Openstreet map static image

i want to create static map for openstreet map which is implemented in Openlayer 2 , Image generated by my code does not contain entire map. It loses tiles.

Kindly help

i have used following html2canvas code

onrendered: function (canvas) {
//Set hidden field's value to image data (base-64 string)
$('#childPagePlaceHolder_img_val').val(canvas.toDataURL().replace(/^data[:]image\/(png|jpg|jpeg)[;]base64,/i, ""));//canvas.toDataURL("image/png"));
//Submit the form manually
left: 0,
top: 0,
"transform": transform