图上为开发者工具上生成的图片。

图上为iphone6sp 生成的图片，头像变成方的了。

以下为代码，麻烦帮忙看下是什么问题。

canvas: function () {

var that = this

var context = wx.createCanvasContext('ass')

var avatarurl_widths = 150;

var avatarurl_heigths = 150;

var avatarurl_xs = that.data.width * 0.5 - 75;

var avatarurl_ys = that.data.height * 0.63;

var avatarurl_width = 70;

var avatarurl_heigth = 70;

var avatarurl_x = that.data.width * 0.5-35;

var avatarurl_y = 5;

context.drawImage(that.data.downbj, 0, 0, that.data.width, that.data.height);

context.setTextAlign('center')

context.setFontSize(20)

context.setFillStyle('#fd943f')

context.fillText('用' + that.data.shopname, that.data.width * 0.5, 110)

context.save();

context.beginPath();

context.arc(avatarurl_widths / 2 + avatarurl_xs, avatarurl_heigths / 2 + avatarurl_ys, avatarurl_widths / 2, 0, Math.PI * 2, false);

context.clip();

context.drawImage(that.data.downimage, avatarurl_xs, avatarurl_ys, avatarurl_widths, avatarurl_heigths);

context.restore();

context.arc(avatarurl_width / 2 + avatarurl_x, avatarurl_heigth / 2 + avatarurl_y, avatarurl_width / 2, 0, Math.PI * 2, false);

context.clip();

context.drawImage(that.data.downpt, avatarurl_x, avatarurl_y, avatarurl_width, avatarurl_heigth);

context.restore();

context.draw();

context.stroke()

},