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Reuse rotate instance and calculate pages correctly

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This commit is contained in:
Surma
2019-02-11 16:14:37 +00:00
parent b6a8f7eeba
commit ef3faa58bc
1 changed files with 13 additions and 6 deletions
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19
src/codecs/rotate/processor.ts
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@@ -1,23 +1,30 @@
import wasmUrl from '../../../codecs/rotate/rotate.wasm';
import { RotateOptions, RotateModuleInstance } from './processor-meta';
const instancePromise = (WebAssembly as any).instantiateStreaming(fetch(wasmUrl));
export async function rotate(
data: ImageData,
opts: RotateOptions,
): Promise<ImageData> {
const flipDimensions = opts.rotate % 180 !== 0;
const { instance } = (await instancePromise) as {instance: 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 / (64 * 1024));
const { instance } = (await (WebAssembly as any).instantiateStreaming(
fetch(wasmUrl),
)) as { instance: RotateModuleInstance };
const numPagesNeeded = Math.ceil(bytesPerImage * 2 / (64 * 1024) + 4);
// Only count full pages, just to be safe.
const numPagesAvailable = Math.floor(instance.exports.memory.buffer.byteLength / (64 * 1024));
const additionalPagesToAllocate = numPagesNeeded - numPagesAvailable;
instance.exports.memory.grow(numPagesNeeded);
if (additionalPagesToAllocate > 0) {
instance.exports.memory.grow(additionalPagesToAllocate);
}
const view = new Uint8ClampedArray(instance.exports.memory.buffer);
view.set(data.data);
instance.exports.rotate(data.width, data.height, opts.rotate);
const flipDimensions = opts.rotate % 180 !== 0;
return new ImageData(
view.slice(bytesPerImage, bytesPerImage * 2),
flipDimensions ? data.height : data.width,