如何提高jsPDF下载的pdf文件的像素/分辨率

Below code of jsPDF is working fine but when it downloads the pdf file the resolution/pixels are very poor images and text is blur.

How can we increase the pixels/resolutions of the jsPDF downloaded file.

function completedsx_<?php echo $ohhz['order_id']; ?>() {

var pdf = new jsPDF('p', 'pt', 'a4');
pdf.addHTML($("#content<?php echo $ohhz['order_id']; ?>")[0], function() {
pdf.save('Invoice_<?php echo $ohhz['order_id']; ?>.pdf');
});
}