44 lines
1.6 KiB
TypeScript
44 lines
1.6 KiB
TypeScript
import wasmUrl from '../../../codecs/rotate/rotate.wasm';
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import { RotateOptions, RotateModuleInstance } from './processor-meta';
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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 async function rotate(
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data: ImageData,
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opts: RotateOptions,
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): Promise<ImageData> {
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const { instance } = (await instancePromise) as {
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instance: RotateModuleInstance;
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};
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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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