wx.getImageInfo({ src: '/pages/exp/image/bean.png', success: (res) => {   const image = canvas.createImage();   image.src = '/pages/exp/image/bean.png';   if (image.src) {     console.info("image found: " + image.src);   } else {     console.info("image not found");   } } }); 这段代码，在微信开发工具上打印出"image found: pages/exp/image/bean.png"，但预览出二维码，在手机上访问小程序，打印出"image found: "，看image.src是空，请问什么原因呢