这个代码写的有问题？安卓和模拟器界面都正常，ios端界面只有1/4
const canvas = wx.createCanvas();
const ctx = canvas.getContext('2d'); 
const windowInfo = wx.getSystemInfoSync();
const dpr = windowInfo.pixelRatio;
canvas.width = windowInfo.screenWidth * dpr;
canvas.height = windowInfo.screenHeight * dpr;
ctx.scale(dpr, dpr);
ctx.imageSmoothingEnabled = false;