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wml2 is a callback-based image I/O library for Rust.

• decodes and encodes images in memory
• works with the built-in RGBA ImageBuffer or custom callbacks
• supports still images and selected animation / multi-page formats
• includes native file helpers on non-WASM targets

See wml2-test/examples.

$ cargo run -p wml2-test --example to_bmp --release -- <inputfile> <output_dir>

$ cargo run -p wml2-test --example metadata --release -- <inputfile>

$ cargo run -p wml2-test --example converter -- <inputfiles...> -o <output_dir> [-f gif|png|jpeg|bmp|tiff|webp] [-q <quality>] [-z <0-9>] [-c <none|lzw|lzw_msb|lzw_lsb|jpeg|lossy|lossless>] [--exif copy] [--split]

• default: legacy decoders are enabled
• noretoro: disables MAKI, PI, PIC, VSP/DAT, and PCD

[dependencies] wml2 = "0.0.18"

[dependencies] wml2 = { version = "0.0.18", features = ["noretoro"] }

draw::image_to() encodes an ImageBuffer directly into a Vec<u8>.

draw::convert() chooses the encoder from the output extension: .gif, .png, .apng, .jpg, .jpeg, .bmp, .tif, .tiff, .webp.

Supported option keys in EncodeOptions::options / draw::convert(..., options):

• JPEG: quality
• TIFF: compression = none|lzw|lzw_msb|lzw_lsb|jpeg
• TIFF with compression=jpeg: quality
• WebP: optimize (0..=9)
• WebP lossy: quality
• PNG/JPEG/TIFF/WebP: exif
  • raw EXIF bytes via DataMap::Raw
  • TIFF-style EXIF via DataMap::Exif
  • DataMap::Ascii("copy".to_string()) to preserve decoded EXIF during convert()

wml2-test/examples/converter options:

• -q: JPEG quality, WebP lossy quality, or TIFF JPEG quality
• -z: WebP optimize level
• -c: TIFF compression or WebP lossy|lossless
• --exif copy: copy source EXIF to PNG/JPEG/TIFF/WebP output
• --split: split animation / multi-frame output for GIF/PNG/TIFF/WebP

Encode supports:

• no compression
• LZW
• JPEG (new-style TIFF JPEG, RGB only)

Decode supports:

• no compression
• LZW
• PackBits
• JPEG (new-style TIFF JPEG)
• Adobe Deflate
• CCITT Huffman RLE
• CCITT Group 3 Fax
• CCITT Group 4 Fax

For simple in-memory decoding, use draw::image_load(). For native file I/O, use draw::image_from_file().

use std::error::Error; use wml2::draw::{PickCallback, image_from_file}; fn main() -> Result<(), Box<dyn Error>> { let mut image = image_from_file("foo.webp".to_string())?; println!("{}x{}", image.width, image.height); if let Some(metadata) = image.metadata()? { if let Some(format) = metadata.get("Format") { println!("format: {:?}", format); } } Ok(()) }

Use draw::image_loader() or draw::image_reader() when you want decoders to write into a custom DrawCallback.

ImageBuffer implements DrawCallback and receives:

• init: initialize the canvas
• draw: write RGBA pixels into a rectangle
• next: receive NextOptions for animation or multi-image transitions
• terminate: finalize decoding
• verbose: decoder-specific debug output
• set_metadata: decoded metadata

Use draw::image_to() for ImageBuffer, or draw::image_encoder() / draw::image_writer() when you want to encode a custom PickCallback.

use std::collections::HashMap; use std::error::Error; use wml2::draw::{ImageBuffer, image_to}; use wml2::metadata::DataMap; use wml2::util::ImageFormat; fn main() -> Result<(), Box<dyn Error>> { let mut image = ImageBuffer::from_buffer(1, 1, vec![255, 0, 0, 255]); let mut options = HashMap::new(); options.insert("quality".to_string(), DataMap::UInt(90)); let jpeg = image_to(&mut image, ImageFormat::Jpeg, Some(options))?; assert!(jpeg.starts_with(&[0xff, 0xd8])); Ok(()) }

ImageBuffer implements PickCallback and provides:

• encode_start
• encode_pick
• encode_end
• metadata

Metadata is stored as HashMap<String, DataMap>.

use std::error::Error; use wml2::draw::{PickCallback, image_from_file}; use wml2::metadata::DataMap; fn main() -> Result<(), Box<dyn Error>> { let mut image = image_from_file("foo.jpg".to_string())?; let metadata = image.metadata()?.unwrap_or_default(); if let Some(DataMap::ICCProfile(profile)) = metadata.get("ICC Profile") { println!("ICC profile: {} bytes", profile.len()); } Ok(()) }

• integration tests use generic names such as sample.mki, sample.pi, sample.pic, sample.dat
• original sample filenames are intentionally not referenced in public test code
• optional external sample paths can be configured in wml2/tests/test_samples.txt
• wml2/tests/test_samples.txt is ignored by git; use wml2/tests/test_samples.example.txt as a template

• 0x01: basic header
• 0x02: Huffman table
• 0x04: extracted Huffman table
• 0x08: quantization table
• 0x10: EXIF
• 0x20: ICC profile header
• 0x40: ICC profile detail
• 0x60: ICC profile all

• 0.0.1: baseline JPEG
• 0.0.2: BMP OS/2 and Windows RGB/RLE4/RLE8/bit fields, baseline JPEG
• 0.0.3: GIF decoder
• 0.0.4: error message updates
• 0.0.5: reader and error propagation changes
• 0.0.6: RST marker read bug fix
• 0.0.7: PNG decoder
• 0.0.8: pipelined JPEG, BMP saver, animation GIF work
• 0.0.9: PNG saver
• 0.0.10: progressive JPEG fix
• 0.0.11: TIFF Group 3/4 Fax and multipage TIFF decode improvements
• 0.0.12: encode option changes
• 0.0.13: MAG decoder
• 0.0.14: MAKI/PI/PIC/VSP(DAT)/PCD decoders and noretoro
• 0.0.15: baseline JPEG encoder
• 0.0.16: pure Rust WebP decoder and APNG encoder
• 0.0.17: pure Rust WebP encoder and animated WebP encode
• 0.0.18: GIF encoder, TIFF encoder, EXIF writer

MIT License (C) 2022-2026

MITH@mmk https://mith-mmk.github.io/