uTools-quickcommand/plugin/lib/picture-compressor.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = global || self, global.pictureCompress = factory());
}(this, function () { 'use strict';

  /**
   * 将图片压缩为对应尺寸
   * @param {Object} options 
   * @param {String} options.img 图片的url或者base64数据
   * @param {Number} options.width 目标图片的宽度
   * @param {Number} options.height 目标图片的高度
   * @param {Number} options.quality 生成目标图片质量
   * @param {String} options.fit 图片压缩填充模式默认 scale：按比例缩放，可选 fill：按使用目标尺寸
   * @param {String} options.type 图片压缩类型默认 jpg，可选 png
   * @param {Number} options.rotate 图片旋转，由于手机拍照的角度和我们使用的头像不一致，需要旋转 默认0 仅支持 90 180 -90
   * @returns {Promise} then {width,height,img}
   */
  function pictureCompress(options) {
    return new Promise(function (resolve, reject) {
      if (!options.img) {
        reject(new Error('need img'));
        return;
      }

      var imgSrc = options.img,
          width = options.width || 640,
          height = options.height || 640,
          type = options.type || 'jpg',
          quality = options.quality || 0.92,
          fit = options.fit || 'scale',
          rotate = options.rotate || 0;

      if (width <= 0 || height <= 0) {
        reject(new Error('dist width or height need > 0'));
        return;
      }

      if (!/jpg|png|jpeg/.test(type)) {
        reject(new Error('type need jpg or png!'));
        return;
      }

      if (rotate !== 90 && rotate !== -90 && rotate !== 0 && rotate !== 180) {
        reject(new Error('rotate mast be 0 90 -90 180!'));
        return;
      }

      var changeWidthAndHeight = rotate === 90 || rotate === -90;
      var image = new Image();
      image.src = imgSrc;

      image.onload = function () {
        var distSize = getDistSize({
          width: changeWidthAndHeight ? this.naturalHeight : this.naturalWidth,
          height: changeWidthAndHeight ? this.naturalWidth : this.naturalHeight
        }, {
          width: changeWidthAndHeight ? height : width,
          height: changeWidthAndHeight ? width : height
        }, fit);
        var imgData = compress(this, distSize.width, distSize.height, type, quality, rotate);
        resolve({
          width: distSize.width,
          height: distSize.height,
          img: imgData
        });
      };

      image.onerror = function (err) {
        reject(err);
      };
    });
  }
  /**
   * 将图片转换为固定尺寸的
   * @param {Image} img 图片数据
   * @param {Number} width 转换之后的图片宽度
   * @param {Number} height 转换之后的图片高度
   * @param {String} type base64的图片类型 jpg png
   * @param {Number} quality 转换之后的图片质量
   */


  function compress(img, width, height, type, quality, rotate) {
    var canvas = document.createElement('canvas');
    var ctx = canvas.getContext('2d');
    var types = {
      'jpg': 'image/jpeg',
      'jpeg': 'image/jpeg',
      'png': 'image/png'
    };
    canvas.width = width;
    canvas.height = height;

    if (rotate === 90) {
      ctx.translate(width, 0);
      ctx.rotate(90 * Math.PI / 180);
      ctx.drawImage(img, 0, 0, height, width);
    } else if (rotate === -90) {
      ctx.translate(0, height);
      ctx.rotate(-90 * Math.PI / 180);
      ctx.drawImage(img, 0, 0, height, width);
    } else if (rotate === 180) {
      ctx.translate(width, height);
      ctx.rotate(180 * Math.PI / 180);
      ctx.drawImage(img, 0, 0, width, height);
    } else {
      ctx.drawImage(img, 0, 0, width, height);
    }

    return canvas.toDataURL(types[type], quality);
  }
  /**
   * 选择源尺寸与目标尺寸比例中较小的那个，保证图片可以完全显示
   * 最大值不超过1，如果图片源尺寸小于目标尺寸，则不做处理，返回图片原尺寸
   * @param {Object} source 源图片的宽高
   * @param {Object} dist 目标图片的宽高
   */


  function getDistSize(source, dist, fit) {
    if (fit === 'fill') return dist;
    var scale = Math.min(dist.width / source.width, dist.height / source.height, 1);
    return {
      width: Math.round(source.width * scale),
      height: Math.round(source.height * scale)
    };
  }

  return pictureCompress;

}));