Canvas Game Essentials - HTML5 Canvas - page 391

var width = 20;
var height = 20;
function drawScreen() {
// draw background and text
context.fillStyle = '#000000';
context.fillRect(0, 0, 200, 200);
context.fillStyle = '#ffffff';
context.font = '20px _sans';
context.textBaseline = 'top';
context.fillText ("Player Ship - rotate", 0, 180);
//transformation
var angleInRadians = rotation * Math.PI / 180;
context.save(); //save current state in stack
context.setTransform(1,0,0,1,0,0); // reset to identity
//translate the canvas origin to the center of the player
context.translate(x+.5*width,y+.5*height);
context.rotate(angleInRadians);
//drawShip
context.strokeStyle = '#ffffff';
context.beginPath();
//hardcoding in locations
context.moveTo(0,-10);
context.lineTo(9,9);
context.lineTo(0,-1);
context.moveTo(-1,-1);
context.lineTo(-10,9);
context.lineTo(-1,-10);
/*
//using the width and height to calculate
context.moveTo(10-.5*width,0-.5*height);
context.lineTo(19-.5*width,19-.5*height);
context.lineTo(10-.5*width,9-.5*height);
context.moveTo(9-.5*width,9-.5*height);
context.lineTo(0-.5*width,19-.5*height);
context.lineTo(9-.5*width,0-.5*height);
*/
context.stroke();
context.closePath();
//restore context
context.restore(); //pop old state on to screen
//add to rotation
rotation++;
}