image-js/lib/stack/load/decodeApng.js

Image processing and manipulation in JavaScript

import { decodeApng } from 'fast-png';
import { Image } from "../../Image.js";
import { Stack } from "../../Stack.js";
/**
 * Decodes APNG image into a Stack
 * @param data - APNG data.
 * @returns stack of frames.
 */
export function decodeStackFromApng(data) {
    const decodedApng = decodeApng(data);
    const images = [];
    let colorModel;
    switch (decodedApng.channels) {
        case 1:
            if (decodedApng.palette) {
                colorModel = decodedApng.palette[0].length === 3 ? 'RGB' : 'RGBA';
            }
            else {
                colorModel = 'GREY';
            }
            break;
        case 2:
            colorModel = 'GREYA';
            break;
        case 3:
            colorModel = 'RGB';
            break;
        default:
            colorModel = 'RGBA';
            break;
    }
    if (decodedApng.palette) {
        for (const image of decodedApng.frames) {
            images.push(new Image(decodedApng.width, decodedApng.height, {
                data: convertIndexedData(image.data, decodedApng.palette),
                colorModel,
            }));
        }
    }
    else {
        for (const image of decodedApng.frames) {
            images.push(new Image(decodedApng.width, decodedApng.height, {
                data: image.data,
                colorModel,
            }));
        }
    }
    const stack = new Stack(images);
    return stack;
}
function convertIndexedData(data, palette) {
    const result = new Uint8Array(data.length * palette[0].length);
    for (let i = 0; i < data.length; i++) {
        for (let channel = 0; channel < palette[0].length; channel++) {
            result[i * palette[0].length + channel] = palette[data[i]][channel];
        }
    }
    return result;
}
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