Working with PDF File Metadata using JavaScript via C++

Get PDF File Information

  1. Create a ‘FileReader’.
  2. The AsposePdfGetInfo function is executed.
  3. PDF metadata that can be obtained:
  • title - title
  • creator - creator
  • author - author
  • subject - subject
  • keywords - keywords
  • creation - creation date
  • mod - modify date
  1. Next, if the ‘json.errorCode’ is 0, then you can get list of PDF file Info. If the ‘json.errorCode’ parameter is not equal to 0 and, accordingly, there will be an error in your file, then information about such an error will be contained in the ‘json.errorText’ file.

  var ffilePdfGetInfo = function (e) {
    const file_reader = new FileReader();
    file_reader.onload = (event) => {
      /*Get info (metadata) from PDF file.*/
      const json = AsposePdfGetInfo(event.target.result, e.target.files[0].name);
      /* JSON
      title - title
      creator - creator
      author - author
      subject - subject
      keywords - keywords
      format - PDF format
      version - PDF version
      ispdfa - PDF is PDF/A
      ispdfua - PDF is PDF/UA
      islinearized - PDF is linearized
      isencrypted - PDF is encrypted
      permission - PDF permission
      size - PDF page size
      pagecount - Page count
      сreation Date: json.creation
      modify Date:   json.mod
      annotationcount - Annotation count
      bookmarkcount - Bookmark count
      attachmentcount - Attachment count
      metadatacount - Metadata count
      javascriptcount - JavaScript count
      imagecount - Image count
      */
      if (json.errorCode == 0) document.getElementById('output').textContent = "JSON:\n" + JSON.stringify(json, null, 4);
      else document.getElementById('output').textContent = json.errorText;
    };
    file_reader.readAsArrayBuffer(e.target.files[0]);
  };

Using Web Workers


    /*Create Web Worker*/
    const AsposePDFWebWorker = new Worker("AsposePDFforJS.js");
    AsposePDFWebWorker.onerror = evt => console.log(`Error from Web Worker: ${evt.message}`);
    AsposePDFWebWorker.onmessage = evt => document.getElementById('output').textContent = 
      (evt.data == 'ready') ? 'loaded!' :
        (evt.data.json.errorCode == 0) ?
          `info:\n${JSON.stringify(evt.data.json, null, 4)}` :
          `Error: ${evt.data.json.errorText}`; 

    /*Event handler*/
    const ffilePdfGetInfo = e => {
      const file_reader = new FileReader();
      file_reader.onload = event => {
        /*Get info (metadata) from a PDF-file - Ask Web Worker*/
        AsposePDFWebWorker.postMessage(
          { "operation": 'AsposePdfGetInfo', "params": [event.target.result, e.target.files[0].name] },
          [event.target.result]
        );
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };

Get All Fonts

Getting fonts from a PDF file can be a useful way to reuse fonts in other documents or applications.

In case you want to get all fonts from a PDF document, you can use AsposePdfGetAllFonts. Please check following code snippet in order to get all fonts from an existing PDF document using JavaScript via C++.

  1. Create a ‘FileReader’.
  2. The AsposePdfGetAllFonts function is executed.
  3. Next, if the ‘json.errorCode’ is 0, then you can get list of fonts from PDF file. If the ‘json.errorCode’ parameter is not equal to 0 and, accordingly, there will be an error in your file, then information about such an error will be contained in the ‘json.errorText’ file.

  var ffilePdfGetAllFonts = function (e) {
    const file_reader = new FileReader();
    file_reader.onload = (event) => {
      /*get list of fonts from PDF file.*/
      const json = AsposePdfGetAllFonts(event.target.result, e.target.files[0].name);
      if (json.errorCode == 0) document.getElementById('output').textContent = "JSON:\n" + JSON.stringify(json, null, 4);
      else document.getElementById('output').textContent = json.errorText;
    };
    file_reader.readAsArrayBuffer(e.target.files[0]);
  };

Using Web Workers


    /*Create Web Worker*/
    const AsposePDFWebWorker = new Worker("AsposePDFforJS.js");
    AsposePDFWebWorker.onerror = evt => console.log(`Error from Web Worker: ${evt.message}`);
    AsposePDFWebWorker.onmessage = evt => document.getElementById('output').textContent = 
      (evt.data == 'ready') ? 'loaded!' :
        (evt.data.json.errorCode == 0) ?
          `fonts:\n${JSON.stringify(evt.data.json.fonts, null, 4)}` :
          `Error: ${evt.data.json.errorText}`; 

    /*Event handler*/
    const ffilePdfGetAllFonts = e => {
      const file_reader = new FileReader();
      file_reader.onload = event => {
        /*Get list fonts a PDF-file - Ask Web Worker*/
        AsposePDFWebWorker.postMessage(
          { "operation": 'AsposePdfGetAllFonts', "params": [event.target.result, e.target.files[0].name] },
          [event.target.result]
        );
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };

Set PDF File Information

Aspose.PDF for JavaScript via C++ allows you to set file-specific information for a PDF, information like author, creation date, subject, and title. To set this information:

  1. Create a ‘FileReader’.
  2. If not need to set value, use undefined or "" (empty string).
  3. The AsposePdfSetInfo function is executed.
  4. The name of the resulting file is set, in this example “ResultSetInfo.pdf”.
  5. Next, if the ‘json.errorCode’ is 0, then your DownloadFile is given the name you specified earlier. If the ‘json.errorCode’ parameter is not equal to 0 and, accordingly, there will be an error in your file, then information about such an error will be contained in the ‘json.errorText’ file.
  6. As a result, the DownloadFile function generates a link and allows you to download the resulting file to the user’s operating system.

    var ffilePdfSetInfo = function (e) {
      const file_reader = new FileReader();
      file_reader.onload = (event) => {
        /*Set PDF info: title, creator, author, subject, keywords, creation (date), mod (date modify)*/
        /*If not need to set value, use undefined or "" (empty string)*/
        /*Set info (metadata) in a PDF-file and save the "ResultSetInfo.pdf"*/
        const json = AsposePdfSetInfo(event.target.result, e.target.files[0].name, "Setting PDF Document Information", "", "Aspose", undefined, "Aspose.Pdf, DOM, API", undefined, "16/02/2023 11:55 PM", "ResultSetInfo.pdf");
        if (json.errorCode == 0) document.getElementById('output').textContent = json.fileNameResult;
        else document.getElementById('output').textContent = json.errorText;
        /*Make a link to download the result file*/
        DownloadFile(json.fileNameResult, "application/pdf");
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };

Using Web Workers


    /*Create Web Worker*/
    const AsposePDFWebWorker = new Worker("AsposePDFforJS.js");
    AsposePDFWebWorker.onerror = evt => console.log(`Error from Web Worker: ${evt.message}`);
    AsposePDFWebWorker.onmessage = evt => document.getElementById('output').textContent = 
      (evt.data == 'ready') ? 'loaded!' :
        (evt.data.json.errorCode == 0) ?
          `Result:\n${DownloadFile(evt.data.json.fileNameResult, "application/pdf", evt.data.params[0])}` :
          `Error: ${evt.data.json.errorText}`;

    /*Event handler*/
    const ffilePdfSetInfo = e => {
      const file_reader = new FileReader();
      file_reader.onload = event => {
        /*PDF info: title, creator, author, subject, keywords, creation (date), mod (date modify)*/
        const title = 'Setting PDF Document Information';
        const creator = ''; /*if not need to set value, use: undefined or ""/'' (empty string)*/
        const author = 'Aspose';
        const subject = undefined;
        const keywords = 'Aspose.Pdf, DOM, API';
        const creation = undefined; /*create date*/
        const mod = '16/02/2023 11:55 PM'; /*modify date*/
        /*Set info (metadata) in a PDF-file and save the "ResultSetInfo.pdf" - Ask Web Worker*/
        AsposePDFWebWorker.postMessage(
          { "operation": 'AsposePdfSetInfo',
            "params": [event.target.result, e.target.files[0].name, title, creator, author, subject, keywords, creation, mod, "ResultSetInfo.pdf"] },
          [event.target.result]
        );
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };

    /*Make a link to download the result file*/
    const DownloadFile = (filename, mime, content) => {
        mime = mime || "application/octet-stream";
        var link = document.createElement("a"); 
        link.href = URL.createObjectURL(new Blob([content], {type: mime}));
        link.download = filename;
        link.innerHTML = "Click here to download the file " + filename;
        document.body.appendChild(link); 
        document.body.appendChild(document.createElement("br"));
        return filename;
      }

Remove PDF File Information

Aspose.PDF for JavaScript via C++ allows you to remove PDF file Metadata:

  1. Create a ‘FileReader’.
  2. The AsposePdfRemoveMetadata function is executed.
  3. The name of the resulting file is set, in this example “ResultPdfRemoveMetadata.pdf”.
  4. Next, if the ‘json.errorCode’ is 0, then your DownloadFile is given the name you specified earlier. If the ‘json.errorCode’ parameter is not equal to 0 and, accordingly, there will be an error in your file, then information about such an error will be contained in the ‘json.errorText’ file.
  5. As a result, the DownloadFile function generates a link and allows you to download the resulting file to the user’s operating system.

    var ffilePdfRemoveMetadata = function (e) {
      const file_reader = new FileReader();
      file_reader.onload = (event) => {
        /*Remove metadata a PDF-file and save the "ResultPdfRemoveMetadata.pdf"*/
        const json = AsposePdfRemoveMetadata(event.target.result, e.target.files[0].name, "ResultPdfRemoveMetadata.pdf");
        if (json.errorCode == 0) document.getElementById('output').textContent = json.fileNameResult;
        else document.getElementById('output').textContent = json.errorText;
        /*Make a link to download the result file*/
        DownloadFile(json.fileNameResult, "application/pdf");
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };

Using Web Workers


    /*Create Web Worker*/
    const AsposePDFWebWorker = new Worker("AsposePDFforJS.js");
    AsposePDFWebWorker.onerror = evt => console.log(`Error from Web Worker: ${evt.message}`);
    AsposePDFWebWorker.onmessage = evt => document.getElementById('output').textContent = 
      (evt.data == 'ready') ? 'loaded!' :
        (evt.data.json.errorCode == 0) ? `Result:\n${DownloadFile(evt.data.json.fileNameResult, "application/pdf", evt.data.params[0])}` : `Error: ${evt.data.json.errorText}`;

    /*Event handler*/
    const ffilePdfRemoveMetadata = e => {
      const file_reader = new FileReader();
      file_reader.onload = event => {
        /*Remove metadata a PDF-file and save the "ResultPdfRemoveMetadata.pdf" - Ask Web Worker*/
        AsposePDFWebWorker.postMessage({ "operation": 'AsposePdfRemoveMetadata', "params": [event.target.result, e.target.files[0].name, "ResultPdfRemoveMetadata.pdf"] }, [event.target.result]);
      };
      file_reader.readAsArrayBuffer(e.target.files[0]);
    };
  /// [Code snippet]

    /*Make a link to download the result file*/
    const DownloadFile = (filename, mime, content) => {
        mime = mime || "application/octet-stream";
        var link = document.createElement("a"); 
        link.href = URL.createObjectURL(new Blob([content], {type: mime}));
        link.download = filename;
        link.innerHTML = "Click here to download the file " + filename;
        document.body.appendChild(link); 
        document.body.appendChild(document.createElement("br"));
        return filename;
      }
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