Rollup build

src/features/preprocessors/rotate/worker/rotate.ts

@@ -0,0 +1,60 @@
+/**
+ * Copyright 2020 Google Inc. 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.
+ */
+import wasmUrl from 'url:codecs/rotate/rotate.wasm';
+import { Options } from '../shared/meta';
+
+export interface RotateModuleInstance {
+  exports: {
+    memory: WebAssembly.Memory;
+    rotate(width: number, height: number, rotate: 0 | 90 | 180 | 270): void;
+  };
+}
+
+// We are loading a 500B module here. Loading the code to feature-detect
+// `instantiateStreaming` probably takes longer to load than the time we save by
+// using `instantiateStreaming` in the first place. So let’s just use
+// `ArrayBuffer`s here.
+const instancePromise = fetch(wasmUrl)
+  .then((r) => r.arrayBuffer())
+  .then((buf) => WebAssembly.instantiate(buf));
+
+export default async function rotate(
+  data: ImageData,
+  opts: Options,
+): Promise<ImageData> {
+  const instance = (await instancePromise).instance as RotateModuleInstance;
+
+  // Number of wasm memory pages (á 64KiB) needed to store the image twice.
+  const bytesPerImage = data.width * data.height * 4;
+  const numPagesNeeded = Math.ceil((bytesPerImage * 2 + 8) / (64 * 1024));
+  // Only count full pages, just to be safe.
+  const numPagesAvailable = Math.floor(
+    instance.exports.memory.buffer.byteLength / (64 * 1024),
+  );
+  const additionalPagesToAllocate = numPagesNeeded - numPagesAvailable;
+
+  if (additionalPagesToAllocate > 0) {
+    instance.exports.memory.grow(additionalPagesToAllocate);
+  }
+  const view = new Uint8ClampedArray(instance.exports.memory.buffer);
+  view.set(data.data, 8);
+
+  instance.exports.rotate(data.width, data.height, opts.rotate);
+
+  const flipDimensions = opts.rotate % 180 !== 0;
+  return new ImageData(
+    view.slice(bytesPerImage + 8, bytesPerImage * 2 + 8),
+    flipDimensions ? data.height : data.width,
+    flipDimensions ? data.width : data.height,
+  );
+}