HTML5 canvas, convert canvas to PDF with jspdf.js

Question

I am trying to convert HTML5 canvas to PDF in JavaScript but I get a black background PDF. I tried to change the background color but still get black. The following is code I am

Answer 1

I had the same problem, e.g. the first time when i create a pdf the canvas image is ok, but all the other next, came out black. No picture!

The workaround i found is as follows: after each call to pdf.addImage() i redraw the picture in the canvas. It works now fine for me.

EDIT: As requested, here some more details:

Let say i have a canvas drawing function like this (just an example, it doesn't matter):

function drawCanvas(cv) {
  for(var i=0; i

I had to fix my printing function as follows:

var cv=document.getElementById('canvas');
printPDF(cv) {
    var imgData=cv.toDataURL("image/jpeg", 1.0);
    var doc=new jsPDF("p","mm","a4");
    doc.addImage(imgData,'JPEG',15,40,180,180);
    drawCanvas(cv); // <--- this line is needed, draw again
}
drawCanvas(cv); // <--- draw my image to the canvas, ok
printPDF(cv); // first time is fine
printPDF(cv); // second time without repaint would be black

I admit, i did'nt investigate further, just happy that this works.