Drawing Text
Rendering text in regular HTML is easy, rendering text in an HTML5 Canvas is a little more involved but the effects that can be applied to text is greater than that of plain HTML and CSS. Here we show how to render some basic text using a variety of fonts, colors and font weights.
<body onload="drawCanvas();">
<div>
<canvas id="myCanvas" width="500" height="150">
<p>Your browser doesn't support canvas.</p>
</canvas>
</div>
</body>
function drawCanvas() {
// Get our Canvas element
var surface = document.getElementById("myCanvas");
if (surface.getContext) {
// If Canvas is supported
var context = surface.getContext('2d');
// Set the baseline
context.textBaseline = "top";
// Draw some text in Arial
context.font = "30px Arial";
context.fillStyle = "#ff0000";
context.fillText("30px Arial Text", 10, 10);
}
}
Firstly we set the font property, this property can contain the font name and size as well as the font weight, here we set it to Arial, 30px in size. The fillStyle controls how the text is painted onto the canvas, here we set it to a solid Red.
Finally we call the fillText method that does that actual text rendering, this method takes the text string to draw and the x and y position from the top-left of the canvas.
// Now some in Times New Roman Blue
context.font = "25px Times New Roman";
context.fillStyle = "#0000ff";
context.fillText("25px Times New Roman Text", 10, 40);
// And some in Tahoma Bold
context.font = "bold 15px Tahoma";
context.fontweight
context.fillStyle = "#000000";
context.fillText("15px Tahoma Bold Text", 10, 70);
Gradient Fills
So far we could have displayed the above text using standard HTML and CSS, however when using the Canvas to draw text you have a whole lot more possibilities, one of these is the ability to apply gradients to text:
context.font = "30px Arial";
var gradient = context.createLinearGradient(0, 0, 0, 40);
// Add 2 steps to it
gradient.addColorStop(0, "rgb(100,0,0)");
gradient.addColorStop(1, "rgb(255,0,0)");
// Assign our gradient to the fillStyle
context.fillStyle = gradient;
context.fillText("30px Arial Text with Red Gradient", 10, 10);
Here we create a vertical gradient that flows from dark Red to bright Red. For more details on using gradients and fill styles please see the Shapes and Fill Styles tutorial.
Measuring Text
A common requirement when dealing with text is to be able to measure how many pixels a block of text occupies. For this we can use the measureText() method that can be found on the graphics context:
var size = context.measureText("Some text to measure");
alert(size.width);
This method returns a size object which contains the text dimensions.
Rendering Text on the iPad
If you intend to run your HTML5 application on an iPad then there is a bug present that causes text to not render correctly, however thanks to some 3rd party script there is an alternative. StrokeText is the best text rendering solution out there that is compatible with the iPad, details of the API and to download it please visit the StrokeText site.
Rate this:
1 Star
2 Star
3 Star
4 Star
5 Star
4 Ratings / 3.3 Average