imageOnLoad(ev) {

console.log(ev);

var _this = this;

//放大镜效果

var bannerUrl = _this.data.url_com + _this.data.bannerUrl;

var wImg = ev.detail.width;

var hImg = ev.detail.height;

var width = parseFloat(_this.data.width);

console.log(bannerUrl);

console.log(wImg);

console.log(hImg);

console.log(width);

var ctx = wx.createCanvasContext('myCanvas');

ctx.drawImage(bannerUrl, 0, 0, wImg, hImg, 0, 0, width, width);

ctx.draw();

},

域名配置好了，图片是加载完成才绘制的

求大神帮我解答一下！！！！！！！！！！！！！！！！！