API wx.createCanvasContext 微信版本:8.0.21 基础库版本2.21.4

按照API介绍调用drawImage，canvas画布上仍是空白。

<van-button bind:click="chooseImage">上传</van-button>
<!--用于生成压缩图片的canvas画布，在视图区域外-->
<view>
    <canvas canvas-id="zipCanvas" style="width:{{imageWidth}}px;height:{{imageHeight}}px;"></canvas>
</view>
chooseImage(){
  const vm=this;
  let ctx=wx.createCanvasContext('zipCanvas');
  wx.chooseImage({
    success(res){
      console.log(res);
      ctx.drawImage(res.tempFilePaths[0],0,0,150,100);
      ctx.draw();
    }
  });
}