【微信小程序生成海报保存到相册】

微信小程序生成海报保存到相册

如图
需要先有设计图的尺寸

在canvas绘图时，通常会遇到的一种情况是用固定宽高来显示图片，如果直接把图片内容填充进去的话，显示出来的图片就会被压扁或者被挤瘦，其效果简直不忍直视！那么，就需要把图片进行拉伸、压缩或裁剪。

接下来，先给 drawImage 做个介绍：

canvas的drawImage函数可以 绘制图像到画布。

它有以下参数：

参数 类型 说明

这里再来一张图

它有三种写法：

1. 只规定原始图片开始剪切的位置，默认填充剩余宽高到画布上

drawImage(imageResource, dx, dy)

2. 从指定位置裁剪原始图片指定宽高，填充到画布上

drawImage(imageResource, dx, dy, dWidth, dHeight)

3. 从指定位置裁剪原始图片指定宽高，从指定位置开始显示到画布上指定宽高

drawImage(imageResource, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight)

这里如果需要裁剪图片的话需要用到第三种。

因为分享商品图片的话，图片的大小不固定，需要裁剪。
裁剪图片，借鉴这里

<view class="container">
    <button catchtap="showPic">点击生成海报button>

    
    <view class="share-cover" wx:if="{{showSharePic}}" catchtouchmove='true' catchtap='closeShare'>
    view>
    <view class="share-pic-box" wx:if="{{showSharePic}}" >
        <view class="share-pic">
            <image src="{{sharePicUrl}}" class="sharePic">image>
        view>
        <button class="share-tips" catchtap='savePic'>保存图片button>
        
    view>
    

    
    <canvas canvas-id="shareFrends" class="canvas">canvas>
    
view>
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/* fx */
.share-cover {
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    background: rgba(0, 0, 0, .5);
    z-index: 101;
}

.share-pic-box {
    width: 640rpx;
    height: 1080rpx;
    border-radius: 24rpx;
    left: 50%;
    top: 45%;
    transform: translate(-50%, -50%);
    position: absolute;
    z-index: 999;
}

.share-pic {
    width: 640rpx;
    height: 1080rpx;
    border-radius: 24rpx;
    background: #fff;
    margin-bottom: 40rpx;
    overflow: hidden;
}

.share-tips {
    width: 70% !important;
    height: 44px;
    box-sizing: border-box;
    background: #FF3B3B;
    opacity: 1;
    border-radius: 22px;
    font-size: 16px;
    font-family: PingFang SC;
    font-weight: 400;
    line-height: 44px;
    color: #FFFFFF;
    padding: 0 !important;
}

/* .close-share {
    width: 50rpx;
    height: 50rpx;
    position: absolute;
    top: -25rpx;
    right: -25rpx;
    border-radius: 50%;
    z-index: 101;
    background-color: #fff;
    background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAASBAMAAACk4JNkAAAALVBMVEUAAAAzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMFCKs1AAAADnRSTlMAAwGYnKilo/Tpjn6RhfLwgGgAAAB3SURBVAjXY7hxiAEEhLsZ+p4oABmMcS8Z7N45AVmi714xiL8DCjLGvTNiYKx75wQUeqzAABJUBAkxgARdwUIgwXcgIbAgVAik8QmEJQqUdYIKmYEFQWYp5gEFIcaLAQUhxjOCBP3AZokBXdAHMgso+JJh5yKoSwHamjhPbLDp2gAAAABJRU5ErkJggg==);
    background-size: 18rpx 18rpx;
    background-repeat: no-repeat;
    background-position: center center;
} */

.sharePic {
    width: 640rpx;
    height: 1080rpx;
}

.canvas {
    width: 1280rpx;
    height: 2160rpx;
    position: fixed;
    top: -1000000rpx;
}
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Page({

    /**
     * 页面的初始数据
     */
    data: {
        shareImg: '',
        shareTitle: '',
 // canvas 
        showSharePic: false, // 分享海报显示隐藏
        sharePicUrl: '', // 生成海报连接
        _selData: {
            logoUrl: 'https:166073915600099c29f.jpg', //分享图
            headIcon: 'https:1658494314000538a44.png', //头像
            codeLogo: 'https:xxx/1660812259000a6a8e7.png', //小程序码
            buyLogoUrl: 'https://xxx/1660814336000e3ccda.png', //采购图标
        },
        imgInfo: {},
    },
  

     // 生命周期函数--监听页面加载
    * //分享的主图，一进来就获取图片信息、或者在拿到该数据之后就获取信息

    onLoad: function (options) { {
      // 获取图片信息
      // var that = this;
      wx.getImageInfo({
          src: this.data.shareImg,//分享的主图，一进来就获取图片信息、或者在拿到该数据之后就获取信息
          success(res) {
              console.log(res);
              that.setData({
                  imgInfo: res,//存起来要用到
              })
          }
      })
   },
    
    showPic() {
        let sharePicUrl = this.data.sharePicUrl;
        if (sharePicUrl != '') {
            this.setData({
                showSharePic: true
            })
        } else {
            wx.showToast({
                title: '图片生成中',
                mask: true,
                icon: 'loading',
                duration: 100000
            })
            this.share = false
            let logo = '';
            let headIcon = '';
            let code = '';
            let buyLogo = '';
            this.getHead().then(headUrl => {
                headIcon = headUrl
                return this.getLogo()
            }).then(logoUrl => {
                logo = logoUrl;
                return this.getCode() //getBuyLogo
            }).then(codeUrl => {
                code = codeUrl
                // this.drawImg(logo, headIcon, code);
                return this.getBuyLogo() //getBuyLogo
            }).then(buyLogoUrl => {
                buyLogo = buyLogoUrl
                this.drawImg(logo, headIcon, code, buyLogo);
            })
        }
    },
    // 绘图
    drawImg(logo, headIcon, code, buyLogo) {
        console.log(logo)
        console.log(headIcon)
        console.log(code)
        console.log(buyLogo)

        // let title = '家用小型熨烫机便携式蒸汽熨斗家用小型熨烫机便携式蒸汽熨斗家用小型熨烫机便携式蒸汽熨斗家用小型熨烫机便携式蒸汽熨斗' // 标题
        let title = this.data.shareTitle // 标题
        let authorName = 'var 有缘' // 名称

        let w = 0
        wx.getSystemInfo({
            success: function (res) {
                w = res.screenWidth
            }
        })

        // 1
        let ctx = wx.createCanvasContext('shareFrends')
        ctx.fillStyle = '#ffffff';//---------------设置背景色
        ctx.fillRect(0, 0, w / 750 * 1080 * 2, w / 750 * 1080 * 2) //600*600


        //绘制logo--分享主图 
        //开始画 
       	var dw = 580 / this.data.imgInfo.width;
        var dh = 580 / this.data.imgInfo.height;


        // 裁剪图片中间部分
        if (this.data.imgInfo.width > 580 && this.data.imgInfo.height > 580 || this.data.imgInfo.width < 580 && this.data.imgInfo.height < 580) {
            if (dw > dh) {
                ctx.drawImage(logo, 0, (this.data.imgInfo.height - 580 / dw) / 2, this.data.imgInfo.width, 580 / dw, 30, 30, w / 750 * 580 * 2, w / 750 * 580 * 2)
            } else {
                ctx.drawImage(logo, (this.data.imgInfo.width - 580 / dh) / 2, 0, 580 / dh, this.data.imgInfo.height, 30, 30, w / 750 * 580 * 2, w / 750 * 580 * 2)
            }
        }
        // 拉伸图片
        else {
            if (this.data.imgInfo.width < 580) {
                ctx.drawImage(logo, 0, (this.data.imgInfo.height - 580 / dw) / 2, this.data.imgInfo.width, 580 / dw, 30, 30, w / 750 * 580 * 2, w / 750 * 580 * 2)
            } else {
                ctx.drawImage(logo, (this.data.imgInfo.width - 580 / dh) / 2, 0, 580 / dh, this.data.imgInfo.height, 30, 30, w / 750 * 580 * 2, w / 750 * 580 * 2)
            }
        }


        // 标签 
        ctx.drawImage(buyLogo, w / 750 * 30 * 2, w / 750 * 640 * 2, w / 750 * 88 * 2, w / 750 * 40 * 2)

        //绘制标题
        ctx.setTextAlign('left');
        ctx.setFillStyle('#151521'); //title文字颜色
        ctx.setFontSize(w / 750 * 28 * 2);
        // ctx.fillText(title, w / 750 * 32 * 2, w / 750 * 780 * 2);
        let canvasTitleArray = title.split("");
        let firstTitle = ""; //第一行字
        let secondTitle = ""; //第二行字
        for (let i = 0; i < canvasTitleArray.length; i++) {
            let element = canvasTitleArray[i];
            let firstWidth = ctx.measureText(firstTitle).width;
            //console.log(ctx.measureText(firstTitle).width);
            if (firstWidth > (w / 750 * 550 * 2)) {
                let secondWidth = ctx.measureText(secondTitle).width;
                //第二行字数超过，变为...
                if (secondWidth > (w / 750 * 550 * 2)) {
                    secondTitle += "...";
                    break;
                } else {
                    secondTitle += element;
                }
            } else {
                firstTitle += element;
            }
        }
        //第一行文字
        // ctx.fillText(firstTitle, 20, 278, 280) //绘制文本
        ctx.fillText(firstTitle, w / 750 * 28 * 2, w / 750 * 730 * 2);
        //第二行问题
        if (secondTitle) {
            // ctx.fillText(secondTitle, 20, 300, 280) //绘制文本
            ctx.fillText(secondTitle, w / 750 * 28 * 2, w / 730 * 758 * 2);
        }

        // 价格
        let price = this.data.sharePrice // 标题
        let num = this.data.shareNum // 标题
        ctx.setFontSize(w / 750 * 32 * 2)
        ctx.setFillStyle('#ff3b39');
        //绘制文本
        ctx.fillText(`${price?'￥'+price:''}    ${num?'库存'+num:''}`, w / 750 * 32 * 2, w / 750 * 860 * 2)

        ctx.drawImage(code, w / 750 * 30 * 2, w / 750 * 880 * 2, w / 750 * 580 * 2, w / 750 * 200 * 2)
        //绘制文本 

        ctx.draw(false, () => {
            //调用接口将画布转换为图片
            wx.canvasToTempFilePath({
                x: 0,
                y: 0,
                fileType: 'jpg',
                quality: 1,
                width: w / 750 * 640 * 2,
                height: w / 750 * 1080 * 2,
                destWidth: w / 750 * 640 * 2,
                destHeight: w / 750 * 1080 * 2,
                canvasId: 'shareFrends',
                success: res => {

                    wx.hideToast();

                    this.setData({
                        sharePicUrl: res.tempFilePath //生成的图片路径
                    }, () => {

                        //渲染完后再显示分享海报
                        this.setData({
                            share: false,
                            showSharePic: true
                        })

                    })
                },
                fail(err) {
                    wx.showToast({
                        title: '图片生成失败，请稍候再试！',
                        icon: 'none',
                        mask: true
                    })
                }
            })
        })
    },

    //获取头像
    getHead() {
        return new Promise((resolve, reject) => {
            wx.downloadFile({
                url: this.data._selData.headIcon,
                success: res => {
                    resolve(res.tempFilePath)
                }
            })
        })
    },

    //获取logo
    // this.data.shareTitle,  this.data.shareImg,
    getLogo() {
        return new Promise((resolve, reject) => {
            wx.downloadFile({
                // url: this.data._selData.logoUrl,
                url: this.data.shareImg,
                success: res => {
                    resolve(res.tempFilePath);
                },
                fail: (err) => {
                    console.log(er)
                }
            })
        })
    },

    //获取二维码
    getCode() {
        return new Promise((resolve, reject) => {
            let tid = this.data._selData.tid;

            wx.downloadFile({
                url: this.data._selData.codeLogo,
                success: res => {
                    resolve(res.tempFilePath);
                },
                fail: (err) => {
                    console.log(er)
                }
            })
        })
    },
    //获取buyLogo
    getBuyLogo() {
        return new Promise((resolve, reject) => {
            wx.downloadFile({
                url: this.data._selData.buyLogoUrl,
                success: res => {
                    resolve(res.tempFilePath);
                },
                fail: (err) => {
                    console.log(err)
                }
            })
        })
    },


    //关闭分享海报
    closeShare() {
        this.setData({
            showSharePic: false
        })
    },

    //保存图片
    savePic() {
        let sharePicUrl = this.data.sharePicUrl;
        wx.getSetting({
            success: res => {
                if (res.authSetting['scope.writePhotosAlbum'] == false) {
                    wx.showModal({
                        title: '提示',
                        content: '是否授权将图片保存到相册？',
                        confirmColor: '#2ca2ed',
                        success: res => {
                            //点击确定打开授权设置
                            if (res.confirm) {

                                wx.openSetting({
                                    success: res => {

                                        setTimeout(() => {
                                            if (res.authSetting['scope.writePhotosAlbum'] == true) {

                                                wx.saveImageToPhotosAlbum({
                                                    filePath: sharePicUrl,
                                                    success: res => {
                                                        this.closeShare();
                                                        wx.showToast({
                                                            title: '已成功保存到相册！',
                                                            icon: 'none',
                                                            duration: 3000,
                                                        })
                                                    },
                                                    fail: err => {
                                                        wx.showToast({
                                                            title: '保存失败！',
                                                            icon: 'none',
                                                            duration: 3000,
                                                        })
                                                    }
                                                })
                                            } else {
                                                wx.showToast({
                                                    title: '保存失败！',
                                                    icon: 'none',
                                                    duration: 3000,
                                                })
                                            }
                                        }, 500)
                                    }
                                })
                            }
                        }
                    })
                } else {

                    wx.saveImageToPhotosAlbum({
                        filePath: sharePicUrl,
                        success: res => {
                            this.closeShare();
                            wx.showToast({
                                title: '已成功保存到相册！',
                                icon: 'none',
                                duration: 3000,
                            })
                        }
                    })

                }
            }
        })

    },

})
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