Little CMS wrapper for Rust

Convert and apply color profiles with a safe abstraction layer for the LCMS library.

See API reference for Rust functions and the LCMS2 documentation HTML/PDF for more background information about the functions.

use lcms2::*;

fn example() -> Result<(), std::io::Error> {
    let icc_file = include_bytes!("custom_profile.icc"); // You can use Profile::new_file("path"), too
    let custom_profile = Profile::new_icc(icc_file)?;

    let srgb_profile = Profile::new_srgb();

    let t = Transform::new(&custom_profile, PixelFormat::RGB_8, &srgb_profile, PixelFormat::RGB_8, Intent::Perceptual);

    // Pixel struct must have layout compatible with PixelFormat specified in new()
    let source_pixels: &[rgb::RGB<u8>] = …;
    t.transform_pixels(source_pixels, destination_pixels);

    // If input and output pixel formats are the same, you can overwrite them instead of copying
    t.transform_in_place(source_and_dest_pixels);

    Ok(())
}

To apply an ICC profile from a JPEG:

if b"ICC_PROFILE\0" == &app2_marker_data[0..12] {
   let icc = &app2_marker_data[14..]; // Lazy assumption that the profile is smaller than 64KB
   let profile = Profile::new_icc(icc)?;
   let t = Transform::new(&profile, PixelFormat::RGB_8,
       &Profile::new_srgb(), PixelFormat::RGB_8, Intent::Perceptual);
   t.transform_in_place(&mut rgb);
}

There's more in the examples directory.

This crate requires Rust 1.33 or later. It's up to date with LCMS 2.9, and should work with 2.6 to 2.9.

Threads

In LCMS all functions are in 2 flavors: global and *THR() functions. In this crate this is represented by having functions with GlobalContext and ThreadContext. Create profiles, transforms, etc. using *_context() constructors to give them their private coontext, which makes them sendable between threads (i.e. they're Send).

By default Transform does not implement Sync, because LCMS2 has a thread-unsafe cache in the transform. You can set Flags::NO_CACHE to make it safe (this is checked at compile time).