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Nodejs / Guides / Extract layer

Extract layers from PDF in Node.js

To extract PDF layers or OCG (optional content group) from a document.

async function main() {
    const doc = await PDFNet.PDFDoc.createFromURL(filename);
    const page = await doc.getPage(1);

    const initCfg = await doc.getOCGConfig();
    const ctx = await PDFNet.OCGContext.createFromConfig(initCfg);

    const pdfdraw = await PDFNet.PDFDraw.create();
    pdfdraw.setImageSize(1000, 1000);

    // Disable drawing of content that is not optional (i.e. is not part of any layer).

    // Now render each layer in the input document to a separate image.
    const ocgs = await doc.getOCGs(); // Get the array of all OCGs in the document.
    let i;
    const sz = await ocgs.size();
    for (i = 0; i < sz; ++i) {
        const ocg = await PDFNet.OCG.createFromObj(await ocgs.getAt(i));
        ctx.setState(ocg, true);
        let fname = 'pdf_layers_';
        fname += await ocg.getName();
        fname += '.png';
        const pageBuffer = await pdfdraw.exportStream(page);
        const imageData = new Blob([pageBuffer], {type: 'image/png'}));

    // Now draw content that is not part of any layer...
    const nonLayerBuffer = await pdfdraw.exportStream(page);
    const data = new Blob([nonLayerBuffer], {type: 'image/png'}));

PDF layers (OCG)
Full sample code which demonstrates how to create, extract, render PDF layers.

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