commit 4947f799888e707ec5c1272fd2c1f35865b7906b
parent 37974df26522bda17c1d176a626a6861dca813aa
Author: mauricefisher64 <92736594+mauricefisher64@users.noreply.github.com>
Date: Thu, 25 Aug 2022 18:16:20 -0400
Fast XMP extraction from PNG (#117)
* Don't use PNG lib since it decode image. Use our chunk parsing to handle the iTXt chunk.
* Disable compressed iTXt reading since XMP is always uncompressed.
* Bump required rust version
* Fix build issue caused by removed code
Diffstat:
3 files changed, 122 insertions(+), 7 deletions(-)
diff --git a/sdk/Cargo.toml b/sdk/Cargo.toml
@@ -93,6 +93,7 @@ instant = "0.1.0"
openssl = { version = "0.10.31", features = ["vendored"], optional = true }
xmp_toolkit = { version = "0.5.1", optional = true }
+
[target.'cfg(target_arch = "wasm32")'.dependencies]
console_log = { version = "0.2", features = ["color"] }
getrandom = { version = "0.2.7", features = ["js"] }
diff --git a/sdk/src/asset_handlers/png_io.rs b/sdk/src/asset_handlers/png_io.rs
@@ -148,6 +148,28 @@ fn add_required_chunks(asset_path: &std::path::Path) -> Result<()> {
}
}
}
+
+fn read_string(asset_reader: &mut dyn CAIRead, max_read: u32) -> Result<String> {
+ let mut bytes_read: u32 = 0;
+ let mut s: Vec<u8> = Vec::with_capacity(80);
+
+ loop {
+ let c = asset_reader.read_u8()?;
+ if c == 0 {
+ break;
+ }
+
+ s.push(c);
+
+ bytes_read += 1;
+
+ if bytes_read == max_read {
+ break;
+ }
+ }
+
+ Ok(String::from_utf8_lossy(&s).to_string())
+}
pub struct PngIO {}
impl CAILoader for PngIO {
@@ -158,15 +180,93 @@ impl CAILoader for PngIO {
// Get XMP block
fn read_xmp(&self, asset_reader: &mut dyn CAIRead) -> Option<String> {
- let chunks = png_pong::Decoder::new(asset_reader).ok()?.into_chunks();
- for chunk_r in chunks.flatten() {
- if let png_pong::chunk::Chunk::InternationalText(c) = chunk_r {
- if c.key == XMP_KEY {
- return Some(c.val);
+ const ITXT_CHUNK: [u8; 4] = *b"iTXt";
+
+ let ps = get_png_chunk_positions(asset_reader).ok()?;
+ let mut xmp_str: Option<String> = None;
+
+ ps.into_iter().find(|pcp| {
+ if pcp.name == ITXT_CHUNK {
+ // seek to start of chunk
+ if asset_reader.seek(SeekFrom::Start(pcp.start + 8)).is_err() {
+ // move +8 to get past header
+ return false;
+ }
+
+ // parse the iTxt block
+ if let Ok(key) = read_string(asset_reader, pcp.length) {
+ if key.is_empty() || key.len() > 79 {
+ return false;
+ }
+
+ // is this an XMP key
+ if key != XMP_KEY {
+ return false;
+ }
+
+ // parse rest of iTxt to get the xmp value
+ let compressed = match asset_reader.read_u8() {
+ Ok(c) => c != 0,
+ Err(_) => return false,
+ };
+
+ let _compression_method = match asset_reader.read_u8() {
+ Ok(c) => c != 0,
+ Err(_) => return false,
+ };
+
+ let _langtag = match read_string(asset_reader, pcp.length) {
+ Ok(s) => s,
+ Err(_) => return false,
+ };
+
+ let _transkey = match read_string(asset_reader, pcp.length) {
+ Ok(s) => s,
+ Err(_) => return false,
+ };
+
+ // read iTxt data
+ let mut data = vec![
+ 0u8;
+ pcp.length as usize
+ - (key.len() + _langtag.len() + _transkey.len() + 5)
+ as usize
+ ]; // data len - size of key - size of land - size of transkey - 3 "0" string terminators - compressed u8 - compression method u8
+ if asset_reader.read_exact(&mut data).is_err() {
+ return false;
+ }
+
+ // convert to string, decompress if needed
+ let val = if compressed {
+ /* should not be needed for current XMP
+ use flate2::read::GzDecoder;
+
+ let cursor = Cursor::new(data);
+
+ let mut d = GzDecoder::new(cursor);
+ let mut s = String::new();
+ if d.read_to_string(&mut s).is_err() {
+ return false;
+ }
+ s
+ */
+ return false;
+ } else {
+ String::from_utf8_lossy(&data).to_string()
+ };
+
+ xmp_str = Some(val);
+
+ true
+ } else {
+ false
}
+ } else {
+ false
}
- }
- None
+ });
+
+ xmp_str
}
}
@@ -296,6 +396,20 @@ pub mod tests {
use super::*;
#[test]
+ fn test_png_xmp() {
+ let ap = crate::utils::test::fixture_path("libpng-test_with_url.png");
+
+ let png_io = PngIO {};
+ let xmp = png_io
+ .read_xmp(&mut std::fs::File::open(&ap).unwrap())
+ .unwrap();
+
+ // make sure we can parse it
+ let provenance = crate::utils::xmp_inmemory_utils::extract_provenance(&xmp).unwrap();
+
+ assert!(provenance.contains("libpng-test"));
+ }
+ #[test]
fn test_png_parse() {
let ap = crate::utils::test::fixture_path("libpng-test.png");
diff --git a/sdk/tests/fixtures/libpng-test_with_url.png b/sdk/tests/fixtures/libpng-test_with_url.png
Binary files differ.
