Issue in Panning pdf file on canvas which is render with pdf.js?

Question

I am rendering pdf file on canvas with pdf.js. How to Pan pdf on canvas? I am trying out some code for panning but chrome getting crash because of that. Same Code for panning works for image.

Let me know where I am going wrong.

var scale = 1;
 var canvas = document.getElementById('the-canvas');
        var context = canvas.getContext('2d');
function pdfCanvas(scale){

    PDFJS.getDocument('gkhead.pdf').then(function(pdf) {
      // Using promise to fetch the page
      pdf.getPage(1).then(function(page) {
       // var scale = 1.5;
        var viewport = page.getViewport(scale);

        //
        // Prepare canvas using PDF page dimensions
        //

        //canvas.height = viewport.height;
            canvas.height = 800;
        //canvas.width = viewport.width;
            canvas.width = 800;
            context.globalAlpha = 0.5;  


        //
        // Render PDF page into canvas context
        //
        var renderContext = {
          canvasContext: context,
          viewport: viewport
        };


        page.render(renderContext);
        context.restore();  


      });
    });
}

Trying out following code for panning:

var isDown = false;
        var startCoords = [];
        var last = [0, 0];

        canvas.onmousedown = function(e) {
            isDown = true;

            startCoords = [
                e.offsetX - last[0],
                e.offsetY - last[1]
           ];
        };

        canvas.onmouseup   = function(e) {
            isDown = false;

            last = [
                e.offsetX - startCoords[0], // set last coordinates
                e.offsetY - startCoords[1]
            ];
        };

        canvas.onmousemove = function(e)
        {
            if(!isDown) return;

            var x = e.offsetX;
            var y = e.offsetY;
            context.setTransform(1, 0, 0, 1,
                             x - startCoords[0], y - startCoords[1]);
            pdfCanvas(scale)
        }   

Answer 1

Recommend you using the following plugin

http://borbit.github.io/jquery.viewport/

The only thing you have to do is to create an viewport (eg div) and define the width and height that is smaller than your canvas.

Answer 2

您还可以使用“手动工具”，它只是...