a qrcode-service by nodejs

qrcode-service.js

//npm install qrcode
"use strict";
var _ = require('lodash');
var aid = require(__base + 'lib/aid');
var defaultNumber = aid.defaultNumber();

function resample_hermite(canvas, W, H, W2, H2) {
  var time1 = Date.now();
  W2 = Math.round(W2);
  H2 = Math.round(H2);
  var img = canvas.getContext("2d").getImageData(0, 0, W, H);
  var img2 = canvas.getContext("2d").getImageData(0, 0, W2, H2);
  var data = img.data;
  var data2 = img2.data;
  var ratio_w = W / W2;
  var ratio_h = H / H2;
  var ratio_w_half = Math.ceil(ratio_w / 2);
  var ratio_h_half = Math.ceil(ratio_h / 2);

  for (var j = 0; j < H2; j++) {
    for (var i = 0; i < W2; i++) {
      var x2 = (i + j * W2) * 4;
      var weight = 0;
      var weights = 0;
      var weights_alpha = 0;
      var gx_g, gx_b, gx_a;
      var gx_r = gx_g = gx_b = gx_a = 0;
      var center_y = (j + 0.5) * ratio_h;
      for (var yy = Math.floor(j * ratio_h); yy < (j + 1) * ratio_h; yy++) {
        var dy = Math.abs(center_y - (yy + 0.5)) / ratio_h_half;
        var center_x = (i + 0.5) * ratio_w;
        var w0 = dy * dy //pre-calc part of w
        for (var xx = Math.floor(i * ratio_w); xx < (i + 1) * ratio_w; xx++) {
          var dx = Math.abs(center_x - (xx + 0.5)) / ratio_w_half;
          var w = Math.sqrt(w0 + dx * dx);
          if (w >= -1 && w <= 1) {
            //hermite filter
            weight = 2 * w * w * w - 3 * w * w + 1;
            if (weight > 0) {
              dx = 4 * (xx + yy * W);
              //alpha
              gx_a += weight * data[dx + 3];
              weights_alpha += weight;
              //colors
              if (data[dx + 3] < 255)
                weight = weight * data[dx + 3] / 250;
              gx_r += weight * data[dx];
              gx_g += weight * data[dx + 1];
              gx_b += weight * data[dx + 2];
              weights += weight;
            }
          }
        }
      }
      data2[x2] = gx_r / weights;
      data2[x2 + 1] = gx_g / weights;
      data2[x2 + 2] = gx_b / weights;
      data2[x2 + 3] = gx_a / weights_alpha;
    }
  }
  //console.log("hermite = " + (Math.round(Date.now() - time1) / 1000) + " s");
  canvas.getContext("2d").clearRect(0, 0, Math.max(W, W2), Math.max(H, H2));
  canvas.width = W2;
  canvas.height = H2;
  canvas.getContext("2d").putImageData(img2, 0, 0);
  return canvas;
}

function defaultNumber(val, default_val) {
  val = +val;
  if (typeof val == 'number' && !isNaN(val)) {
    return val;
  } else {
    return default_val;
  }
}

module.exports = function (req, res) {
  var params = req.query || {};
  var QRCode = require('qrcode');
  var draw = new QRCode.QRCodeDraw();
  var Canvas = QRCode.canvas;
  var content = params['content'] || 'hello';
  var width = params['width'];
  var errorLevelObj = {//容错率等级 L M Q H
    L: 1,
    M: 0,
    Q: 3,
    H: 2
  };
  var errorlevel = params['errorlevel'] && params['errorlevel'].toUpperCase();
  var margin = +params['margin'];

  //draw.color = {
  //  dark: '#333',
  //  light: '#efefef'
  //};
  draw.scale = defaultNumber(params['scale'], 10);//黑点尺寸
  draw.defaultErrorCorrectLevel = typeof errorLevelObj[errorlevel] == 'number' ? errorLevelObj[errorlevel] : 1;
  draw.marginScaleFactor = 0;//边距点个数
  draw.defaultMargin = defaultNumber(params['margin'], 10);
  //if (_.isNumber(margin) && !_.isNaN(margin)) {//边距大小，像素
  //  draw.defaultMargin = margin;
  //} else {
  //  draw.defaultMargin = 10;
  //}

  //draw.draw(new Canvas(200, 200), content, {version: +params['level'] || 10}, function (error, canvas) {//設置容量等級
  draw.draw(new Canvas(200, 200), content, function (error, canvas) {
    if (width) {
      canvas = resample_hermite(canvas, canvas.width, canvas.height, width, width);//重置canvas大小
    }
    canvas.toDataURL(function (err, url) {//转换为二进制以图片格式输出
      url = url.replace('data:image/png;base64,', '');
      url = new Buffer(url, 'base64');
      res.type('png');
      res.end(url, 'binary');
    });
  });
};