- 需求的场景描述（希望解决的问题）

-使用画布得到的输出的图在开发者工具预览显示这个

composePic: function(id, pic, cb) {

const ctx = wx.createCanvasContext(id)

let offset_x = 18

let offset_y = 7

let w = 96

let h = 100

ctx.drawImage('../../img/map/bg.png', 0, 0, w, h)

ctx.save()

ctx.beginPath()

ctx.arc(30 + offset_x, 30 + offset_y, 30, 0, 2 * Math.PI)

ctx.clip()

ctx.drawImage(pic, offset_x, offset_y, 60, 60)

ctx.restore()

ctx.draw(false, function() {

wx.canvasToTempFilePath({

x: 0,

y: 0,

width: w,

height: h,

canvasId: id,

success(res) {

console.log(res.tempFilePath)

cb(res.tempFilePath)

}

})

})

},