downloadIZuKan.js

downloadIZuKan.js

function parse(rawInfo) {
    if (rawInfo.decode_key) {
        rawInfo.decode_key = rawInfo.decode_key.split('-')
    }
    return rawInfo;
}

function decode(info, image, canvas) {
    const d2 = canvas.getContext("2d");
    canvas.width = image.width;
    canvas.height = image.height;

    d2.drawImage(image, 0, 0);
    const {decode_key} = info;
    const width = 96;
    const height = 128;
    const nx = Math.floor(image.width / width);
    // const ny = Math.floor(image.height / height);
    for (let i = 0; i < decode_key.length; i++) {
        const key = decode_key[i];
        const sx = width * Math.floor(i % nx);
        const sy = 128 * Math.floor(i / nx);
        const x = Math.round(96 * Math.floor(key % nx));
        const y = Math.round(128 * Math.floor(key / nx));
        d2.drawImage(image, sx, sy, width, height, x, y, width, height);
    }
}

function makeUrl(page_no) {
    return GUARDIAN_SERVER + "/files/" + FILE_ID + "/images/" + page_no + "/info";
}


const array = [];
let page_no = 0;
const body = document.querySelector('body');

function downloadImg() {
    console.log(`try to download image ${title}_${page_no}.jpg`);
    const toDownload = array[page_no];
    if (toDownload && !toDownload.downloaded) {
        const info = toDownload.info;
        const image = document.createElement('img');
        image.onload = function () {
            console.info(`save image ${title}_${page_no}.jpg`);
            const canvas = document.createElement('canvas');
            decode(info, image, canvas);
            const a = document.createElement('a');
            a.download = title + '_' + page_no + ".jpg";
            canvas.toBlob(blob => {
                a.href = URL.createObjectURL(blob);
                a.click();
                toDownload.downloaded = true;
                image.onload = null;
                body.removeChild(image);
                page_no += 1;
                detect();
            }, "image/jpeg");
        };
        image.src = info.image_url;
        body.appendChild(image)
    }
}

function processInfo(rawInfo) {
    console.info(`downloaded page:${page_no} info`);
    const info = parse(rawInfo);
    array[page_no] = {
        info,
        downloaded: false,
    };
    setTimeout(function () {
        downloadImg();
    }, 200)
}

function reportError() {
    console.error("GET INFO FAILED");
    console.dir(array);
}

function detect(start) {
    if(start){
        page_no =start;
    }
    console.log(`downloading page:${page_no} info`);
    $.ajax({
        url: makeUrl(page_no),
        data: {
            license_id: LICENSE_ID,
            license_token: TOKEN,
        },
        dataType: "jsonp",
        jsonp: "jsoncallback",
        jsonpCallback: "processInfo",
        //success: processInfo,
        error: reportError
    });
}