lmpdf

Safe, ergonomic Rust bindings to PDFium — Google's open-source PDF renderer. Load PDFs from files or memory, render pages to bitmaps, and export images with a builder-style API and zero raw pointers in user code.

Features

• Dynamic loading — load libpdfium at runtime; no compile-time linking required
• Safe API — newtype handles and arena-based ownership eliminate use-after-free and double-free classes of bugs
• Render to bitmap — render any page to BGRA/BGR/grayscale pixel buffers with configurable scale, rotation, max dimensions, and render flags
• Image export — optional image feature converts bitmaps directly to image::DynamicImage for saving as PNG, JPEG, etc.
• Version-gated bindings — target specific PDFium releases (pdfium_7811, pdfium_7763, pdfium_7543) or use pdfium_latest
• Proc-macro generated FFI — a custom pdfium_ffi! macro generates both the trait definition and backend implementations, keeping bindings in sync automatically

Crate structure

Crate	Purpose
lmpdf	High-level API: Pdfium, Document, Bitmap, RenderConfig
lmpdf-sys	Raw FFI bindings (via bindgen), safe wrappers, dynamic loading
lmpdf-sys-macros	Proc-macro that generates PdfiumBindings trait + backends
lmpdf-bundle	Helpers for bundling a PDFium binary with your application

Quick start

Prerequisites

Download a pre-built PDFium binary for your platform from pdfium-binaries (or build from source). Set the PDFIUM_PATH environment variable to the shared library path.

Usage

Add lmpdf to your Cargo.toml:

[dependencies]
lmpdf = { git = "https://github.com/tlkahn/lmpdf.git" }

Render every page of a PDF to PNG (the default config renders at 144 DPI with high-quality flags):

use lmpdf::{Pdfium, RenderConfig};
use std::path::PathBuf;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let pdfium = Pdfium::open(std::env::var("PDFIUM_PATH")?)?;
    let doc = pdfium.open_document("input.pdf", None)?;
    let config = RenderConfig::new(); // 144 DPI, PRINTING + LCD_TEXT + ANNOTATIONS

    for i in 0..doc.page_count() {
        let page = doc.page(i)?;
        let bitmap = doc.render_page(page, &config)?;
        let img = bitmap.to_image(); // requires `image` feature
        img.save(PathBuf::from(format!("page_{}.png", i + 1)))?;
    }
    Ok(())
}

Render configuration

RenderConfig uses a builder pattern for full control over output:

use lmpdf::{RenderConfig, RenderFlags, Rotation};
use lmpdf::BitmapFormat;

let config = RenderConfig::new()
    .dpi(300)                           // 300 DPI (default is 144)
    .max_width(4096)                    // clamp width, preserve aspect ratio
    .rotation(Rotation::Degrees90)      // rotate 90°
    .format(BitmapFormat::Bgr)          // 24-bit BGR (no alpha)
    .flags(RenderFlags::PRINTING | RenderFlags::ANNOTATIONS)
    .background_color(0xFFFFFFFF);      // white

Building from source

git clone https://github.com/tlkahn/lmpdf.git
cd lmpdf
cargo build --workspace
cargo test --workspace

bindgen requires libclang — on Debian/Ubuntu: sudo apt install libclang-dev.

Roadmap

• Text extraction API
• Form filling support
• Annotation reading/writing
• Static linking support (lmpdf-bundle)
• WASM backend (groundwork in gen_wasm.rs)
• crates.io publishing

License

PDFium is licensed under the Apache License 2.0 and the BSD 3-Clause License. See the PDFium project for details.