Is it Possible to add jpg BASE64-strings to a PDF Base64-string?

[pwinkelm]

Hello,

hopefully you can help me out on this. I have a certain service which gives me a base64 pdf string and 0-n base64 jpg strings.

Is it possible to append the base64 images to the base64 pdf using hummusJS?

Thanks for your answer!

[chunyenHuang]

#74 #77 #82

[pwinkelm]

@chunyenHuang thanks you for your reply but I really mean: I got a pdf as a base64-string and several images as base64-string. In what way can I append the images to the pdf with (I am using node) using the base64-stream module for nodejs. I do see very little explanation on how to use the Streams with hummusJs. May be you have some small code examples? I am very new to this and would love to get some more help! Really appreciated. Thank you!

[pwinkelm]

I forgot to mention: I donot want to write the file to the filesystem (= on the server) first and then create a stream. Kind regards, Pieter

[richard-kurtosys]

For the pdf you would need to change your base64 PDF string to a buffer and then use:

    const streams = require('memory-streams');
    
	// pdf_buffer would be your base64 pdf string as a buffer
    const inStream = new PDFRStreamForBuffer(pdf_buffer); //PDFRStreamForBuffer is here: https://github.com/galkahana/HummusJS/pull/202/files
    const ws = new streams.WritableStream();
    const outStream = new hummus.PDFStreamForResponse(ws);
    const pdfWriter = hummus.createWriterToModify(inStream, outStream, );
    // Now do stuff to the PDF as you normally would or as you see in all the examples
    // once done:
    pdfWriter.end();
    return ws;

Once you've finished doing stuff to your PDF then ws should contain your output buffer. If you're in node then you should be able to do:

// const pdf = convertFromBase64ToBuffer(pdfBase64String); 
const modifiedPDF = doPDFModification(pdf);  //This function would have the code snippet above and do the pdf modification. modifiedPDF contains the returned ws from above.
res.attachment(result.filename);
res.send(modifiedPDF.toBuffer()).end();

[pwinkelm]

Thank you @richard-kurtosys, I will give it a try!

[pwinkelm]

@richard-kurtosys, all working until the pdfWriter. It is not created. Not knowing what is wrong there. Not logging: "after pdfWriter"

My code: ` var pdfBuffer = self.convertFromBase64ToBuffer(pdfBase64String); var inStream = new PDFRStreamForBuffer(pdfBuffer);

			var ws = new memoryStreams.WritableStream();
			console.log("ws: " + JSON.stringify(ws));
		    var outStream = new hummus.PDFStreamForResponse(ws);

		    // create the writer...not working.
		    var pdfWriter = hummus.createWriterToModify(inStream, outStream);
			console.log("after pdfWriter");

`

[pwinkelm]

Managed to get the errormessage: "Unable to modify PDF file, make sure that output file target is available and that it is not protected"

[richard-kurtosys]

I'm not too sure what the issue could be there as it's definitely working for me.

You can try make your output go direct to a file, just to see that it does work correctly. If it does then you know the issue is definitely with the stream and not something else:

var pdfWriter = hummus.createWriterToModify(inStream, './output.pdf');
console.log("after pdfWriter");

You should now have a output.pdf file somewhere with your output in it.

My package.json entry for memory-streams is: "memory-streams": "^0.1.3" (maybe this helps?)

[richard-kurtosys]

I've just had to convert a readStream to a buffer and then use that as an input, it looks like:

const pdfAsBuffer = await resolveReadStream(result.readStream);
const watermarked = watermarkDocument(pdfAsBuffer);
res.attachment("output.pdf");
res.send(watermarked.toBuffer()).end();

and then watermarkDocument has:

export function watermarkDocument(document) {
    const inStream = new PDFRStreamForBuffer(document);
    const readStream = new PDFRStreamForBuffer(document);
    const ws = new streams.WritableStream();
    const outStream = new hummus.PDFStreamForResponse(ws);
    const pdfWriter = hummus.createWriterToModify(inStream, outStream );
	....
	....
	pdfWriter.end();
    return ws;
}

[pwinkelm]

Thank you again @richard-kurtosys. I am using ^0.1.3 for the memory-streams. Will have a look in coming days. Now focussing on another client! Will come back on it.

[taozhiyuzhuo]

Managed to get the errormessage: "Unable to modify PDF file, make sure that output file target is available and that it is not protected"

Hi, i have the same probleme, do you solve it?

[wisefin-yu]

This works well

  const writeStream = new hummus.PDFStreamForResponse(res);
  const pdfBuffer = new Buffer.from(base64string, 'base64');
  const readStream = new hummus.PDFRStreamForBuffer(pdfBuffer);
  const pdfWriter = hummus.createWriterToModify(readStream, writeStream, {
    log: 'log.txt',
  });
  const pageModifier = new hummus.PDFPageModifier(pdfWriter, 0, true);
  const doc = pageModifier.startContext().getContext();
  doc.writeText('test'), 0, 200);
  pageModifier.endContext().writePage();
  pdfWriter.end();