base64格式的图片怎么在微信小程序中展示出来

可以使用wx.base64ToArrayBuffer()将base64格式的图片转换为ArrayBuffer，然后将其传递给wx.createImageBitmap()创建一个图片位图，最后将位图渲染到canvas或image组件中。示例代码如下：

// 将base64格式的图片转换为ArrayBuffer
const base64 = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAABHUlEQVQ4T5XSvyuEYRTH8c+ZkN5pjQ2Fm5G5X0x5xgC1yNwZLkO1Nc2MjmRiZS4kNj/4MGzEK3g4B4i4d71KfJp5MnZtlaDZMfjKQh5X5J5x5/Yz7t7/Mb09gGBiBgbgFQaS6SAdgJ4C9gNeC3gH4D4gH4E3wO4G3wK4F3wK3G3wK3G3wO4G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK7Dvv/8Zu8f9L+OJg1jyOAAAAABJRU5ErkJggg==';
const arrayBuffer = wx.base64ToArrayBuffer(base64);

// 创建一个图片位图
wx.createImageBitmap({
  data: arrayBuffer,
  width: 100,
  height: 100,
  success: (res) => {
    // 将位图渲染到canvas组件中
    const ctx = wx.createCanvasContext('myCanvas');
    ctx.drawImage(res, 0, 0, 100, 100);
    ctx.draw();
  }
});

另外，如果需要在image组件中展示base64格式的图片，也可以使用setData()将图片数据传递给image组件的src属性。示例代码如下：

// 将base64格式的图片转换为dataUrl
const base64 = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAABHUlEQVQ4T5XSvyuEYRTH8c+ZkN5pjQ2Fm5G5X0x5xgC1yNwZLkO1Nc2MjmRiZS4kNj/4MGzEK3g4B4i4d71KfJp5MnZtlaDZMfjKQh5X5J5x5/Yz7t7/Mb09gGBiBgbgFQaS6SAdgJ4C9gNeC3gH4D4gH4E3wO4G3wK4F3wK3G3wK3G3wO4G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK3G3wK7Dvv/8Zu8f9L+OJg1jyOAAAAABJRU5ErkJggg==';
const dataUrl = base64.replace(/^data:image\/\w+;base64,/, '');

// 将dataUrl传递给image组件的src属性
this.setData({
  imageUrl: `data:image/png;base64,${dataUrl}`
});

在wxml文件中，可以使用image组件展示图片：

<image src="{{imageUrl}}"></image>