67 lines
2.7 KiB
JavaScript
67 lines
2.7 KiB
JavaScript
"use strict";
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var __importDefault = (this && this.__importDefault) || function (mod) {
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return (mod && mod.__esModule) ? mod : { "default": mod };
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};
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Object.defineProperty(exports, "__esModule", { value: true });
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const basedecoder_js_1 = __importDefault(require("./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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class WebImageDecoder extends basedecoder_js_1.default {
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/**
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* @param {import('./basedecoder.js').BaseDecoderParameters} parameters
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*/
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constructor(parameters) {
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super(parameters);
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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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}
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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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/** @param {ArrayBuffer} buffer */
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async decodeBlock(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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}
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else {
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canvas = new OffscreenCanvas(imageBitmap.width, imageBitmap.height);
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}
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// Draw the image onto the canvas to extract the pixel data.
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// Note: createImageBitmap always returns RGBA data.
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const ctx = /** @type {CanvasRenderingContext2D} */ (canvas.getContext('2d'));
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ctx.drawImage(imageBitmap, 0, 0);
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const imageData = ctx.getImageData(0, 0, imageBitmap.width, imageBitmap.height).data;
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// Return the correct channels to the caller
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const samplesPerPixel = this.parameters.samplesPerPixel || 4;
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if (samplesPerPixel === 4) {
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// RGBA, return as is
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return imageData.buffer;
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}
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else if (samplesPerPixel === 3) {
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// RGB, remove alpha channel before returning
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const rgb = new Uint8ClampedArray(imageBitmap.width * imageBitmap.height * 3);
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for (let i = 0, j = 0; i < rgb.length; i += 3, j += 4) {
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rgb[i] = imageData[j];
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rgb[i + 1] = imageData[j + 1];
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rgb[i + 2] = imageData[j + 2];
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}
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return rgb.buffer;
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}
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else {
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throw new Error(`Unsupported SamplesPerPixel value: ${samplesPerPixel}`);
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}
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}
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}
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exports.default = WebImageDecoder;
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//# sourceMappingURL=webimage.js.map
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//# sourceMappingURL=webimage.js.map
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