32                //  Correct marker, go forward 3 bytes so we're at height offset
33                reader.seek(SeekFrom::Current(3))?;
34                break;
35            }
36        } else if page == 0xD8 {
37            depth += 1;
38        } else if page == 0xD9 {
39            depth -= 1;
40            if depth < 0 {
41                return Err(ImageError::CorruptedImage);
42            }
43        }
44
45        //  Read the marker length and skip over it entirely
46        let page_size = read_u16(reader, &Endian::Big)? as i64;
47        reader.seek(SeekFrom::Current(page_size - 2))?;
48    }
49
50    Ok(ImageSize {
51        height: read_u16(reader, &Endian::Big)? as usize,
52        width: read_u16(reader, &Endian::Big)? as usize,
53    })
54}
55
56pub fn matches(header: &[u8]) -> bool {
57    header.starts_with(b"\xFF\xD8\xFF")
58}