krilla

The krilla library provides a wide range of 2D graphics capabilities for PDF generation:

• Paths & Shapes: Filling and stroking arbitrary paths, clip paths, and affine transformations.
• Text: A high-level API for rendering character sequences and a low-level API for positioned glyphs. Includes excellent OpenType font support (including color fonts).
• Color & Effects: Alpha and luminosity masks, blend modes, layer isolation, and various gradients (linear, radial, sweep) and patterns.
• Images: Embedding bitmap images and SVG images (via the krilla-svg crate).
• Performance: Optional multi-threading support via rayon for faster compression and image processing.

PDF Specification Support

• Document Structure: Document outlines, page labels, annotations, links, and (named) destinations.
• Metadata & Accessibility: Document metadata and support for creating accessible PDFs via tagged PDF.
• Versions & Standards: Supports PDF versions 1.4 through 2.0, and validated export modes including PDF/A-1, PDF/A-2, PDF/A-3, PDF/A-4, and PDF/UA-1.

When using krilla in PDF/A-4 export mode, the library enforces PDF version 2.0. This mode is designed for long-term archiving and has specific constraints and capabilities:

Core Capabilities

• Graphics: Supports transparency and device-independent colors using compatible ICC profiles (RGB only for output intents).
• Fonts: Uses IDENTITY-H encoding, embeds CIDtoGIDMap for Type2 CID fonts, embeds cmaps, font programs, and ToUnicode entries. It ensures Unicode values are valid (not U+FEFF or U+FFFE) and forbids characters in the private use area.
• Metadata: Always requires metadata and includes document identifiers and minimal xmpMM:History entries.
• Annotations: Only supports link annotations.

Limitations and Unsupported Features

• Security: No support for encryption, permissions, or digital signatures.
• Interactivity: No support for interactive forms, JavaScript actions, or named actions.
• Images: No support for JPEG2000, thumbnails, or the Interpolate key. Inline images are not used.
• Advanced PDF Features: No support for linearization, 3D features, geospatial features, or optional content.
• Embedded Files: By default, embedding files is forbidden in PDF/A-4 mode (see A4-F/A4-E for exceptions).

You can style shapes and text using surface.set_fill. The Fill struct accepts a paint which can be a solid color or a gradient.

Solid Colors

Use krilla::color::rgb::Color converted into a paint type.

Linear Gradients

Use LinearGradient to define a gradient between two points (x1, y1 to x2, y2). It requires a list of Stop objects, where each stop defines an offset (using NormalizedF32), a color, and an opacity.

use krilla::paint::{LinearGradient, Stop, Fill, FillRule, SpreadMethod};
use krilla::num::NormalizedF32;
use krilla::color::rgb;

let lg = LinearGradient {
    x1: 60.0,
    y1: 0.0,
    x2: 140.0,
    y2: 0.0,
    transform: Default::default(),
    spread_method: SpreadMethod::Repeat,
    stops: vec![
        Stop {
            offset: NormalizedF32::new(0.2).unwrap(),
            color: rgb::Color::new(255, 0, 0).into(),
            opacity: NormalizedF32::ONE,
        },
    ],
    anti_alias: false,
};

surface.set_fill(Some(Fill {
    paint: lg.into(),
    rule: FillRule::EvenOdd,
    opacity: NormalizedF32::ONE
}));

Krilla uses a color-coded legend to document how it handles various compliance properties and invariants. When reviewing documentation in the configure directory, use the following legend to understand what is actively enforced, what is unsupported, and what is the responsibility of the user:

• 🟢 Actively Enforced: Krilla checks this property via code invariants or by returning errors if the property is not fulfilled.
• 🔵 Unsupported: Krilla fulfills this property simply because the feature is not supported.
• 🟣 User Responsibility: Krilla cannot enforce this property; the user of the library must ensure compliance.
• 🔴 Not Enforced: The property is currently not enforced by krilla.
• 🟠 Undecided/Deferred: The property might be documented or checked in the future, but is currently ignored because it is deemed unnecessary or difficult to implement.
• - Not Applicable: The property does not apply to krilla (e.g., it is not a reader application).