Pdf file size too big created using jspdf

问题:

I am using jspdf for creating PDF inside browser. I am having multiple charts having svg as chart Data. For adding data to pdf I am converting svg to png using canvas and then Base64 Data using canvas.toDataURL method. After all this conversions size of the file created by jspdf is huge (about 50 MB). Below is the code for div of chart data and canvas.

newdiv = document.createElement("div");
newdiv.className = "big_Con_graph big_Con_graph0";
newdiv.style.height = "0px";
newdiv.id = "big_Con_graph" + id;

below is the dimensions for SVG chart load.

document.getElementById("big_Con_graph" + id).style.display = "block";
var big_chartReference = FusionCharts("big_myChartId"+id);
if(big_chartReference != null){
    big_chartReference.dispose();
}
var big_width = "1088";
var big_height = "604";

now below is the code for conversion of above graph SVG data and adding to PDF.

var elem_graph = $($('.big_Con_graph,big_Con_graph0')[count]).clone(true);
svgString = $(elem_graph).find("span").html();
var img = document.createElement('img');
var DOMURL = self.URL || self.webkitURL || self;
var svg = new Blob([svgString], {type: "image/svg+xml;charset=utf-8"});
var url = DOMURL.createObjectURL(svg);
img.onload = pdfAfterImageLoad(img,pdf,imgLoadSequence,DOMURL,totalReports,reportName);
img.src = url;

this is the code for PDFAfterImageLoad function:

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
var png = canvas.toDataURL("image/png");
pdf.addImage(png, 'PNG', leftmargin, 120, 485, 270);

I am using png, so imagequality parameter can not be used.

Can anyone help me decrease the file size?

回答1:

You need to compress the images in the PDF's that you are generating. Try using Deflate.js and adler32cs.js and use the compress parameter in both jsPDF and addImage functions that you are using. For eg :

var doc = new jsPDF('p', 'pt','a4',true);

make sure you set the last parameter as 'true' refer to : https://github.com/MrRio/jsPDF/blob/ddbfc0f0250ca908f8061a72fa057116b7613e78/jspdf.js#L146

Go through it and you can clearly see that the last parameter is for enabling compression.

Also use :

pdf.addImage(png, 'PNG', leftmargin, 120, 485, 270,'','FAST');

instead of

pdf.addImage(png, 'PNG', leftmargin, 120, 485, 270);

you can choose between NONE, FAST, MEDIUM and SLOW, whichever suits you best.

回答2:

If you add several images to one document, use

pdf.addImage(png, 'PNG', leftmargin, 120, 485, 270, undefined,'FAST');

not

pdf.addImage(png, 'PNG', leftmargin, 120, 485, 270,'','FAST');

otherwise the first image will substitute all others.

回答3:

Have you tried canvg? It's not very likely that it will decrease the filesize, but at least you can try.

See a snippet in this reply.

回答4:

In my case did not work with compress parameter. So, I resized the current image on my own with the following function:

function resizeBase64Img(base64, width, height) {
    var canvas = document.createElement("canvas");
    canvas.width = width;
    canvas.height = height;
    var context = canvas.getContext("2d");
    var deferred = $.Deferred();
    $("<img/>").attr("src", "data:image/gif;base64," + base64).load(function() {
        context.scale(width/this.width,  height/this.height);
        context.drawImage(this, 0, 0); 
        deferred.resolve($("<img/>").attr("src", canvas.toDataURL()));               
    });
    return deferred.promise();    
}

And call it as follows:

//select my image in base64
var imageStr64 = "/9j/4RiDRXhpZgAATU0AKgA...";
//resize image, add image and create the pdf
resizeBase64Img(imageStr64, 1000, 1000).then(function(newImg){
    doc.addImage($(newImg).attr('src'), 15, 90, 180,180);
    doc.save('mypdf.pdf');
});

You can play with 'width' and 'height' parameters in resizeBase64Img function in order to generate heavy pdf with better or worst image quality.