Getting canvas context from elsewhere in the script

I have a script that draws an image on a canvas and allows people to draw lines on this image. I want to get the context from elsewhere in the script (i.e. a header that has various jQuery functions). Is this possible?

What I mean is something like:

Header:

saveInfo = function ()
{
   //save all the inputs

   //get the context of the canvas so we can find some properties
}

clearInfo = function ()
{
   //clear the inputs

   //get the context of the canvas so we can clear it and redraw the main image
}

Included File

<script type="text/javascript">
   //this is the script开发者_StackOverflow社区 that produces the drawing functionality initially that I already have
</script>

Edit: I realise this may seem obvious so to embellish, whenever someone draws a line on the canvas in the included script I add to a json array called paths. I need to be able to get this in the save section.

var context = document.getElementById("myCanvasId").getContext("2d");

... will work in any place in your script.

Instead of reaching into the canvas directly, why not create global functions to perform the semantic actions you want? For example:

saveInfo = function(){
 // save all the inputs
   var props = getContextProperties();
};

clearInfo = function(){
  // clear the inputs
  redrawCanvas();
};

$(function(){
  var canvas = $('canvas')[0];
  var ctx = canvas.getContext('2d');
  getContextProperties = function(){
    return { w:canvas.width, h:canvas.height };
  };
  redrawCanvas = function(){
    ctx.save();
    ctx.setTransform(1,0,0,1,0,0);
    ctx.clearRect(0,0,canvas.width,canvas.height);
    ctx.restore();
    ctx.beginPath();
    // ... 
  };
});