canvas怎么可以使图片全部显示出来，跪求方法

var pw = wx.getSystemInfoSync().windowWidth;

var ph = wx.getSystemInfoSync().windowHeight;

var headImage = app.globalData.userInfo.avatarUrl;

var content = wx.createContext(“qrcodeCanvas”);

content.drawImage(“…/…/images/qrcode_banner.jpg”, 0, 0, pw, pw / 104 * 59);

content.drawImage(“…/…/images/ewm.png”, pw / 2 - pw / 2 / 2, ph / 16 * 12 - ph / 16 * 4, pw / 2, pw / 2);//二维码图片

content.restore()

content.drawImage(headImage, pw / 2 - pw / 8 / 2, ph / 16 * 12 - ph / 16 * 4 + pw / 2 / 2 - pw / 8 / 2, pw / 8, pw / 8);//二维码中间的图片

content.setStrokeStyle(‘black’);

content.setFontSize(16);

content.setTextAlign(‘center’)

content.fillText(“长按图片识别二维码”, pw / 2, ph / 16 * 12 - ph / 16 * 4 + pw / 2 + 25)

wx.drawCanvas({

canvasId: “qrcodeCanvas”,

actions: content.getActions(),

reserve: true

})

二维码下面还有一张图片，加载太快了就到下面去了，怎么把它弄上来