stet-graphics

The graphics foundation for the stet PostScript and PDF rendering stack — colours, the display list, ICC profile management, and the mesh / patch shading parsers.

Only depends on stet-fonts, so it's usable on its own if any of these subsystems is what you actually want:

• ICC colour management (CMYK↔sRGB, image bulk conversion, BPC) via moxcms.
• Parsers for PDF Type 4–7 shading data (Gouraud mesh, Coons / tensor patch).
• The DisplayList / DisplayElement types — both the stet PostScript interpreter and stet-pdf-reader emit into this format, so downstream consumers (custom output devices, PDF rewriters, diff tools) use these types to stay compatible.

If you just want to render PS or PDF, use the stet facade crate instead.

What's inside

See the Display List Reference for complete element and parameter documentation.

Standalone use

[dependencies]
stet-graphics = "0.1"

ICC colour management

use stet_graphics::icc::IccCache;

let profile = std::fs::read("FOGRA39.icc")?;
let mut cache = IccCache::new();
cache.load_cmyk_profile_bytes(&profile);

// CMYK → sRGB in [0, 1]
if let Some((r, g, b)) = cache.convert_cmyk(0.0, 0.81, 1.0, 0.0) {
    println!("{r:.3} {g:.3} {b:.3}");
}

// Bulk image conversion (8-bit) — fast path for rasterization.
// `src` holds CMYK bytes; `dst` receives 8-bit sRGB.
// cache.convert_image_8bit(&src_cmyk, &mut dst_rgb, ...);
# Ok::<(), Box<dyn std::error::Error>>(())

Black-point compensation is on by default; opt out with IccCache::new_with_options(IccCacheOptions { bpc_mode: BpcMode::Off, .. }).

Parse a PDF Type 6 (Coons patch) shading

use stet_graphics::mesh_shading::parse_type6_patches;

// `data` is the decoded binary stream from a PDF shading dictionary.
// The bits-per-* arguments come from the shading dict's
// /BitsPerCoordinate, /BitsPerComponent, and /BitsPerFlag entries; the
// `decode` slice holds the flattened /Decode array (x range, y range,
// then one range per colour component).
let patches = parse_type6_patches(
    &data,
    /* bits_per_coordinate = */ 16,
    /* bits_per_component  = */ 8,
    /* bits_per_flag       = */ 2,
    /* decode              = */ &[0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0],
    /* n_components        = */ 3,
);

for patch in &patches {
    // patch.points — 12 or 16 control points (Coons uses 12)
    // patch.colors — 4 corner `DeviceColor` values
}
# Ok::<(), ()>(())

Consume a display list

The DisplayList type is shared between stet and stet-pdf-reader, so a custom output format can iterate over elements without caring which source produced them:

use stet_graphics::display_list::{DisplayList, DisplayElement};

fn summarize(list: &DisplayList) {
    let (mut fills, mut strokes, mut images) = (0, 0, 0);
    for elem in list.elements() {
        match elem {
            DisplayElement::Fill { .. }   => fills   += 1,
            DisplayElement::Stroke { .. } => strokes += 1,
            DisplayElement::Image { .. }  => images  += 1,
            _ => {}
        }
    }
    println!("{fills} fills, {strokes} strokes, {images} images");
}

License

Apache-2.0 OR MIT