fv/lib/match_barcodes.js

FormVision is a node.js library for extracting data from scanned forms

// Generated by CoffeeScript 2.3.1
var barcodeToValue, center, distanceVector, length, unpack, validate;

({unpack, validate} = require('./schema'));

({distanceVector, length, center} = require('./math'));

barcodeToValue = function(barcode) {
  return {
    type: barcode.type,
    data: barcode.data,
    buffer: barcode.buffer
  };
};

// Match barcode data to form schema.
module.exports.matchBarcodes = function(formData, formSchema, barcodes, schemaToPage) {
  var barcode, barcodeFields, choice, confidence, distance, field, fieldData, i, j, k, len, len1, len2, matchMap, matches, name, projection, radius, validFields, value, values;
  barcodeFields = formSchema.fields.filter(function(field) {
    return field.type === 'barcode';
  });
  // Map barcodes and fields to matches.
  matchMap = {};
  for (i = 0, len = barcodes.length; i < len; i++) {
    barcode = barcodes[i];
    value = barcodeToValue(barcode);
    validFields = barcodeFields.filter(function(field) {
      return validate(field, value, false);
    });
    for (j = 0, len1 = validFields.length; j < len1; j++) {
      field = validFields[j];
      // If searchRadius is set, additionally filter matches by distance
      if (field.searchRadius > 0) {
        projection = schemaToPage(field.box);
        distance = length(distanceVector(center(projection), center(barcode.box)));
        radius = Math.max(projection.width, projection.height) / 2;
        if (distance > radius * field.searchRadius) {
          continue;
        }
      }
      if (matchMap[name = field.path] == null) {
        matchMap[name] = [];
      }
      matchMap[field.path].push({
        barcode: barcode,
        paths: validFields.map(function(field) {
          return field.path;
        })
      });
    }
  }
// Reduce matches to fields.
  for (k = 0, len2 = barcodeFields.length; k < len2; k++) {
    field = barcodeFields[k];
    if (matchMap[field.path] != null) {
      matches = matchMap[field.path];
      // Many barcodes to one field resolution.
      if (matches.length > 1 && (field.fieldSelector != null)) {
        values = matches.map(function(match) {
          return barcodeToValue(match.barcode);
        });
        choice = field.fieldSelector(values);
        confidence = 100;
        if (!(choice in values)) {
          throw new Error('Returned choice index out of bounds');
        }
      } else {
        choice = 0;
        confidence = 100 / matches.length;
      }
      // Assign to field.
      fieldData = unpack(formData, field.path);
      fieldData.value = barcodeToValue(matches[choice].barcode);
      fieldData.confidence = confidence;
      fieldData.box = matches[choice].barcode.box;
      fieldData.conflicts = matches[choice].paths.filter(function(path) {
        return path !== field.path;
      });
    } else {
      fieldData = unpack(formData, field.path);
      fieldData.confidence = 0;
      fieldData.box = schemaToPage(field.box);
      fieldData.conflicts = [];
    }
  }
};