test_util.ts

/**
 * @license
 * Copyright 2019 Google LLC. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * =============================================================================
 */

export async function fetchImage(url: string): Promise<HTMLImageElement> {
  const response = await fetch(url);
  const blob = await response.blob();
  const img = new Image();
  const blobUrl = URL.createObjectURL(blob);
  return new Promise((resolve, reject) => {
    img.onload = () => {
      URL.revokeObjectURL(blobUrl);
      resolve(img);
    };
    img.onerror = (evt /* Arg is an event, not error. Can't rethrow it */) => {
      reject(new Error('Failed to load blob as image.'));
    };
    img.src = blobUrl;
  });
}