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61 lines
2.3 KiB
TypeScript
61 lines
2.3 KiB
TypeScript
/**
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* Copyright 2020 Google Inc. All Rights Reserved.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import wasmUrl from 'url:codecs/rotate/rotate.wasm';
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import { Options } from '../shared/meta';
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export interface RotateModuleInstance {
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exports: {
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memory: WebAssembly.Memory;
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rotate(width: number, height: number, rotate: 0 | 90 | 180 | 270): void;
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};
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}
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// We are loading a 500B module here. Loading the code to feature-detect
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// `instantiateStreaming` probably takes longer to load than the time we save by
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// using `instantiateStreaming` in the first place. So let’s just use
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// `ArrayBuffer`s here.
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const instancePromise = fetch(wasmUrl)
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.then((r) => r.arrayBuffer())
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.then((buf) => WebAssembly.instantiate(buf));
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export default async function rotate(
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data: ImageData,
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opts: Options,
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): Promise<ImageData> {
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const instance = (await instancePromise).instance as RotateModuleInstance;
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// Number of wasm memory pages (á 64KiB) needed to store the image twice.
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const bytesPerImage = data.width * data.height * 4;
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const numPagesNeeded = Math.ceil((bytesPerImage * 2 + 8) / (64 * 1024));
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// Only count full pages, just to be safe.
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const numPagesAvailable = Math.floor(
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instance.exports.memory.buffer.byteLength / (64 * 1024),
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);
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const additionalPagesToAllocate = numPagesNeeded - numPagesAvailable;
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if (additionalPagesToAllocate > 0) {
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instance.exports.memory.grow(additionalPagesToAllocate);
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}
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const view = new Uint8ClampedArray(instance.exports.memory.buffer);
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view.set(data.data, 8);
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instance.exports.rotate(data.width, data.height, opts.rotate);
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const flipDimensions = opts.rotate % 180 !== 0;
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return new ImageData(
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view.slice(bytesPerImage + 8, bytesPerImage * 2 + 8),
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flipDimensions ? data.height : data.width,
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flipDimensions ? data.width : data.height,
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);
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}
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