wx.getImageInfo({

src: result,

success: function (res) {

let originWidth, originHeight;

originHeight = res.height;

originWidth = res.width;

console.log("the origin width:" + originWidth + " the origin height:" + originHeight);

//压缩比例

// 最大尺寸限制

let maxWidth = 300,

maxHeight = 100;

// 目标尺寸

let targetWidth = originWidth,

targetHeight = originHeight;

//等比例压缩，如果宽度大于高度，则宽度优先，否则高度优先

if (originWidth > maxWidth || originHeight > maxHeight) {

if (originWidth / originHeight > maxWidth / maxHeight) {

// 要求宽度*(原生图片比例)=新图片尺寸

targetWidth = maxWidth;

targetHeight = Math.round(maxWidth * (originHeight / originWidth));

} else {

targetHeight = maxHeight;

targetWidth = Math.round(maxHeight * (originWidth / originHeight));

}

}

//更新canvas大小

that.setData({

cw: targetWidth,

ch: targetHeight

});

const query = wx.createSelectorQuery()

query.select('#zipCanvas')

.fields({

node: true,

size: true

})

.exec(async res => {

// 获取 canvas 实例

const canvas = res[0].node

// 获取 canvas 绘图上下文

const ctx = canvas.getContext('2d')

// 根据设备dpr处理尺寸

const dpr = wx.getSystemInfoSync().pixelRatio

canvas.width = targetWidth * dpr

canvas.height = targetHeight * dpr

console.log('canvas.width, canvas.height', canvas.width, canvas.height)

ctx.scale(dpr, dpr)

// 将图片绘制到 canvas

ctx.drawImage(result, 0, 0, targetWidth, targetHeight)

setTimeout(function () {

// 将canvas图片上传到微信临时文件

wx.canvasToTempFilePath({

canvas,

x: 0,

y: 0,

destWidth: targetWidth,

destHeight: targetHeight,

complete(res) {

if (res.errMsg === 'canvasToTempFilePath:ok') {

// 返回临时文件路径

that.uploadImg(res.tempFilePath)

}

},

fail(err) {

wx.hideLoading();

wx.showToast({

title: '电子签名压缩失败',

icon: 'none',

duration: 2000

});

}

})

}, 1000);

})

}

})

拿到的图片为空白，请大佬帮帮解决一下，多谢！！！