mirror of
https://github.com/storytold/lightcraft.git
synced 2026-11-10 10:29:55 -06:00
Andrew FrahnandClaude Opus 5.5
fb097d61be
Mechanical rename right after the fork so upstream merges map cleanly. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
439 lines
19 KiB
Rust
439 lines
19 KiB
Rust
//! Embedded preview extraction: the largest baseline/progressive JPEG stored in a TIFF-based raw (IFD strips
|
|
//! with JPEG compression, `JPEGInterchangeFormat` pointers in any IFD, Nikon/others' maker-note preview IFDs),
|
|
//! or a DNG 1.7 JPEG XL preview IFD stored as a single tile/strip (a standalone `.jxl` file, as the spec
|
|
//! recommends for previews).
|
|
|
|
use dac_tiff::image::chunk_bytes;
|
|
use dac_tiff::tags as t;
|
|
use dac_tiff::{Ifd, Tiff, makernote};
|
|
|
|
/// Colour space of an embedded JPEG when the enclosing raw supplies it instead of the JPEG.
|
|
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
|
|
pub enum PreviewColorSpace {
|
|
Srgb,
|
|
AdobeRgb,
|
|
}
|
|
|
|
/// Nikon maker-note ColorSpace (0x001e: 1 = sRGB, 2 = Adobe RGB), per Nikon tag documentation.
|
|
/// This is a fallback only: a JPEG's own ICC/EXIF colour declaration takes precedence.
|
|
pub fn embedded_preview_color_space(bytes: &[u8]) -> Option<PreviewColorSpace> {
|
|
let tiff = Tiff::parse(bytes).ok()?;
|
|
let make = tiff.ifds.first()?.string(t::MAKE)?;
|
|
if !make.to_ascii_uppercase().starts_with("NIKON") {
|
|
return None;
|
|
}
|
|
let e = tiff.exif()?.get(t::MAKER_NOTE)?;
|
|
let mn = makernote::parse_makernote(bytes, e.offset, e.count() as u64, tiff.order, &make)?;
|
|
match mn.ifd.u16(0x001e)? {
|
|
1 => Some(PreviewColorSpace::Srgb),
|
|
2 => Some(PreviewColorSpace::AdobeRgb),
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
/// Whether `b` looks like a displayable (DCT) JPEG: SOI, and the first SOF marker is not lossless.
|
|
fn is_dct_jpeg(b: &[u8]) -> bool {
|
|
if b.len() < 4 || b[0] != 0xff || b[1] != 0xd8 {
|
|
return false;
|
|
}
|
|
let mut i = 2;
|
|
while i + 4 <= b.len() {
|
|
if b[i] != 0xff {
|
|
return false;
|
|
}
|
|
let m = b[i + 1];
|
|
if m == 0xff {
|
|
i += 1;
|
|
continue;
|
|
}
|
|
match m {
|
|
0xc0..=0xc2 => return true,
|
|
0xc3 | 0xc5..=0xc7 | 0xcb | 0xcd..=0xcf => return false,
|
|
0xda | 0xd9 => return false,
|
|
_ => {}
|
|
}
|
|
let len = u16::from_be_bytes([b[i + 2], b[i + 3]]) as usize;
|
|
i += 2 + len;
|
|
}
|
|
false
|
|
}
|
|
|
|
/// Whether `b` is a JPEG XL file: a bare codestream or the ISO-BMFF container's signature box.
|
|
fn is_jxl(b: &[u8]) -> bool {
|
|
b.starts_with(&[0xff, 0x0a]) || b.starts_with(&[0, 0, 0, 0x0c, b'J', b'X', b'L', b' ', 0x0d, 0x0a, 0x87, 0x0a])
|
|
}
|
|
|
|
fn candidates<'a>(data: &'a [u8], ifd: &Ifd, base: u64, out: &mut Vec<&'a [u8]>) {
|
|
// whole JPEG files stored as an undefined-type tag value (e.g. Panasonic `JpgFromRaw` 0x002e)
|
|
for e in &ifd.entries {
|
|
if matches!(e.value, dac_tiff::Value::Undefined(_))
|
|
&& e.count() > 1024
|
|
&& let Some(s) = data.get(e.offset as usize..(e.offset.saturating_add(e.count() as u64) as usize).min(data.len()))
|
|
&& s.starts_with(&[0xff, 0xd8])
|
|
{
|
|
out.push(s);
|
|
}
|
|
}
|
|
if let (Some(off), Some(len)) = (ifd.u64(t::JPEG_INTERCHANGE_FORMAT), ifd.u64(t::JPEG_INTERCHANGE_FORMAT_LENGTH)) {
|
|
let off = off.saturating_add(base);
|
|
if let Some(s) = data.get(off as usize..(off.saturating_add(len) as usize).min(data.len())) {
|
|
out.push(s);
|
|
}
|
|
}
|
|
if matches!(ifd.u16(t::COMPRESSION), Some(6) | Some(7) | Some(34892))
|
|
&& let Ok(info) = ifd.image()
|
|
{
|
|
let chunks = info.chunks(data.len() as u64);
|
|
if chunks.len() == 1
|
|
&& let Some(s) = chunk_bytes(data, &chunks[0])
|
|
{
|
|
out.push(s);
|
|
}
|
|
}
|
|
// a rendered (RGB or grey, never CFA/LinearRaw/mask) JPEG XL preview in one chunk
|
|
if ifd.u16(t::COMPRESSION) == Some(t::compression::JPEG_XL)
|
|
&& matches!(ifd.u16(t::PHOTOMETRIC), Some(t::photometric::BLACK_IS_ZERO | t::photometric::RGB))
|
|
&& let Ok(info) = ifd.image()
|
|
&& let [chunk] = info.chunks(data.len() as u64).as_slice()
|
|
&& let Some(s) = chunk_bytes(data, chunk)
|
|
&& is_jxl(s)
|
|
{
|
|
out.push(s);
|
|
}
|
|
}
|
|
|
|
/// The largest embedded preview, if any: a JPEG, or (DNG 1.7) a JPEG XL file — both decode with
|
|
/// `dac_codecs::decode`.
|
|
pub fn embedded_preview(bytes: &[u8]) -> Option<Vec<u8>> {
|
|
if bytes.starts_with(b"FUJIFILMCCD-RAW") {
|
|
let j = crate::vendor::raf::header(bytes).ok()?.jpeg?;
|
|
return is_dct_jpeg(j).then(|| trim_eoi(j).to_vec());
|
|
}
|
|
let format = crate::probe(bytes);
|
|
if format == Some(crate::RawFormat::Cr3) {
|
|
return cr3_preview(bytes).map(|j| trim_eoi(j).to_vec());
|
|
}
|
|
if matches!(format, Some(crate::RawFormat::Crw | crate::RawFormat::Mrw | crate::RawFormat::X3f)) {
|
|
return scan_for_jpeg(bytes);
|
|
}
|
|
let tiff = Tiff::parse(bytes).ok()?;
|
|
let mut found: Vec<&[u8]> = Vec::new();
|
|
for ifd in tiff.all_ifds() {
|
|
candidates(bytes, ifd, 0, &mut found);
|
|
}
|
|
// maker-note preview IFDs (e.g. Nikon PreviewIFD 0x0011 holds JPEGInterchangeFormat relative to the note base)
|
|
if let Some(exif) = tiff.exif()
|
|
&& let Some(e) = exif.get(t::MAKER_NOTE)
|
|
{
|
|
let make = tiff.find(t::MAKE).and_then(|e| e.value.as_str()).unwrap_or_default();
|
|
if let Some(mn) = makernote::parse_makernote(bytes, e.offset, e.count() as u64, tiff.order, &make) {
|
|
candidates(bytes, &mn.ifd, mn.base, &mut found);
|
|
if let Some(off) = mn.ifd.u64(0x0011)
|
|
&& let Ok((pifd, _)) = dac_tiff::parse_ifd_at(bytes, mn.base + off, mn.order, mn.base, false, &Default::default())
|
|
{
|
|
candidates(bytes, &pifd, mn.base, &mut found);
|
|
}
|
|
}
|
|
}
|
|
// Olympus: CameraSettings preview
|
|
if let Some(p) = crate::vendor::orf::preview(bytes) {
|
|
found.push(p);
|
|
}
|
|
let best = found
|
|
.into_iter()
|
|
.filter(|s| is_dct_jpeg(s) || is_jxl(s))
|
|
.max_by_key(|s| s.len())
|
|
.map(|s| if is_jxl(s) { s.to_vec() } else { trim_eoi(s).to_vec() });
|
|
// a TIFF raw we can't decode whose preview no tag points to (Leaf MOS, Epson ERF)
|
|
best.or_else(|| format.filter(|f| !f.is_supported()).and_then(|_| scan_for_jpeg(bytes)))
|
|
}
|
|
|
|
/// The end of the DCT JPEG whose SOI is at `soi` (exclusive index after its EOI) and its component count,
|
|
/// walking the marker segments and the entropy-coded data. `None` when it is not a complete, displayable
|
|
/// (baseline or progressive) JPEG, so a stray `D8 FF` in other data is rejected. `*reach` is left at
|
|
/// the furthest byte looked at (what the walk cost; see [`scan_for_jpeg`]).
|
|
fn jpeg_extent(b: &[u8], soi: usize, reach: &mut usize) -> Option<(usize, u8)> {
|
|
let mut i = soi + 2;
|
|
let r = walk_jpeg(b, &mut i);
|
|
*reach = i;
|
|
r
|
|
}
|
|
|
|
fn walk_jpeg(b: &[u8], i: &mut usize) -> Option<(usize, u8)> {
|
|
let mut components = None;
|
|
for _ in 0..4096 {
|
|
if *b.get(*i)? != 0xff {
|
|
return None;
|
|
}
|
|
while *b.get(*i)? == 0xff {
|
|
*i += 1;
|
|
}
|
|
let m = *b.get(*i)?;
|
|
*i += 1;
|
|
match m {
|
|
0xd9 => return components.map(|c| (*i, c)),
|
|
0x01 | 0xd0..=0xd8 => continue,
|
|
_ => {}
|
|
}
|
|
let len = usize::from(u16::from_be_bytes([*b.get(*i)?, *b.get(*i + 1)?]));
|
|
if len < 2 {
|
|
return None;
|
|
}
|
|
match m {
|
|
0xc0..=0xc2 => {
|
|
// precision, height, width, component count
|
|
let h = u16::from_be_bytes([*b.get(*i + 3)?, *b.get(*i + 4)?]);
|
|
let w = u16::from_be_bytes([*b.get(*i + 5)?, *b.get(*i + 6)?]);
|
|
if h == 0 || w == 0 || components.is_some() {
|
|
return None;
|
|
}
|
|
components = Some(*b.get(*i + 7)?);
|
|
}
|
|
0xc3 | 0xc5..=0xc7 | 0xc9..=0xcb | 0xcd..=0xcf => return None, // lossless, arithmetic, hierarchical
|
|
_ => {}
|
|
}
|
|
*i += len;
|
|
if m == 0xda {
|
|
// entropy-coded data up to the next marker that is not a stuffed 0xff or a restart
|
|
loop {
|
|
*i += b.get(*i..)?.iter().position(|&x| x == 0xff)?;
|
|
match *b.get(*i + 1)? {
|
|
0x00 | 0xd0..=0xd7 => *i += 2,
|
|
0xff => *i += 1,
|
|
_ => break,
|
|
}
|
|
}
|
|
}
|
|
}
|
|
None
|
|
}
|
|
|
|
/// Last resort for the containers whose structure is not walked (Canon CRW, Minolta MRW, Sigma X3F, TIFF raws
|
|
/// with private blocks such as Leaf MOS or Epson ERF): the largest complete colour DCT JPEG stored as a plain
|
|
/// byte run in the file. A one-component JPEG is skipped (a Canon PowerShot CRW stores its sensor mosaic as one).
|
|
///
|
|
/// Evidence: in the Minolta and Epson files the first byte of the stored preview is not `ff` (it is `00`, `02` or
|
|
/// `ee`) while the rest is a regular JPEG, so a run is found by its `d8 ff` and starts one byte earlier,
|
|
/// with that byte restored to `ff`.
|
|
///
|
|
/// A crafted file can hold millions of JPEG-like starts whose walks each run to its end: the walks
|
|
/// share a budget of eight times the file's size, so the scan stays linear (a real file's candidates
|
|
/// fail within a few bytes, or are the preview itself).
|
|
fn scan_for_jpeg(data: &[u8]) -> Option<Vec<u8>> {
|
|
let mut best: Option<(usize, usize)> = None;
|
|
let mut at = 1;
|
|
let mut budget = data.len().saturating_mul(8).max(1 << 20);
|
|
while let Some(off) = data.get(at..).and_then(|s| s.iter().position(|&b| b == 0xd8)) {
|
|
let d8 = at + off;
|
|
at = d8 + 1;
|
|
if data.get(d8 + 1) != Some(&0xff) || !matches!(data.get(d8 + 2), Some(0xc0..=0xc4 | 0xdb | 0xe0..=0xef | 0xfe)) {
|
|
continue;
|
|
}
|
|
let start = d8 - 1; // `at` starts at 1, so d8 >= 1
|
|
let mut reach = start;
|
|
let found = jpeg_extent(data, start, &mut reach);
|
|
budget = budget.saturating_sub(reach.saturating_sub(start));
|
|
if budget == 0 {
|
|
break;
|
|
}
|
|
if let Some((end, 3)) = found {
|
|
if best.is_none_or(|(s, e)| end - start > e - s) {
|
|
best = Some((start, end));
|
|
}
|
|
at = end;
|
|
}
|
|
}
|
|
let (start, end) = best?;
|
|
let mut jpeg = data.get(start..end)?.to_vec();
|
|
if let Some(first) = jpeg.first_mut() {
|
|
*first = 0xff;
|
|
}
|
|
Some(jpeg)
|
|
}
|
|
|
|
/// Canon CR3: the full-size JPEG track (see [`dac_meta::cr3`]), else the `PRVW` / `THMB` boxes.
|
|
fn cr3_preview(bytes: &[u8]) -> Option<&[u8]> {
|
|
let full =
|
|
dac_meta::cr3::parse_cr3(bytes).and_then(|c| c.tracks.iter().find(|t| t.kind == dac_meta::cr3::Cr3TrackKind::Jpeg).and_then(|t| t.data));
|
|
if let Some(j) = full.and_then(|(at, len)| bytes.get(at..at.checked_add(len)?)).filter(|j| is_dct_jpeg(j)) {
|
|
return Some(j);
|
|
}
|
|
cr3_preview_boxes(bytes)
|
|
}
|
|
|
|
/// Canon CR3 (ISO base media file): the `PRVW` box (Laurent Clévy's CR3 notes; layout confirmed on a CC0
|
|
/// sample) is `u32 size, "PRVW", u32 0, u16 ?, u16 width, u16 height, u16 ?, u32 jpeg length, JPEG`; the smaller
|
|
/// `THMB` box has the same shape. Returns the larger valid one.
|
|
fn cr3_preview_boxes(bytes: &[u8]) -> Option<&[u8]> {
|
|
let mut best: Option<&[u8]> = None;
|
|
for tag in [b"PRVW", b"THMB"] {
|
|
let mut from = 0;
|
|
while let Some(i) = bytes.get(from..).and_then(|s| s.windows(4).position(|w| w == tag)).map(|p| p + from) {
|
|
from = i + 4;
|
|
let Some(start) = i.checked_sub(4) else { continue };
|
|
let be32 = |at: usize| bytes.get(at..at + 4).map(|s| u32::from_be_bytes([s[0], s[1], s[2], s[3]]) as usize);
|
|
let (Some(size), Some(len)) = (be32(start), be32(start + 20)) else { continue };
|
|
let j = start + 24;
|
|
if len < 4 || j + len > start + size.max(24) || j + len > bytes.len() {
|
|
continue;
|
|
}
|
|
let jpeg = &bytes[j..j + len];
|
|
if is_dct_jpeg(jpeg) {
|
|
if best.is_none_or(|b| b.len() < jpeg.len()) {
|
|
best = Some(jpeg);
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
best
|
|
}
|
|
|
|
/// Trim trailing garbage after the last EOI when a stored length over-reports.
|
|
fn trim_eoi(s: &[u8]) -> &[u8] {
|
|
let end = s.windows(2).rposition(|w| w == [0xff, 0xd9]).map(|p| p + 2).unwrap_or(s.len());
|
|
&s[..end]
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
use dac_tiff::{IfdBuilder, ImageData, TiffWriter, Value};
|
|
|
|
fn fake_jpeg(n: usize) -> Vec<u8> {
|
|
let mut j = vec![0xff, 0xd8, 0xff, 0xc0, 0x00, 0x0b, 8, 0, 1, 0, 1, 1, 1, 0x11, 0];
|
|
j.extend(std::iter::repeat_n(0x55u8, n));
|
|
j.extend_from_slice(&[0xff, 0xd9]);
|
|
j
|
|
}
|
|
|
|
#[test]
|
|
fn picks_largest_dct_jpeg() {
|
|
let small = fake_jpeg(10);
|
|
let big = fake_jpeg(500);
|
|
let lossless = crate::ljpeg::encode(&[1u16; 64], 8, 8, 1, 12, 1, 0);
|
|
let mut ifd0 = IfdBuilder::new();
|
|
ifd0.set(t::COMPRESSION, Value::Short(vec![6]));
|
|
ifd0.set(t::IMAGE_WIDTH, Value::Long(vec![1]));
|
|
ifd0.set(t::IMAGE_LENGTH, Value::Long(vec![1]));
|
|
ifd0.set_image(ImageData::Strips { rows_per_strip: 1, strips: vec![small.clone()] });
|
|
let mut raw = IfdBuilder::new();
|
|
raw.set(t::COMPRESSION, Value::Short(vec![7]));
|
|
raw.set(t::IMAGE_WIDTH, Value::Long(vec![8]));
|
|
raw.set(t::IMAGE_LENGTH, Value::Long(vec![8]));
|
|
raw.set_image(ImageData::Strips { rows_per_strip: 8, strips: vec![lossless] });
|
|
ifd0.add_sub_ifd(raw);
|
|
let mut sub = IfdBuilder::new();
|
|
sub.set(t::COMPRESSION, Value::Short(vec![7]));
|
|
sub.set(t::IMAGE_WIDTH, Value::Long(vec![2]));
|
|
sub.set(t::IMAGE_LENGTH, Value::Long(vec![2]));
|
|
sub.set(t::NEW_SUBFILE_TYPE, Value::Long(vec![1]));
|
|
sub.set_image(ImageData::Strips { rows_per_strip: 2, strips: vec![big.clone()] });
|
|
ifd0.add_sub_ifd(sub);
|
|
let bytes = TiffWriter::default().write(&[ifd0]).unwrap();
|
|
assert_eq!(embedded_preview(&bytes).unwrap(), big);
|
|
assert!(embedded_preview(b"nope").is_none());
|
|
// CR3: a PRVW box after the ftyp
|
|
let mut cr3 = b"\0\0\0\x18ftypcrx \0\0\0\x01crx isom".to_vec();
|
|
let j = fake_jpeg(300);
|
|
cr3.extend_from_slice(&((24 + j.len()) as u32).to_be_bytes());
|
|
cr3.extend_from_slice(b"PRVW\0\0\0\0\0\x01\x06\x54\x04\x38\0\x01");
|
|
cr3.extend_from_slice(&(j.len() as u32).to_be_bytes());
|
|
cr3.extend_from_slice(&j);
|
|
assert_eq!(embedded_preview(&cr3).unwrap(), j);
|
|
for n in 0..cr3.len() {
|
|
let _ = embedded_preview(&cr3[..n]);
|
|
}
|
|
}
|
|
|
|
/// CR3 with a full-size JPEG track: that JPEG wins over the smaller `PRVW` box.
|
|
#[test]
|
|
fn cr3_prefers_the_full_size_jpeg_track() {
|
|
let bx = |kind: &[u8; 4], body: &[u8]| -> Vec<u8> { [&((body.len() + 8) as u32).to_be_bytes()[..], kind, body].concat() };
|
|
let full = |kind: &[u8; 4], body: &[u8]| bx(kind, &[&[0u8; 4][..], body].concat());
|
|
let (small, big) = (fake_jpeg(300), fake_jpeg(3000));
|
|
let mut file = bx(b"ftyp", b"crx \0\0\0\x01crx isom");
|
|
let mut prvw = b"\0\0\0\0\0\x01\x06\x54\x04\x38\0\x01".to_vec();
|
|
prvw.extend_from_slice(&(small.len() as u32).to_be_bytes());
|
|
prvw.extend_from_slice(&small);
|
|
file.extend(bx(b"PRVW", &prvw));
|
|
// CRAW sample entry: 82 bytes, then a JPEG child box; one sample at `at`
|
|
let mut craw = vec![0u8; 82];
|
|
craw.extend(bx(b"JPEG", &[0; 4]));
|
|
let at = 2048u64;
|
|
let stsd = full(b"stsd", &[&1u32.to_be_bytes()[..], &bx(b"CRAW", &craw)].concat());
|
|
let stsz = full(b"stsz", &[0u32.to_be_bytes(), 1u32.to_be_bytes(), (big.len() as u32).to_be_bytes()].concat());
|
|
let co64 = full(b"co64", &[&1u32.to_be_bytes()[..], &at.to_be_bytes()].concat());
|
|
let trak = bx(b"trak", &bx(b"mdia", &bx(b"minf", &bx(b"stbl", &[stsd, stsz, co64].concat()))));
|
|
file.extend(bx(b"moov", &trak));
|
|
file.resize(at as usize, 0);
|
|
file.extend_from_slice(&big);
|
|
assert_eq!(embedded_preview(&file).unwrap(), big);
|
|
// a track pointing past the end falls back to PRVW
|
|
file.truncate(at as usize + 100);
|
|
assert_eq!(embedded_preview(&file).unwrap(), small);
|
|
}
|
|
|
|
/// A structurally complete DCT JPEG (no real image data): `nc` components, `n` entropy bytes.
|
|
fn scan_jpeg(nc: u8, n: usize) -> Vec<u8> {
|
|
let mut j = vec![0xff, 0xd8, 0xff, 0xdb, 0x00, 0x43, 0x00];
|
|
j.extend(std::iter::repeat_n(8u8, 64));
|
|
j.extend_from_slice(&[0xff, 0xc0, 0x00, 8 + 3 * nc, 8, 0, 16, 0, 24, nc]);
|
|
for c in 0..nc {
|
|
j.extend_from_slice(&[c + 1, 0x11, 0]);
|
|
}
|
|
j.extend_from_slice(&[0xff, 0xda, 0x00, 6 + 2 * nc, nc]);
|
|
for c in 0..nc {
|
|
j.extend_from_slice(&[c + 1, 0]);
|
|
}
|
|
j.extend_from_slice(&[0, 63, 0]);
|
|
j.extend(std::iter::repeat_n(0x55u8, n));
|
|
j.extend_from_slice(&[0xff, 0x00, 0x12, 0xff, 0xd0, 0x34, 0xff, 0xd9]);
|
|
j
|
|
}
|
|
|
|
/// A crafted container full of JPEG-like starts (each walk running on through the ones after it)
|
|
/// is scanned in linear time: the walks share a budget (without it this 40 MB file takes about a minute).
|
|
#[test]
|
|
fn a_scan_through_many_fake_jpegs_stays_linear() {
|
|
let mut unit = vec![0u8, 0xd8, 0xff, 0xdb, 0x00, 0x02, 0xff, 0xda, 0x00, 0x02];
|
|
unit.extend(std::iter::repeat_n(0x55u8, 190));
|
|
let mut f = b"\0MRM\0\x01\0\0".to_vec();
|
|
for _ in 0..200_000 {
|
|
f.extend_from_slice(&unit);
|
|
}
|
|
let t = std::time::Instant::now();
|
|
assert_eq!(scan_for_jpeg(&f), None);
|
|
assert!(t.elapsed() < std::time::Duration::from_secs(10), "{:?}", t.elapsed());
|
|
}
|
|
|
|
/// Containers whose structure we do not walk give up their largest colour JPEG, found by scanning.
|
|
#[test]
|
|
fn scanned_containers_give_the_largest_colour_jpeg() {
|
|
let (small, big, mosaic) = (scan_jpeg(3, 100), scan_jpeg(3, 900), scan_jpeg(1, 5000));
|
|
let heads: [&[u8]; 3] = [b"II\x1a\0\0\0HEAPCCDR", b"\0MRM\0\x01\0\0", b"FOVb\x02\0\x02\0"];
|
|
for head in heads {
|
|
let mut f = head.to_vec();
|
|
for part in [&small, &mosaic, &big] {
|
|
f.extend_from_slice(&[0xff, 0xd8, 0xff, 0x00, 0x00]); // a stray SOI-like run: not a JPEG
|
|
f.extend_from_slice(part);
|
|
f.extend_from_slice(&[0u8; 7]);
|
|
}
|
|
assert!(crate::probe(&f).is_some_and(|p| !p.is_supported()), "{head:?}");
|
|
assert_eq!(embedded_preview(&f).as_deref(), Some(&big[..]), "{head:?}");
|
|
for n in (0..f.len()).step_by(11) {
|
|
let _ = embedded_preview(&f[..n]);
|
|
}
|
|
}
|
|
// a preview whose first byte was overwritten (Minolta and Epson files store 00, 02 or ee there) is restored
|
|
let mut f = b"\0MRM\0\x01\0\0".to_vec();
|
|
f.push(0x02);
|
|
f.extend_from_slice(&big[1..]);
|
|
assert_eq!(embedded_preview(&f).as_deref(), Some(&big[..]));
|
|
// only a one-component JPEG, or none: nothing
|
|
let mut f = b"FOVb\x02\0\x02\0".to_vec();
|
|
f.extend_from_slice(&mosaic);
|
|
assert_eq!(embedded_preview(&f), None);
|
|
}
|
|
}
|