fv/lib/find_barcodes.js

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

// Generated by CoffeeScript 2.3.1
var QUIETZONE_WIDTH, boundingBox, cloneWithQuietZone, detectCandidates, dv;

dv = require('dv');

({boundingBox} = require('./math'));

// Width of the quiet zone around a barcode.
QUIETZONE_WIDTH = 35;

// Find potential barcodes in *image*.
detectCandidates = function(image) {
  var blobImage, blobMap, blobMask;
  blobImage = image.thin('bg', 8, 5).dilate(5, 3);
  blobMap = blobImage.distanceFunction(8);
  blobMask = blobMap.threshold(10).invert().dilate(42, 22);
  return blobMask.connectedComponents(8);
};

// Clone image with artificial quiet zone.
cloneWithQuietZone = function(image, rect) {
  var clone, cropped;
  cropped = image.crop(rect);
  clone = new dv.Image(cropped.width + QUIETZONE_WIDTH * 2, cropped.height + QUIETZONE_WIDTH * 2, cropped.depth);
  clone.clearBox(0, 0, clone.width, clone.height);
  clone.drawImage(cropped, QUIETZONE_WIDTH, QUIETZONE_WIDTH, cropped.width, cropped.height);
  return clone;
};

// Find all barcodes in *image* using the given *zxing* instance.
// Always returns an array; see `zxing.findCode()` for format.
module.exports.findBarcodes = function(image, zxing) {
  var candidate, clearedImage, code, codes, couldBeRotated, grayImage, i, len, point, ref;
  clearedImage = new dv.Image(image);
  grayImage = image.toGray();
  codes = [];
  ref = detectCandidates(grayImage);
  for (i = 0, len = ref.length; i < len; i++) {
    candidate = ref[i];
    try {
      couldBeRotated = candidate.height * 1.75 > candidate.width;
      zxing.image = cloneWithQuietZone(grayImage, candidate);
      zxing.tryHarder = couldBeRotated;
      code = zxing.findCode();
      // Test if its worth a retry using some image morphing magic.
      if ((code == null) && candidate.width < 0.3 * grayImage.width) {
        // Apply some magic image morphing and retry.
        zxing.image = zxing.image.scale(2).open(5, 3).scale(0.5).otsuAdaptiveThreshold(400, 400, 0, 0, 0.1).image;
        code = zxing.findCode();
      }
      if (code != null) {
        // Test if removal is sane.
        if (candidate.width < 0.3 * grayImage.width) {
          clearedImage.clearBox(candidate);
        }
        code.box = boundingBox((function() {
          var j, len1, ref1, results;
          ref1 = code.points;
          results = [];
          for (j = 0, len1 = ref1.length; j < len1; j++) {
            point = ref1[j];
            results.push({
              x: point.x,
              y: point.y,
              width: 1,
              height: 1
            });
          }
          return results;
        })());
        if (code.box.width < 20) {
          code.box.y -= QUIETZONE_WIDTH;
          code.box.x -= Math.round(candidate.width / 2);
          code.box.width += candidate.width;
          code.box.height += QUIETZONE_WIDTH * 2;
        }
        if (code.box.height < 20) {
          code.box.x -= QUIETZONE_WIDTH;
          code.box.y -= Math.round(candidate.height / 2);
          code.box.height += candidate.height;
          code.box.width += QUIETZONE_WIDTH * 2;
        }
        code.box.x += candidate.x - QUIETZONE_WIDTH;
        code.box.y += candidate.y - QUIETZONE_WIDTH;
        delete code.points;
        codes.push(code);
      }
    } catch (error) {}
  }
  return [codes, clearedImage];
};