escpos/image.js

ESC/POS Printer driver for nodejs

'use strict';
const getPixels = require('get-pixels');

/**
 * [Image description]
 * @param {[type]} pixels [description]
 */
function Image(pixels){
  if(!(this instanceof Image)) 
    return new Image(pixels);
  this.pixels = pixels;

  this.data = [];
  function rgb(pixel) {
    return {
      r: pixel[0],
      g: pixel[1],
      b: pixel[2],
      a: pixel[3]
    };
  };

  var self = this;
  for(var i=0;i<this.pixels.data.length;i+=this.size.colors){
    this.data.push(rgb(new Array(this.size.colors).fill(0).map(function(_, b){
      return self.pixels.data[ i + b ];
    })));
  };

  this.data = this.data.map(function(pixel) {
   if (pixel.a == 0) return 0;
   var shouldBeWhite = pixel.r > 200 && pixel.g > 200 && pixel.b > 200;
   return shouldBeWhite ? 0 : 1;
  });

};

/**
 * [load description]
 * @param  {[type]}   url      [description]
 * @param  {[type]}   type     [description]
 * @param  {Function} callback [description]
 * @return {[type]}            [description]
 */
Image.load = function(url, type, callback){
  if(typeof type == 'function'){
    callback = type;
    type = null;
  }
  getPixels(url, type, function(err, pixels){
    if(err) return callback(err);
    callback(new Image(pixels));
  });
};

/**
 * [description]
 * @return {[type]}     [description]
 */
Image.prototype.__defineGetter__('size', function(){
  return {
    width : this.pixels.shape[0],
    height: this.pixels.shape[1],
    colors: this.pixels.shape[2],
  };
});

/**
 * [toBitmap description]
 * @param  {[type]} density [description]
 * @return {[type]}         [description]
 */
Image.prototype.toBitmap = function(density) {
  density = density || 24;

  var ld, result = [];
  var x, y, b, l, i;
  var c = density / 8;

  // n blocks of lines
  var n = Math.ceil(this.size.height / density);

  for (y = 0; y < n; y++) {
    // line data
    ld = result[y] = [];

    for (x = 0; x < this.size.width; x++) {

      for (b = 0; b < density; b++) {
        i = x * c + (b >> 3);

        if (ld[i] === undefined) {
          ld[i] = 0;
        }

        l = y * density + b;
        if (l < this.size.height) {
          if (this.data[l * this.size.width + x]) {
            ld[i] += (0x80 >> (b & 0x7));
          }
        }
      }
    }
  }

  return {
    data: result,
    density: density
  };
};
/**
 * [toRaster description]
 * @return {[type]} [description]
 */
Image.prototype.toRaster = function () {
  var result = [];
  var width  = this.size.width;
  var height = this.size.height;
  var data   = this.data;

  // n blocks of lines
  var n = Math.ceil(width / 8);
  var x, y, b, c, i;

  for (y = 0; y < height; y++) {

    for (x = 0; x < n; x++) {

      for (b = 0; b < 8; b++) {
        i = x * 8 + b;

        if (result[y * n + x] === undefined) {
          result[y * n + x] = 0;
        }

        c = x * 8 + b;
        if (c < width) {
          if (data[y * width + i]) {
            result[y * n + x] += (0x80 >> (b & 0x7));
          }
        }
      }
    }
  }
  return {
    data: result,
    width: n,
    height: height
  };
}

/**
 * [exports description]
 * @type {[type]}
 */
module.exports = Image;