php画布 html5实现一个简单的画板

我们先来看看实现效果：

(推荐教程：h5)

实现代码如下：

var c = document.getElementById('canvas');

var ctx = c.getContext('2d');

//画一个黑色矩形

ctx.fillStyle = 'black';

ctx.fillRect(0,0,600,300);

//按下标记

var onoff = false;

var oldx = -10;

var oldy = -10;

//设置颜色

var linecolor = 'white';

//设置线宽

var linw = 4;

//添加鼠标移动事件

canvas.addEventListener('mousemove',draw,true);

//添加鼠标按下事件

canvas.addEventListener('mousedown',down,false);

//添加鼠标弹起事件

canvas.addEventListener('mouseup',up,false);

function down(event) {

onoff = true;

oldx = event.pageX-10;

oldy = event.pagey-10;

}

function up() {

onoff = false;

}

function draw(event) {

if(onoff == true) {

var newx = event.pageX-10;

var newy = event.pageY-10;

ctx.beginPath();

ctx.moveTo(oldx,oldy);

ctx.lineTo(newx,newy);

ctx.strokeStyle = linecolor;

ctx.lineCap = 'round';

ctx.stroke();

oldx = newx;

oldy = newy;

}

}

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