JS:

wx.getImageInfo({

src: tempFilePaths[0],

success: function (res) {

var ctx = wx.createCanvasContext('photo_canvas');

var canvasWidth = res.width

var canvasHeight = res.height;

var str = canvasWidth / canvasHeight;

if (str > 1) {

console.log('heng')

if (canvasWidth > _this.data.screenWidth){

canvasHeight = _this.data.screenHeight;

canvasWidth = str * canvasHeight;

//横版图片

_this.setData({

canvasHeight: canvasHeight,

canvasWidth: canvasWidth,

})

} else {

_this.setData({

canvasHeight: canvasHeight,

canvasWidth: canvasWidth,

})

}

} else {

if (canvasHeight > _this.data.screenHeight){

canvasWidth = _this.data.screenWidth;

canvasHeight = canvasWidth / str;

//竖版图片

_this.setData({

canvasWidth: canvasWidth,

canvasHeight: canvasHeight,

})

} else {

_this.setData({

canvasWidth: canvasWidth,

canvasHeight: canvasHeight,

})

}

}

//设置canvas尺寸

ctx.drawImage(tempFilePaths[0], 0, 0, canvasWidth, canvasHeight)

ctx.draw(true, function () {

});

}

})

WXML:

<canvas canvas-id="photo_canvas" style="width:{{canvasWidth}}px;height:{{canvasHeight}}px;position: absolute;left:0px;top:0px; "></canvas>

这样可以吗？