Extraction JSON · onepdf docs

The JSON form of text extraction: glyphs, words, lines and blocks per page. It is written by PdfExtractionJson (ToJson, Write) and is meant to be compared byte for byte across implementations, so it is versioned and fully deterministic.

Format: onepdf.extraction, version 1. A reader must check both members. Additive changes (new members) keep the version; renaming, removing or changing the meaning of a member raises it.
Encoding: UTF-8, no byte-order mark. Strings are escaped as JSON requires and nothing more (non-ASCII text is written as it is). Unpaired surrogates in glyph text have been replaced by U+FFFD before writing.
Numbers: coordinates and sizes are rounded to three decimals (ties to even), written in invariant form without an exponent and without trailing zeros; negative zero is written 0. Integers are plain.
Member order is the order below. Whitespace is insignificant (the writer can indent).

Coordinate space

All coordinates are in upright page space: points, origin at the bottom-left of the page as a viewer shows it (page /Rotate and box already applied), y up. A box is [left, bottom, right, top].

Shape

{
  "format": "onepdf.extraction",
  "version": 1,
  "pageCount": <int>,
  "pages": [ Page, ... ]
}
 
Page = {
  "index": <int>,                    zero-based page index
  "width": <number>, "height": <number>,
  "usedStructureTree": <bool>,       true when the structure tree decided the order
  "diagnostics": [ <string>, ... ],  notes about this page (for example a structure tree that covered too little)
  "text": <string>,                  the page's reading-order plain text: blocks separated by "\n\n", lines by "\n", table cells by "\t"
  "blocks": [ Block, ... ],          reading order
  "glyphs": [ Glyph, ... ]           omitted when the writer is asked not to include glyphs
}
 
Block = {
  "role": "body" | "header" | "footer",
  "table": <bool>,                   a grid of short cells; lines are rows
  "bounds": [l, b, r, t],
  "lines": [ Line, ... ]
}
 
Line = {
  "direction": "ltr" | "rtl",        base direction used to put the line in logical order
  "vertical": <bool>,                vertical writing
  "bounds": [l, b, r, t],
  "cells": [ <int>, ... ],           indices into "words" where a cell (a run set apart by a wide gap) starts; first is 0
  "text": <string>,                  words joined by " ", cells by "\t"
  "words": [ Word, ... ]             logical order (right to left on the page for right-to-left text)
}
 
Word = {
  "text": <string>,                  logical order
  "bounds": [l, b, r, t],
  "visible": <bool>,                 false when every glyph is invisible
  "glyphs": [ <int>, ... ]           indices into the page's "glyphs", visual order along the reading direction
}
 
Glyph = {
  "text": <string>,                  Unicode (after ligature decomposition and /ActualText substitution; may be empty)
  "font": <string> | null,
  "fontId": <int>,                   -1 when unknown
  "size": <number>,                  em size in points
  "matrix": [a, b, c, d, e, f],      glyph space (em) to page space
  "advance": <number>,               em units along the writing direction
  "bounds": [l, b, r, t],
  "vertical": <bool>,
  "color": "#rrggbb" | null,         fill colour
  "renderMode": <int>,               0 to 7
  "visible": <bool>,                 false for invisible text (render mode 3, OCR layers)
  "mcid": <int>                      marked-content id, -1 for none
}

The glyphs listed are the ones that took part in extraction: clipped and off-page glyphs and duplicates (fake bold) are already gone unless the options kept them, and a glyph inside an /ActualText span carries the replacement text (first glyph) or empty text.