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Recompress iCCP

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This commit is contained in:
Andrew 2023-05-16 21:34:01 +12:00
parent acfc63399d
commit 7372f740b5
2 changed files with 104 additions and 64 deletions
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73
src/headers.rs
View file

@ -1,9 +1,12 @@
use crate::colors::{BitDepth, ColorType};
use crate::deflate::crc32;
use crate::deflate::{crc32, inflate};
use crate::error::PngError;
use crate::interlace::Interlacing;
use crate::AtomicMin;
use crate::Deflaters;
use crate::PngResult;
use indexmap::IndexSet;
use log::warn;
use rgb::{RGB16, RGBA8};
#[derive(Debug, Clone)]
@ -214,3 +217,71 @@ fn palette_to_rgba(
fn read_be_u32(bytes: &[u8]) -> u32 {
u32::from_be_bytes(bytes.try_into().unwrap())
}
/// Extract and decompress the ICC profile from an iCCP chunk
pub fn extract_icc(iccp: &Chunk) -> Option<Vec<u8>> {
// Skip (useless) profile name
let mut data = iccp.data.as_slice();
loop {
let (&n, rest) = data.split_first()?;
data = rest;
if n == 0 {
break;
}
}
let (&compression_method, compressed_data) = data.split_first()?;
if compression_method != 0 {
return None; // The profile is supposed to be compressed (method 0)
}
// The decompressed size is unknown so we have to guess the required buffer size
let max_size = compressed_data.len() * 2 + 1000;
match inflate(compressed_data, max_size) {
Ok(icc) => Some(icc),
Err(e) => {
// Log the error so we can know if the buffer size needs to be adjusted
warn!("Failed to decompress icc: {}", e);
None
}
}
}
/// Construct an iCCP chunk by compressing the ICC profile
pub fn construct_iccp(icc: &[u8], deflater: Deflaters) -> PngResult<Chunk> {
let mut compressed = deflater.deflate(icc, &AtomicMin::new(None))?;
let mut data = Vec::with_capacity(compressed.len() + 5);
data.extend(b"icc"); // Profile name - generally unused, can be anything
data.extend([0, 0]); // Null separator, zlib compression method
data.append(&mut compressed);
Ok(Chunk {
name: *b"iCCP",
data,
})
}
/// If the profile is sRGB, extracts the rendering intent value from it
pub fn srgb_rendering_intent(icc_data: &[u8]) -> Option<u8> {
let rendering_intent = *icc_data.get(67)?;
// The known profiles are the same as in libpng's `png_sRGB_checks`.
// The Profile ID header of ICC has a fixed layout,
// and is supposed to contain MD5 of profile data at this offset
match icc_data.get(84..100)? {
b"\x29\xf8\x3d\xde\xaf\xf2\x55\xae\x78\x42\xfa\xe4\xca\x83\x39\x0d"
| b"\xc9\x5b\xd6\x37\xe9\x5d\x8a\x3b\x0d\xf3\x8f\x99\xc1\x32\x03\x89"
| b"\xfc\x66\x33\x78\x37\xe2\x88\x6b\xfd\x72\xe9\x83\x82\x28\xf1\xb8"
| b"\x34\x56\x2a\xbf\x99\x4c\xcd\x06\x6d\x2c\x57\x21\xd0\xd6\x8c\x5d" => {
Some(rendering_intent)
}
b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" => {
// Known-bad profiles are identified by their CRC
match (crc32(icc_data), icc_data.len()) {
(0x5d51_29ce, 3024) | (0x182e_a552, 3144) | (0xf29e_526d, 3144) => {
Some(rendering_intent)
}
_ => None,
}
}
_ => None,
}
}

95
src/lib.rs
View file

@ -25,9 +25,8 @@ extern crate rayon;
mod rayon;
use crate::atomicmin::AtomicMin;
use crate::deflate::{crc32, inflate};
use crate::evaluate::Evaluator;
use crate::headers::{Chunk, IhdrData};
use crate::headers::*;
use crate::png::PngData;
use crate::png::PngImage;
use crate::reduction::*;
@ -374,13 +373,10 @@ impl RawImage {
/// Add an ICC profile for the image
pub fn add_icc_profile(&mut self, data: &[u8]) {
// Compress with default compression level
if let Ok(mut compressed) = deflate::deflate(data, 11, &AtomicMin::new(None)) {
let mut iccp = Vec::with_capacity(compressed.len() + 13);
iccp.extend(b"icc"); // Profile name - generally unused, can be anything
iccp.extend([0, 0]); // Null separator, zlib compression method
iccp.append(&mut compressed);
self.add_png_chunk(*b"iCCP", iccp);
// Compress with fastest compression level - will be recompressed during optimization
let deflater = Deflaters::Libdeflater { compression: 1 };
if let Ok(iccp) = construct_iccp(data, deflater) {
self.aux_chunks.push(iccp);
}
}
@ -844,21 +840,38 @@ fn report_format(prefix: &str, png: &PngImage) {
/// Perform cleanup of certain chunks from the `PngData` object, after optimization has been completed
fn postprocess_chunks(png: &mut PngData, opts: &Options, orig_ihdr: &IhdrData) {
// See if we can replace an iCCP chunk with an sRGB chunk
if opts.strip != StripChunks::None && opts.strip.keep(b"sRGB") {
if let Some(iccp_idx) = png.aux_chunks.iter().position(|c| &c.name == b"iCCP") {
if png.aux_chunks.iter().any(|c| &c.name == b"sRGB") {
// Files aren't supposed to have both chunks, so we chose to honor sRGB
trace!("Removing iCCP chunk due to conflict with sRGB chunk");
png.aux_chunks.remove(iccp_idx);
} else if let Some(intent) = srgb_rendering_intent(&png.aux_chunks[iccp_idx].data) {
// sRGB-like profile can be safely replaced with
// an sRGB chunk with the same rendering intent
if let Some(iccp_idx) = png.aux_chunks.iter().position(|c| &c.name == b"iCCP") {
// See if we can replace an iCCP chunk with an sRGB chunk
let may_replace_iccp = opts.strip != StripChunks::None && opts.strip.keep(b"sRGB");
if may_replace_iccp && png.aux_chunks.iter().any(|c| &c.name == b"sRGB") {
// Files aren't supposed to have both chunks, so we chose to honor sRGB
trace!("Removing iCCP chunk due to conflict with sRGB chunk");
png.aux_chunks.remove(iccp_idx);
} else if let Some(icc) = extract_icc(&png.aux_chunks[iccp_idx]) {
let intent = if may_replace_iccp {
srgb_rendering_intent(&icc)
} else {
None
};
// sRGB-like profile can be replaced with an sRGB chunk with the same rendering intent
// Otherwise try recompressing the profile
if let Some(intent) = intent {
trace!("Replacing iCCP chunk with equivalent sRGB chunk");
png.aux_chunks[iccp_idx] = Chunk {
name: *b"sRGB",
data: vec![intent],
};
} else if let Ok(iccp) = construct_iccp(&icc, opts.deflate) {
let cur_len = png.aux_chunks[iccp_idx].data.len();
let new_len = iccp.data.len();
if new_len < cur_len {
debug!(
"Recompressed iCCP chunk: {} ({} bytes decrease)",
new_len,
cur_len - new_len
);
png.aux_chunks[iccp_idx] = iccp;
}
}
}
}
@ -880,50 +893,6 @@ fn postprocess_chunks(png: &mut PngData, opts: &Options, orig_ihdr: &IhdrData) {
}
}
/// If the profile is sRGB, extracts the rendering intent value from it
fn srgb_rendering_intent(mut iccp: &[u8]) -> Option<u8> {
// Skip (useless) profile name
loop {
let (&n, rest) = iccp.split_first()?;
iccp = rest;
if n == 0 {
break;
}
}
let (&compression_method, compressed_data) = iccp.split_first()?;
if compression_method != 0 {
return None; // The profile is supposed to be compressed (method 0)
}
// The decompressed size is unknown so we have to guess the required buffer size
let max_size = (compressed_data.len() * 2).max(1000);
let icc_data = inflate(compressed_data, max_size).ok()?;
let rendering_intent = *icc_data.get(67)?;
// The known profiles are the same as in libpng's `png_sRGB_checks`.
// The Profile ID header of ICC has a fixed layout,
// and is supposed to contain MD5 of profile data at this offset
match icc_data.get(84..100)? {
b"\x29\xf8\x3d\xde\xaf\xf2\x55\xae\x78\x42\xfa\xe4\xca\x83\x39\x0d"
| b"\xc9\x5b\xd6\x37\xe9\x5d\x8a\x3b\x0d\xf3\x8f\x99\xc1\x32\x03\x89"
| b"\xfc\x66\x33\x78\x37\xe2\x88\x6b\xfd\x72\xe9\x83\x82\x28\xf1\xb8"
| b"\x34\x56\x2a\xbf\x99\x4c\xcd\x06\x6d\x2c\x57\x21\xd0\xd6\x8c\x5d" => {
Some(rendering_intent)
}
b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" => {
// Known-bad profiles are identified by their CRC
match (crc32(&icc_data), icc_data.len()) {
(0x5d51_29ce, 3024) | (0x182e_a552, 3144) | (0xf29e_526d, 3144) => {
Some(rendering_intent)
}
_ => None,
}
}
_ => None,
}
}
/// Check if an image was already optimized prior to oxipng's operations
fn is_fully_optimized(original_size: usize, optimized_size: usize, opts: &Options) -> bool {
original_size <= optimized_size && !opts.force