settings.jsonc

{
    // ===== Paths =====
    // Directory containing the jbig2enc binary (bundled in deps/jbig2enc).
    "native.dir": "./deps/jbig2enc",

    // ===== PDF Rendering =====
    // DPI for rendering PDF pages to images before compression.
    //   300 = standard quality
    //   200 = faster, smaller output
    //   600 = high resolution (≈4x the memory of 300; raise the JVM heap and/or
    //         lower pipeline.maxThreads to avoid running out of memory)
    "rendering.dpi": 300,

    // ===== Image Segmentation =====
    // Tile size (px) for background normalization grid.
    // Smaller = more detail; larger = faster.
    "segmenter.tileSize": 64,

    // Background-level percentile per tile (0.0 - 1.0).
    // 0.95 = 95th percentile.  Increase for sparse text.
    "segmenter.percentile": 0.95,

    // Inpainting propagation radius (px) for filling text regions.
    // <= 0 = infinite (propagate to every foreground pixel; no white blobs).
    // > 0 = bounded (pixels farther away are filled white).
    "segmenter.inpaintRadius": 0,

    // Thresholding mode: "sauvola" or "otsu".
    //   sauvola (default): per-pixel local adaptive threshold from the mean/stddev
    //     of a small window (sauvolaWindow/K/R). Use for scanned or photographed
    //     pages with uneven illumination, shadows, gradients, or faint/low-contrast
    //     text — it keeps thin strokes that a single global threshold would miss.
    //   otsu: one global threshold over the whole normalized page. Faster, and good
    //     for clean, uniformly lit, high-contrast pages (printed text on white);
    //     it tends to drop faint text or over-segment busy backgrounds.
    // When in doubt, start with sauvola; try otsu if sauvola captures too much
    // background noise (speckle) on otherwise clean pages.
    "segmenter.thresholdMode": "sauvola",

    // Sauvola local window side (px). Integral images keep this cheap.
    "segmenter.sauvolaWindow": 15,

    // Sauvola sensitivity (0.1 - 0.5). Higher = more aggressive foreground.
    "segmenter.sauvolaK": 0.20,

    // Sauvola dynamic range of the image (typical 128 for 8-bit gray).
    "segmenter.sauvolaR": 128,

    // Connected-component filtering: dark regions larger than these limits are
    // treated as pictures/logos and left in the (color) background instead of
    // the JBIG2 mask. Fractions of page area / larger page dimension. 0 disables.
    "segmenter.maxComponentArea": 0.005,
    "segmenter.maxComponentDim": 0.10,

    // ===== Pipeline =====
    // Maximum worker threads for page preparation (rendering is always
    // sequential; segmentation + text extraction + image IO run in parallel).
    // 0 = auto (use all available processors).  Override via --threads.
    // The pipeline keeps up to (threads + 2) pages in memory at once; at high
    // DPI (e.g. 600) each page needs ~1 GB, so cap this and raise the JVM heap.
    "pipeline.maxThreads": 0,

    // ===== MRC =====
    // Enable Mixed Raster Content compression.
    //   true  = segment background (JPEG) + foreground (JBIG2) + text layer
    //   false = original images (JPEG) + text layer only (no MRC compression)
    "pipeline.mrc.enabled": true,

    // Background downscale factor for MRC (0.1 - 1.0).
    //   0.33 = 3x downsampling (e.g., 300 DPI → ~100 DPI background)
    //   1.0  = no downsampling (full resolution)
    // Text sharpness is preserved by the foreground mask layer.
    // Override via --bg-scale CLI flag.
    "pipeline.mrc.backgroundScale": 0.33,

    // Background JPEG quality when a foreground mask is present (0.1 - 1.0).
    //   0.50 = default (text pixels come from the sharp mask, not the JPEG)
    //   0.90 = higher quality background, larger file
    // Override via --jpeg-quality CLI flag.
    "pipeline.mrc.jpegQuality": 0.50,

    // Background JPEG quality when MRC is OFF (no foreground mask, so the
    // background is the only visual layer). 0.1 - 1.0.
    //   0.85 = default (good fidelity for full-resolution page images)
    //   1.0  = near-lossless, larger file
    // Ignored when "pipeline.mrc.enabled" is true. Override via --jpeg-quality.
    "pipeline.jpegQuality": 0.85,

    // Pre-encode Gaussian blur sigma for MRC background (0 = off).
    //   0.8  = mild smoothing (reduces JPEG artifacts, improves compression)
    //   0    = no smoothing
    // Safe because text edges come from the mask, not the background.
    "pipeline.mrc.bgSmoothSigma": 0.8,

    // True MRC foreground color plane: the binary mask becomes a soft mask
    // (SMask) over a downsampled copy of the original page, so text pixels keep
    // their original color instead of flat black.
    //   false = black stencil (default, smaller, PDF/A compatible)
    //   true  = color text (soft masks are NOT allowed in PDF/A-2b)
    // Override via --fg-color CLI flag.
    "pipeline.mrc.foregroundColor": false,

    // Downsample factor for the foreground color plane (0.1 - 1.0).
    //   0.5  = 2x downsampling (default; good balance of size and color fidelity)
    //   0.25 = 4x downsampling (smaller, but thin dark strokes may wash out)
    //   1.0  = full resolution (largest file, best fidelity)
    // The full-res binary mask keeps text edges sharp regardless of this factor.
    "pipeline.mrc.foregroundScale": 0.5,

    // JPEG quality for the foreground color plane (0.1 - 1.0).
    "pipeline.mrc.foregroundJpegQuality": 0.7,

    // ===== JBIG2 Compression =====
    // Flags passed to the jbig2enc binary.
    //   -p = global symbol dictionary
    //   -s = refine smearing
    "jbig2enc.flags": "-p -s",

    // ===== PDF/A =====
    // Enable PDF/A-2b output (adds XMP metadata, sRGB OutputIntent).
    // Override via --pdfa CLI flag.
    "pdf.pdfa.enabled": false,

    // Path to a TrueType font file for embedding into PDF/A output.
    // Required for strict PDF/A compliance (Standard 14 fonts are not embedded).
    // When empty, falls back to Standard 14 fonts (non-embedded).
    "pdf.pdfa.fontPath": "",

    // ===== PDF Assembly =====
    // Path to a TrueType/OpenType font for the invisible text layer.
    // Required for CJK characters (Chinese, Japanese, Korean).
    // When empty, auto-detects the bundled font (deps/fonts) or a system
    // CJK font if the extracted text contains CJK characters.
    "pdf.fontPath": "",

    // Standard 14 font for the invisible text layer (Latin-only).
    // The Standard 14 are Type1 fonts guaranteed in every PDF viewer
    // (defined by the PDF spec), so they never need embedding, keeping
    // the output file small.
    //
    //   Family         | Variants
    //   ---------------+--------------------------
    //   Times-Roman    | Regular, Bold, Italic, BoldItalic
    //   Helvetica      | Regular, Bold, Italic, BoldItalic
    //   Courier        | Regular, Bold, Italic, BoldItalic
    //   Symbol         | Regular
    //   ZapfDingbats   | Regular
    //
    "pdf.font": "HELVETICA",

    // Minimum font size (pt) to prevent zero-size fonts.
    "pdf.minFontSize": 1,

    // Producer string for the output PDF metadata.
    // If the input PDF has a Producer, the output will be "<input> -> <producer>".
    // If the input has no Producer, the output will be the string below.
    "pdf.producer": "MrcPdf",

    // ===== Output =====
    // Default output PDF path.
    // Override via -o / --output CLI flag.
    "output.file": "output.pdf"
}