async onLoad(){
var that = this;
wx.downloadFile({
url: that.imgStr, // 资源地址
success(res) {
// 只要服务器有响应数据，就会把响应内容写入文件并进入 success 回调，业务需要自行判断是否下载到了想要的内容
if (res.statusCode === 200) {
that.imgFilePath = res.tempFilePath;
that.$apply();
that.drawImg();
console.log(res);
}
}
})
that.$apply();


/* ctx.draw(false, function () {
// wx.canvasToTempFilePath这个一定要写在ctx.draw里面的回调里面，是坑勿跳
wx.canvasToTempFilePath({
canvasId: "shareCanvas",
destWidth: 600,
destHeight: 800,
quality: 1,
success: function (res) {
console.log(res.tempFilePath)
callback(res.tempFilePath)
},
fail: function (res) {
console.log(res)
}
})
}) */

}

async drawImg(){
var postersize = this.setCanvasSize(750);//动态设置画布大小
console.log(postersize);
const ctx = wx.createCanvasContext('shareCanvas',this);

console.log(this.imgFilePath);

ctx.drawImage(this.imgFilePath, 0, 0, postersize.w, postersize.h);
ctx.drawImage(this.imgFilePath, 30, 30, postersize.w, postersize.h);
console.log(this.imgFilePath);
ctx.draw();
}

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