HTML5 Canvas, 2nd Edition

Linear Gradients and Text

To create a linear gradient, make a call to the context’s createLinearGradient() method to create a Gradient object. The createLinearGradient() method accepts four parameters that all define the line of the linear gradient. The x0 and y0 parameters are the starting point of the line, and x1 and y1 represent the ending point of the line:

var gradient = context.createLinearGradient( [x0],[y0],[x1],[y1]);

For example, if you want to create a linear gradient that starts at the beginning of the text (located at 100,100) and has an endpoint that is the width of your text as displayed on the canvas, you might write the following code:

var metrics = context.measureText(message);
var textWidth = metrics.width;
var gradient = context.createLinearGradient(100, 100, textWidth, 100);

After you have created the line that represents the gradient, you need to add colors that will form the gradations of the gradient fill. This is done with the addColorStop() method, which requires two arguments, offset and color:

gradient.addColorStop([offset],[color]);

offset

This is the offset on the gradient line to start the color gradation. The entire gradient is represented by the numbers between 0.0 and 1.0. The offset will be a decimal that represents a percentage.

color

A valid CSS color in the format “#RRGGBB”.

So, if you want black to be the first color in the gradient and red to be the second color that starts halfway down the gradient line, you would create two calls to addColorStop() ...