const ctx = wx.createCanvasContext('myCanvas')
        ctx.drawImage(res.tempImagePath, 0, 0, 512, 512)
        ctx.draw()
        wx.canvasToTempFilePath({
          x: 0,
          y: 0,
          width: 512,
          height: 512,
          canvasId: 'myCanvas',
          success(res) {
            wx.getFileSystemManager().readFile({
              filePath: res.tempFilePath,
              encoding: 'base64',
              success: res => {
              
              },
              fail: res => {
                console.log(res)
              }
            })
          }
        })

发现苹果跟安卓绘制出来的图片px大小并不统一512px, 哪里写错了吗？