Html游戏开发-画图

var canvas = document.getElementById(‘canvas‘),
    context = canvas.getContext(‘2d‘);

context.lineWidth = 30;

context.font = ‘24px Helvetica‘;
context.fillText(‘Click anywhere to erase‘, 175, 40);

context.strokeRect(75, 100, 200, 200);
context.fillRect(325, 100, 200, 200);

// 鼠标按下时清除整个画布
context.canvas.onmousedown = function (e) {
   context.clearRect(0, 0, canvas.width, canvas.height);
};

var canvas = document.getElementById(‘canvas‘),
    context = canvas.getContext(‘2d‘),
    gradient = context.createRadialGradient(
                 canvas.width/2, canvas.height, 10,
                 canvas.width/2, 0, 100);

gradient.addColorStop(0, ‘blue‘);
gradient.addColorStop(0.25, ‘white‘);
gradient.addColorStop(0.5, ‘purple‘);
gradient.addColorStop(0.75, ‘red‘);
gradient.addColorStop(1, ‘yellow‘);

context.fillStyle = gradient;
context.rect(0, 0, canvas.width, canvas.height);
context.fill();