/*页面data定义所需参数*/
data{
    // canvas 
    _width: 0, //手机屏宽
    _heigth: 0,//手机屏高
    swiperHeight: 0,//主图图片高度
    canvasType: false//canvas是否显示
    loadImagePath: \'\',//下载的图片
    imageUrl: \'http://imgo2o.shikee.com/goods/2019/10/17/201910171144361688.jpg\', //主图网络路径
    codeUrl: \'http://imgo2o.shikee.com/couponqrcode/2019/10/18/86_215.jpg\',//二维码网络路径
    localImageUrl: \'\', //绘制的商品图片本地路径
    localCodeUrl: \'\', //绘制的二维码图片本地路径
    loadType: flase  //保存图片，分享好友 Btn
}

/* 图片加载时 页面加载主图时触发
 <image src="{{item}}" class="img" mode="widthFix" bindload="onSwiperLoad"></image>
*/
onImgLoad: function(e) {
    let oImgW = e.detail.width; //图片原始宽度
    let oImgH = e.detail.height; //图片原始高度
    let imgWidth = 750; //图片设置的宽度
    let scale = imgWidth / oImgW; //比例计算
    let imgHeight = oImgH * scale;

    this.setData({
        swiperHeight: imgHeight,
    })
}

/*按生成图片按钮时*/
getSysInfo: function() {
    /*获取手机宽高*/
    let that = this
    let imgUrl = this.data.imageUrl
    let qrcodeUrl = this.data.codeUrl
    wx.getSystemInfo({
        success(res) {
            that.setData({
                _width: res.windowWidth,
                _heigth: res.windowHeight,
                canvasType: true,
            })
            // 获取图片信息生成canvas
            that.getImginfo([imgUrl, qrcodeUrl], 0);
        }
    })
}

// 获取图片信息
getImginfo: function(urlArr, _type) {
    let that = this;
    wx.getImageInfo({
        src: urlArr[_type], //服务器返回的带参数的小程序码地址
        success: function(res) {
            //res.path是网络图片的本地地址
            if (_type === 0) { //商品图片
                that.setData({
                    localImageUrl: res.path,
                })
                that.getImginfo(urlArr, 1)
            } else {
                that.setData({ //二维码
                    localCodeUrl: res.path,
                    loadType: true,
                })
                // 创建canvas图片
                that.createNewImg();
            }
        },
        fail: function(res) {
            //失败回调
            console.log(\'错误-res\', _type, res)
        }
    });
},

//绘制canvas
createNewImg: function() {
    let _width = this.data._width,
        _heigth = this.data._heigth; //屏幕宽与高

    let imgHeigth = this.data.swiperHeight, //原图片高度
        scale = (_width - 40) / _width, //缩小比例
        that = this;
    let imgH = imgHeigth * scale; //绘制时图片显示高度  
    let ctx = wx.createCanvasContext(\'mycanvas\');
    // 绘制背景
    ctx.setFillStyle("#fff");
    ctx.fillRect(0, 0, _width - 40, imgH + 160);
    //绘制图片
    ctx.drawImage(this.data.localImageUrl, 10, 10, _width - 60, imgH);

    // 绘制标题
    ctx.setFontSize(18);
    ctx.setFillStyle(\'#333\');

    let txtWidth = _width - 60 + 30 - 100 - 50; //文字的宽度

    //商品名称 最多两行显示 写法有点LOW，但思路是这样的
    let title = this.data.goods.title; //商品名称
    let title2; //商品名称
    if (title.length > 10) {
        title2 = title.slice(10, title.length);
        title = title.slice(0, 10);
    }
    if (title2.length > 10) {
        title2 = title2.slice(0, 9) + \' ...\';
    }
    ctx.fillText(title, 10, imgH + 40, txtWidth);
    ctx.fillText(title2, 10, imgH + 70, txtWidth);
    // 绘制价格 \'￥\'
    ctx.setFontSize(14);
    ctx.setFillStyle(\'#d2aa68\');
    ctx.fillText(\'￥\', 10, imgH + 110, txtWidth);
    // 绘制价格
    ctx.setFontSize(24);
    ctx.fillText(this.data.goods.promotion_price, 26, imgH + 110, txtWidth);
    // 绘制门市价
    ctx.setFontSize(14);
    ctx.setFillStyle(\'#666\');
    ctx.fillText(`门市价￥${this.data.goods.price}`, 115, imgH + 110, txtWidth);

    // 绘制二维码
    ctx.drawImage(this.data.localCodeUrl, _width - 80 + 80 - 150, imgH + 20, 100, 100);
    // 显示绘制
    ctx.draw();

    //将生成好的图片保存到本地，需要延迟一会，绘制期间耗时
    setTimeout(function() {
        wx.canvasToTempFilePath({
            canvasId: \'mycanvas\',
            success: function(res) {
                var tempFilePath = res.tempFilePath;
                that.setData({
                    loadImagePath: tempFilePath,
                });
            },
            fail: function(res) {
                console.log(res);
            }
        });
    }, 500);
}

//点击保存到相册
saveImg: function() {
    wx.saveImageToPhotosAlbum({
        filePath: this.data.loadImagePath,
        success(res) {
            console.log(\'res\', res);
            wx.showToast({
                title: \'已保存到相册\',
                icon: \'success\',
                duration: 3000
            })
        }
    })
}

// 关闭 海报弹窗
closePos: function() {
    this.setData({
        canvasType: false
    });
}

<view class=\'poster\' wx:if="{{canvasType}}">
  <canvas class=\'canvas\' style=\'height:{{canvasH}}px;width:{{canvasW}}px;\' canvas-id="mycanvas" />

  <cover-view class=\'opt\' hidden=\'{{!loadType}}\'>
    <cover-view class=\'cont\'>
      <cover-view class=\'item\' bindtap=\'saveImg\'>
        <cover-image  class=\'ico\' src=\'{{server_img_url}}ico/icon_download.png\'></cover-image>
        <cover-view>保存到相册</cover-view>
      </cover-view>
     
    </cover-view>
  </cover-view>
  <cover-view class=\'btn-box\' hidden=\'{{!loadType}}\'>
    <button bindtap=\'closePos\' class=\'btn\'>取消</button>
  </cover-view>
</view>

<view class="btn-box">
    <button class=\'m-btn-share\' bindtap=\'getSysInfo\'>生成图片</button>
    <button class=\'m-btn\' open-type=\'share\'>call友来抢</button>
</view>