ipad html5 画图工具栏,如何借鉴HTML5画布多圈iPad上

它是在同一时间只绘制一个圆，但要同时绘制多个圆即在iPad上查看多个圈如何借鉴HTML5画布多圈iPad上

//touch events for circle

var canvas = document.getElementById('paint'),

ctx = canvas.getContext("2d"),

w = canvas.width,

h = canvas.height, circle = {}, drag_circle= false;

听众绘制圈

tmp_canvas.addEventListener("touchstart", touchHandler_circle, false);

tmp_canvas.addEventListener("touchmove", touchHandler_circle, false);

tmp_canvas.addEventListener("touchend", touchHandler_circle, false)

函数来处理事件

function touchHandler_circle(event) {

if (event.targetTouches.length == 1) {

var touch = event.targetTouches[0];

if (event.type == "touchstart")

{

circle.X= touch.pageX;

circle.Y= touch.pageY;

drag_circle= true;

}

else if (event.type == "touchmove") {

if (drag_circle) {

tmp_ctx.clearRect(0, 0, tmp_canvas.width, tmp_canvas.height);

circle.width = touch.pageX +circle.X;

circle.height = touch.pageY +circle.Y ;

//radius

var radius= Math.max(Math.abs(touch.pageX -circle.X),

Math.abs(touch.pageY -circle.Y))/2;

tmp_ctx.beginPath();

tmp_ctx.arc(circle.width,circle.height,radius,0,Math.PI*2,false);

tmp_ctx.stroke();

tmp_ctx.closePath();

draw_circle_ipad();

}

} else if (event.type == "touchend" || event.type == "touchcancel") {

drag_circle = false;

}

}

+0

什么是'tmp_ctx'？它从何而来？你可以创作一个小提琴吗？ –