pngmeta

Low-level PNG tEXt chunk reader/writer. No image decoding — operates directly on binary PNG structure using only std + memchr.

Features

• Read — extract all tEXt chunks as BTreeMap<String, String>
• Scan — streaming predicate search with early exit (no allocation per chunk)
• Contains — SIMD-accelerated (memchr::memmem) binary pattern search
• Write — insert tEXt chunks before IEND with correct CRC-32

Usage

use std::path::Path;
use pngmeta::{read_text_chunks, contains_in_text_chunks, write_text_chunk};

// Read all tEXt chunks
let chunks = read_text_chunks(Path::new("image.png"))?;
for (key, value) in &chunks {
    println!("{key}: {value}");
}

// Fast binary search (no UTF-8 decoding)
if contains_in_text_chunks(Path::new("image.png"), b"seed")? {
    println!("found");
}

// Write a tEXt chunk
write_text_chunk(Path::new("image.png"), "prompt", "a cat")?;

Feature Flags

License

MIT