Question

I’m currently using HTML5’s canvas to render a number of strings using the fillText method. This works fine, but I’d also like to give each string a 1px black outer stroke. Unfortunately the strokeText function seems to apply an inner stroke. To counter this, I’ve written a drawStrokedText function that achieves the effect I’m after. Unfortunately it’s horrible slow (for obvious reasons).

Is there a fast, cross-browser way of achieving a 1px outer stroke using native canvas functionality?

drawStrokedText = function(context, text, x, y)
{
    context.fillStyle = "rgb(0,0,0)";
    context.fillText(text, x-1, y-1);
    context.fillText(text, x+1, y-1);
    context.fillText(text, x-1, y);
    context.fillText(text, x+1, y);
    context.fillText(text, x-1, y+1);
    context.fillText(text, x+1, y+1);

    context.fillStyle = "rgb(255,255,255)";
    context.fillText(text, x, y);
};

Here’s an example of the effect at work:

Answer 1

What’s wrong with stroke? Since half the stroke will be outside of the shape, you can always draw the stroke first with a line width of double what you want. So if you wanted a 4px outer stroke you could do:

function drawStroked(text, x, y) {
    ctx.font = '80px Sans-serif';
    ctx.strokeStyle = 'black';
    ctx.lineWidth = 8;
    ctx.strokeText(text, x, y);
    ctx.fillStyle = 'white';
    ctx.fillText(text, x, y);
}


drawStroked("37°", 50, 150);

Which makes:

live fiddle here: http://jsfiddle.net/vNWn6/

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IF that happens to not look as accurate at smaller text rendering scales, you can always draw it large but scale it down (in the above case you’d do ctx.scale(0.25, 0.25))