lenye_base/image_optimization.js

基础方法

'use strict';

require('./get_tag.js');
var is_string = require('./is_string.js');

/**
 * Image optimization
 * Gif images are not supported
 * @param {(Object|String)} - image ,supported File Object or Data URLs
 * @param {Number} [quality = 0.9] - Image quality, between 0 - 1, only image/jpeg or image/webp is accept.
 * @param {Object} [options = {}] - Image options
 * @param {Number} [options.maxWidth = 1920] - The maximum width of the output picture.
 * If the original width of the picture is less than this width, the original size picture is returned.
 * If the original width of the picture is greater than the width, the picture scaled to the size is returned.
 * @param {String} [options.mimeType] - Output image type，Types of MIME.
 * @returns {Object} Promise , resolve Function parameters are optimized pictures Blob Object,
 * If the output type is image/gif，Then return as is image Parameter content.
 */

var imageOptimization = function (image) {
  var quality = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0.9;

  var _ref = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {},
      _ref$maxWidth = _ref.maxWidth,
      maxWidth = _ref$maxWidth === void 0 ? 1920 : _ref$maxWidth,
      mimeType = _ref.mimeType;

  return new Promise((resolve, reject) => {
    if (image instanceof File) {
      var reader = new FileReader();

      reader.onload = function () {
        toBlob(this.result);
      };

      reader.readAsDataURL(image);
    } else if (is_string(image)) {
      toBlob(image);
    }
    /**
     * To Blob
     * @param {String} data - Image: Data URL
     */


    function toBlob(data) {
      var type = data.match(/data:([^;,]+)/);

      if (Array.isArray(type)) {
        var outputType = mimeType ? mimeType : type[1];

        if (outputType === 'image/gif') {
          return resolve(image);
        }

        var virtualImage = new Image();
        virtualImage.src = data;

        virtualImage.onload = function () {
          var width = this.naturalWidth;
          var height = this.naturalHeight;

          if (width > maxWidth) {
            height = Math.round(maxWidth * height / width);
            width = maxWidth;
          }

          var canvas = document.createElement('canvas');
          canvas.width = width;
          canvas.height = height;
          var context = canvas.getContext('2d');
          context.drawImage(this, 0, 0, width, height);
          canvas.toBlob(blob => {
            resolve(blob);
          }, mimeType ? mimeType : type[1], quality);
        };
      } else {
        reject(new Error('Non-picture type Data URLs'));
      }
    }
  });
};

module.exports = imageOptimization;