appthere-color

Document-aware color management for Rust — pure Rust ICC transforms, CMYK, soft proofing, and print-ready color policies.

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appthere-color fills a gap in the Rust ecosystem: a color model built for document authoring and print workflows, rather than pixel rendering. It provides named color values, CMYK ink representation, ICC profile transforms via a pure-Rust backend (moxcms), rendering intent selection, soft proofing configuration, and output intent policies — all the primitives a document editor, prepress tool, or print-aware renderer needs.

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Features

• Pure Rust ICC transforms via moxcms — no C toolchain, no liblcms2 system dependency, cross-compiles cleanly to Android and WASM targets
• CMYK and multi-ink color values with f32 component precision
• Named color spaces — sRGB, Display P3, Adobe RGB (1998), ProPhoto RGB, CMYK (generic and profile-bound)
• Rendering intents — Perceptual, Relative Colorimetric, Saturation, Absolute Colorimetric
• Soft proofing configuration — proof profile, simulation intent, gamut warning, paper simulation
• Document color policy — named output intent, fallback profile, per-document color state
• Profile-to-profile transforms — CMYK↔RGB, RGB↔RGB, Lab↔RGB, Gray↔RGB
• no_std compatible (with moxcms backend, disable default features)

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Installation

[dependencies]
appthere-color = "0.1"

No system libraries required. Everything is pure Rust.

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Quick Start

Color values

use appthere_color::{ColorValue, CmykColor, RgbColor};

// RGB color (0.0–1.0 components)
let red = ColorValue::Rgb(RgbColor::new(1.0, 0.0, 0.0));

// CMYK ink values (0.0–1.0 per channel)
let rich_black = ColorValue::Cmyk(CmykColor::new(0.60, 0.50, 0.50, 1.0));

// Lab color (D50 whitepoint)
let lab = ColorValue::Lab { l: 53.39, a: 80.09, b: 67.20 };

ICC profile transforms

use appthere_color::{IccProfile, ColorTransform, RenderingIntent};

let fogra39 = IccProfile::from_bytes(include_bytes!("profiles/ISOcoated_v2_300_eci.icc"))?;
let srgb = IccProfile::srgb();

let transform = ColorTransform::new(&fogra39, &srgb, RenderingIntent::RelativeColorimetric)?;

let cmyk_pixel = [0.60f32, 0.50, 0.50, 1.0];
let rgb_pixel = transform.transform_cmyk_to_rgb(&cmyk_pixel)?;

Soft proofing

use appthere_color::{ProofingConfig, GamutWarning, RenderingIntent};

let config = ProofingConfig::builder()
    .output_profile(fogra39)
    .simulation_intent(RenderingIntent::RelativeColorimetric)
    .display_profile(srgb)
    .gamut_warning(GamutWarning::Color([1.0, 0.0, 1.0])) // magenta flag
    .paper_simulation(true)
    .build()?;

let proofing_transform = config.build_transform()?;

Document color policy

use appthere_color::{ColorPolicy, OutputIntent};

let policy = ColorPolicy::builder()
    .output_intent(OutputIntent::named("FOGRA39", fogra39_profile))
    .default_rendering_intent(RenderingIntent::Perceptual)
    .fallback_profile(IccProfile::srgb())
    .build();

// Serialize the policy into your document format's color metadata

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Color Value Types

Type	Channels	Range	Notes
RgbColor	R, G, B	0.0–1.0	Linear or gamma-encoded depending on profile
CmykColor	C, M, Y, K	0.0–1.0	Profile-bound ink percentages
LabColor	L, a, b	L: 0–100, a/b: ±128	D50 whitepoint
XyzColor	X, Y, Z	0.0–1.0 (relative)	D50
GrayColor	K	0.0–1.0
ColorValue	—	—	Enum over all of the above

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Rendering Intents

pub enum RenderingIntent {
    Perceptual,
    RelativeColorimetric,
    Saturation,
    AbsoluteColorimetric,
}

These map directly to ICC specification intents and are passed through to the moxcms transform engine without modification.

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Soft Proofing

Soft proofing simulates how a document will appear when reproduced on a specific output device (typically a press or printer). appthere-color models proofing as a first-class configuration object rather than a transform flag:

pub struct ProofingConfig {
    pub output_profile: IccProfile,
    pub simulation_intent: RenderingIntent,
    pub display_profile: IccProfile,
    pub display_intent: RenderingIntent,
    pub gamut_warning: GamutWarning,
    pub paper_simulation: bool,
}

Soft proofing is implemented as two chained transforms internally: source → output simulation space, then simulation space → display. This is semantically equivalent to LCMS2's proofing transform and produces the same result for standard workflows.

Gamut warning modes

pub enum GamutWarning {
    /// Do not flag out-of-gamut colors
    None,
    /// Replace out-of-gamut colors with a fixed indicator color
    Color([f32; 3]),
    /// Reduce saturation of out-of-gamut colors by a factor
    Desaturate(f32),
}

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ICC Profile Support

Profiles are loaded from raw ICC bytes and backed by moxcms:

// From bytes (e.g. embedded in a document or file)
let profile = IccProfile::from_bytes(&icc_bytes)?;

// From a file path
let profile = IccProfile::from_file("path/to/profile.icc")?;

// Built-in virtual profiles
let srgb   = IccProfile::srgb();
let linear = IccProfile::linear_srgb();
let gray   = IccProfile::gray_d50();

Supported transform combinations mirror moxcms capabilities: CMYK↔RGB, RGB↔RGB, Lab↔RGB, Gray↔RGB, and any Display Class profiles up to 16 inks.

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Document Color Policy

A ColorPolicy captures the color management configuration for an entire document — the intended output condition, rendering intent, and fallback behavior when profiles are unavailable. This concept appears in PDF/X (OutputIntent), ODF (draw:color-profile), and EPUB (embedded ICC in images), but appthere-color represents it format-agnostically:

pub struct ColorPolicy {
    pub output_intent: Option<OutputIntent>,
    pub default_rendering_intent: RenderingIntent,
    pub fallback_profile: IccProfile,
    pub embedded_profiles: HashMap<String, IccProfile>,
}

Format-specific serialization (e.g. writing an /OutputIntents array into a PDF or the color profile metadata into an ODF package) is the responsibility of the document format crate that depends on appthere-color.

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Why not lcms2?

lcms2 is an excellent crate wrapping the mature Little CMS 2 library. If you need spot color (NamedColorList), DeviceLink profiles, or maximum compatibility with exotic real-world ICC profiles, it may be the right choice.

appthere-color uses moxcms instead because:

• No C toolchain required — clean cross-compilation to Android, WASM, and musl targets without a system liblcms2
• Pure Rust safety guarantees — no unsafe FFI surface
• Simpler CI — no need to manage native library availability across platforms

The tradeoff: moxcms does not yet support spot/named color lookups or some exotic DeviceLink profile classes. For document authoring workflows targeting standard RGB and CMYK output conditions, this is not a practical limitation.

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no_std Support

appthere-color is no_std compatible. Disable the default std feature:

[dependencies]
appthere-color = { version = "0.1", default-features = false }

ICC file loading from paths requires std. Profile construction from &[u8] and all transform operations work in no_std environments.

License

Licensed under the Apache License, Version 2.0.

moxcms is also Apache 2.0. The full dependency tree is permissively licensed.

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Contributing

Issues and pull requests are welcome. The scope of this crate is intentionally narrow — document-authoring color primitives and ICC transforms. Requests for PDF/ODF/EPUB serialization belong in the respective format crates.