49 lines
1.6 KiB
JavaScript
49 lines
1.6 KiB
JavaScript
// Web Worker wrapper for image resize function
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'use strict';
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module.exports = function () {
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const MathLib = require('./mathlib');
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let mathLib;
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/* eslint-disable no-undef */
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onmessage = function (ev) {
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let tileOpts = ev.data.opts;
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let returnBitmap = false;
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if (!tileOpts.src && tileOpts.srcBitmap) {
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let canvas = new OffscreenCanvas(tileOpts.width, tileOpts.height);
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let ctx = canvas.getContext('2d', { alpha: Boolean(tileOpts.alpha) });
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ctx.drawImage(tileOpts.srcBitmap, 0, 0);
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tileOpts.src = ctx.getImageData(0, 0, tileOpts.width, tileOpts.height).data;
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canvas.width = canvas.height = 0;
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canvas = null;
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tileOpts.srcBitmap.close();
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tileOpts.srcBitmap = null;
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// Temporary force out data to typed array, because Chrome have artefacts
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// https://github.com/nodeca/pica/issues/223
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// returnBitmap = true;
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}
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if (!mathLib) mathLib = new MathLib(ev.data.features);
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// Use multimath's sync auto-init. Avoid Promise use in old browsers,
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// because polyfills are not propagated to webworker.
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let data = mathLib.resizeAndUnsharp(tileOpts);
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if (returnBitmap) {
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let toImageData = new ImageData(new Uint8ClampedArray(data), tileOpts.toWidth, tileOpts.toHeight);
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let canvas = new OffscreenCanvas(tileOpts.toWidth, tileOpts.toHeight);
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let ctx = canvas.getContext('2d', { alpha: Boolean(tileOpts.alpha) });
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ctx.putImageData(toImageData, 0, 0);
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createImageBitmap(canvas).then(bitmap => {
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postMessage({ bitmap }, [ bitmap ]);
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});
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} else {
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postMessage({ data }, [ data.buffer ]);
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}
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};
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};
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