fastman3-dfyjapp-jsbridge/es/resizeBase64.js

a jsbridge module for dfyj app

function _processBase64(img, maxWidth, maxHeight, callback) {
  // Max size for thumbnail
  if (typeof maxWidth === 'undefined') maxWidth = 500;
  if (typeof maxHeight === 'undefined') maxHeight = 500;

  // Create and initialize two canvas
  var canvas = document.createElement("canvas");
  var ctx = canvas.getContext("2d");
  var canvasCopy = document.createElement("canvas");
  var copyContext = canvasCopy.getContext("2d");

  // // Create original image
  // var img = new Image();
  // img.src = base64;

  // Determine new ratio based on max size
  var ratio = 1;
  if (img.width > maxWidth) ratio = maxWidth / img.width;else if (img.height > maxHeight) ratio = maxHeight / img.height;

  // Draw original image in second canvas
  canvasCopy.width = img.width;
  canvasCopy.height = img.height;
  copyContext.drawImage(img, 0, 0);

  // Copy and resize second canvas to first canvas
  canvas.width = img.width * ratio;
  canvas.height = img.height * ratio;
  ctx.drawImage(canvasCopy, 0, 0, canvasCopy.width, canvasCopy.height, 0, 0, canvas.width, canvas.height);
  var resizeDataURL = canvas.toDataURL();
  if (typeof callback == "function") {
    callback(resizeDataURL);
  }
}
function _loadImage(imgSrc, maxWidth, maxHeight, callback) {
  // Create original image
  var image = new Image();
  image.src = imgSrc;
  if (image.complete) {
    _processBase64(image, maxWidth, maxHeight, callback);
    image.onload = function () {};
  } else {
    image.onload = function () {
      _processBase64(image, maxWidth, maxHeight, callback);
      // clear onLoad, IE behaves erratically with animated gifs otherwise
      image.onload = function () {};
    };
    image.onerror = function () {
      alert("Could not load image.");
    };
  }
}

/**
 * 将base64转换为规定的尺寸
 * @param {*} base64 DataURI
 * @param {*} maxWidth 最大宽度
 * @param {*} maxHeight 最大高度
 * @param {*} callback 异步回调
 */
function asyncResizeBase64(base64, maxWidth, maxHeight, callback) {
  _loadImage(base64, maxWidth, maxHeight, callback);
}
export { asyncResizeBase64 };