From w3schools:
The createLinearGradient method creates a gradient object that changes from one color to another. <br />
You can specify how and where these changes will take place, using the coordinate parameters. <br />
The x0 and y0 parameters represents the start coordinates of the gradient. <br />
The x1 and y1 parameters represents the end coordinates of the gradient.
http://www.w3schools.com/html5/canvas_createlineargradient.asp[
^]
I wonder if looking at Google is so difficult?