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41 lines
1.4 KiB
41 lines
1.4 KiB
import BaseDecoder from './basedecoder.js';
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/**
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* class WebImageDecoder
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*
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* This decoder uses the browsers image decoding facilities to read image
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* formats like WebP when supported.
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*/
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export default class WebImageDecoder extends BaseDecoder {
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constructor() {
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super();
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if (typeof createImageBitmap === 'undefined') {
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throw new Error('Cannot decode WebImage as `createImageBitmap` is not available');
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} else if (typeof document === 'undefined' && typeof OffscreenCanvas === 'undefined') {
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throw new Error('Cannot decode WebImage as neither `document` nor `OffscreenCanvas` is not available');
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}
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}
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async decode(fileDirectory, buffer) {
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const blob = new Blob([buffer]);
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const imageBitmap = await createImageBitmap(blob);
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let canvas;
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if (typeof document !== 'undefined') {
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canvas = document.createElement('canvas');
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canvas.width = imageBitmap.width;
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canvas.height = imageBitmap.height;
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} else {
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canvas = new OffscreenCanvas(imageBitmap.width, imageBitmap.height);
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}
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const ctx = canvas.getContext('2d');
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ctx.drawImage(imageBitmap, 0, 0);
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// TODO: check how many samples per pixel we have, and return RGB/RGBA accordingly
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// it seems like GDAL always encodes via RGBA which does not require a translation
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return ctx.getImageData(0, 0, imageBitmap.width, imageBitmap.height).data.buffer;
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}
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}
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