小程序 图片转base64然后上传的坑点

　　　　　　　　　　const self = this

                const ctx = wx.createCanvasContext(‘myCanvas‘)
                const platform = wx.getSystemInfoSync().platform
                const imgWidth = 60, imgHeight = 60;
                wx.chooseImage({
success: res => {
    //生成的图片临时路径画成canvas
    ctx.drawImage(res.tempFilePaths[0], 0, 0, imgWidth, imgHeight)
    ctx.draw(false, () => {
        self.drawFinish = true
        wx.canvasGetImageData({
            canvasId: ‘myCanvas‘,
            x: 0,
            y: 0,
            width: imgWidth,
            height: imgHeight,
            success: res => {
                if (platform === ‘ios‘) {
// 兼容处理：ios获取的图片上下颠倒
res = this.reverseImgData(res)
                }
                // 3. png编码
                let pngData = upng.encode([res.data.buffer], res.width, res.height)
                // 4. base64编码

                let base64 = wx.arrayBufferToBase64(pngData)
                debugger
                console.log(‘data:image/jpeg;base64,‘ + base64)
                this.setData({
avatarUrl: ‘data:image/jpeg;base64,‘ + base64
                });
            },
            fail(res) {
                debugger
                console.log(res)
            },
        })
    })
}
                })