rasterrocket

Pure Rust PDF → pixels pipeline. Zero Poppler, zero subprocesses, zero Leptonica in the render path.

Renders PDF pages to 8-bit grayscale pixel buffers for direct consumption by Tesseract OCR or any other downstream consumer. No intermediate files.

# Cargo.toml — library
rasterrocket = "1.0"

# CLI — drop-in pdftoppm replacement
cargo install rasterrocket-cli

What's new in v1.0.0

• Spec-correct simple-font text. The Widths-array lookup now prevails over FreeType metrics for all embedded and non-embedded simple fonts, per PDF §9.2.4. Academic and English-language PDFs show the largest improvement: avg RMSE vs pdftoppm dropped 17–19 points on corpus-05 and corpus-14.
• Vulkan compute backend. --features vulkan or --backend vulkan runs AA fill, tile fill, and parallel-Huffman JPEG decode on any Vulkan 1.3+ device — NVIDIA, AMD, Intel, or Apple via MoltenVK. Verified on RTX 5070; cross-vendor smoke pending hardware. Under auto, Vulkan is preferred over CUDA when both are compiled in (faster process init on single-session workloads).
• Process-static GPU init. The CUDA and Vulkan contexts are initialised once per process (not once per open_session). Short-lived multi-document pipelines no longer pay ~240 ms per document.
• PDF_RASTER_BACKEND env var. Switch backends at runtime without recompiling. Valid values: auto, cpu, cuda, vaapi, vulkan. The CLI --backend flag takes precedence.
• Parallel-Huffman JPEG. GPU-accelerated Huffman decode (gpu-jpeg-huffman feature, implied by vulkan) is wired into the production decode path. Dormant by default (threshold = u32::MAX); enable with PDF_RASTER_HUFFMAN_THRESHOLD=0 for benchmarking.
• RasterOptions::default() — dpi = 300, first_page = 1, last_page = u32::MAX, deskew = false, pages = None. Use ..RasterOptions::default() to fill unset fields.
• PageSet — render a sparse subset of pages without visiting intermediate ones.

use rasterrocket::{RasterOptions, raster_pdf};

let opts = RasterOptions { dpi: 300.0, ..RasterOptions::default() };

for (page_num, result) in raster_pdf(Path::new("scan.pdf"), &opts) {
    let page = result?;
    // page.pixels — Vec<u8>, 8-bit greyscale, width × height, top-to-bottom
    // page.effective_dpi — pass to your OCR engine (accounts for PDF UserUnit scaling)
    // See the OCR Integration wiki for Tesseract, ocrs, Google Cloud Vision, and GPT-5 patterns.
}

Documentation

Crates

Hardware compatibility

CPU: x86-64 (AMD and Intel) and aarch64 (ARM). AVX2/AVX-512 on x86-64; NEON (and SVE2 on nightly) on aarch64. Build with -C target-cpu=native to enable AVX-512 or native NEON width.

GPU (optional):

• NVIDIA via CUDA 12 or 13 — full feature set (nvJPEG, nvJPEG2000, AA fill, ICC CLUT, ICC matrix, deskew, image cache). cudarc is pinned to the cuda-12080 driver-API binding so the same source builds against both 12.x and 13.x drivers (forward-compatible per the CUDA driver-API ABI).
• Cross-vendor via Vulkan compute — AA fill, tile fill, and parallel-Huffman JPEG decode kernels run on any Vulkan 1.3+ device (NVIDIA, AMD, Intel, Apple via MoltenVK). Verified on RTX 5070; cross-vendor smoke pending hardware. No nvJPEG / cache support under Vulkan today (JPEG decode goes through the GPU parallel-Huffman path, not nvJPEG).
• Linux iGPU/dGPU via VA-API — JPEG baseline decode on AMD VCN, Intel Quick Sync, Intel Arc.

All GPU features fall back to CPU automatically when unavailable. AMD/Radeon ROCm and Apple Metal-native backends are not implemented (Vulkan covers Apple via MoltenVK).

Build

# CPU-only (no CUDA)
cargo build --release -p rasterrocket-cli

# With all GPU features (CUDA 12 or 13 toolkit, NVIDIA GPU required)
# Default CUDA_ARCH is sm_80 (Ampere); override for older or newer GPUs.
CUDA_ARCH=sm_120 cargo build --release -p rasterrocket-cli \
  --features "rasterrocket/nvjpeg,rasterrocket/nvjpeg2k,rasterrocket/gpu-aa,rasterrocket/gpu-icc,rasterrocket/gpu-deskew,rasterrocket/cache"

# With Vulkan compute backend (cross-vendor; no NVIDIA dependency).
# Requires the LunarG Vulkan SDK on the build host (slangc compiles the
# .slang shaders to SPIR-V).  Vulkan 1.3+ ICD on the runtime host.
cargo build --release -p rasterrocket-cli --features "rasterrocket/vulkan"

Picking CUDA_ARCH for your GPU

The CUDA_ARCH environment variable controls which Compute Capability the PTX kernels target. Mismatched arch flags produce kernels the GPU can't load at runtime. Set it to your card's CC (e.g. sm_75, sm_86, sm_120).

Look up your card's exact Compute Capability at developer.nvidia.com/cuda-gpus. The build defaults to sm_80 if CUDA_ARCH is unset; that's a reasonable fallback for any Ampere-or-later card thanks to PTX forward-compatibility, but matching your hardware exactly produces better-optimised code.

Feature flags

All GPU features fall back to CPU automatically when the runtime requirement is missing, except --backend cuda / --backend vulkan / --backend vaapi which fail loudly with a clear error.

Backend selection

The runtime backend is chosen from three sources, in priority order:

1. The CLI --backend {auto,cpu,cuda,vaapi,vulkan} flag.
2. The PDF_RASTER_BACKEND environment variable (same valid values).
3. The compile-time default — auto.

Under auto, when both backends are compiled in, Vulkan is preferred over CUDA. Vulkan's per-process init is faster and the kernel dispatch is comparable on the workloads that matter; CUDA wins narrowly when the device-resident cache feature is firing and amortising across many pages from one session. Both backends fall through to CPU when their runtime is unavailable; --backend cuda / --backend vulkan make the failure loud instead.

# Ship a Vulkan-default binary, override per-process when you need CUDA:
PDF_RASTER_BACKEND=cuda rrocket input.pdf out

# CLI flag always wins over the env var:
PDF_RASTER_BACKEND=cuda rrocket --backend cpu input.pdf out   # uses CPU

Compile cache (sccache) — optional

.cargo/config.toml sets SCCACHE_CACHE_MULTIARCH=1 so -C target-cpu=native builds can be cached, but the wrapper itself is opt-in: plain cargo build works without sccache. To enable:

cargo install sccache       # one-time install
export RUSTC_WRAPPER=sccache # add to ~/.bashrc to make it permanent

Shared with any other Rust project on the same machine that opts in — cross-project cache keys don't collide (sccache hashes the full compiler args). Verify with sccache --show-stats (a healthy hit-rate after the first build is ≥ 70%). Do not rsync ~/.cache/sccache between machines with different CPUs — target-cpu=native resolves differently per arch.

Testing

# Unit tests (always filter by module, never run unfiltered)
cargo test -p rasterrocket --lib -- deskew
cargo test -p rasterrocket-gpu --lib -- icc

# Pixel-diff comparison against pdftoppm (requires release build in PATH)
tests/compare/compare.sh -r 150 tests/fixtures/input.pdf

Performance

Benchmarks vs Poppler's pdftoppm on a 10-document corpus at 150 DPI. Full methodology, hardware details, and AVX2 vs AVX-512 comparison in the Benchmarks wiki page.

CPU-only (no GPU), Ryzen 9 9900X3D + AVX-512, v0.9.1, RAM-backed output, cold cache, hyperfine 5 runs:

Per-version regression history and the full pdftoppm comparison are in the Benchmarks wiki page.

GPU-accelerated (CUDA: nvJPEG + nvJPEG2000), same machine + RTX 5070 (v0.9.1):

Largest gains on scan-heavy corpora where SIMD JPEG decoding (CPU) and nvJPEG/nvJPEG2000 (GPU) dominate. Short native-text PDFs are startup-bound and show modest gains. See the Benchmarks wiki page for the full table including an Intel i7-8700K (AVX2-only) comparison.