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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
use crate::{error::Result, util::NewWithCapacity};
use super::{ICC_HEADER_SIZE, IccStream};
fn predict_header(idx: usize, output_size: u32, header: &[u8]) -> u8 {
match idx {
0..=3 => output_size.to_be_bytes()[idx],
8 => 4,
12..=23 => b"mntrRGB XYZ "[idx - 12],
36..=39 => b"acsp"[idx - 36],
// APPL
41 | 42 if header[40] == b'A' => b'P',
43 if header[40] == b'A' => b'L',
// MSFT
41 if header[40] == b'M' => b'S',
42 if header[40] == b'M' => b'F',
43 if header[40] == b'M' => b'T',
// SGI_
42 if header[40] == b'S' && header[41] == b'G' => b'I',
43 if header[40] == b'S' && header[41] == b'G' => b' ',
// SUNW
42 if header[40] == b'S' && header[41] == b'U' => b'N',
43 if header[40] == b'S' && header[41] == b'U' => b'W',
70 => 246,
71 => 214,
73 => 1,
78 => 211,
79 => 45,
80..=83 => header[4 + idx - 80],
_ => 0,
}
}
pub(super) fn read_header(data_stream: &mut IccStream, output_size: u64) -> Result<Vec<u8>> {
let header_size = output_size.min(ICC_HEADER_SIZE);
let header_data = data_stream.read_to_vec_exact(header_size as usize)?;
let mut profile = Vec::new_with_capacity(output_size as usize)?;
for (idx, &e) in header_data.iter().enumerate() {
let p = predict_header(idx, output_size as u32, &header_data);
profile.push(p.wrapping_add(e));
}
Ok(profile)
}