小程序 uniapp 实现pdf 电子合同签名并导出功能

左手的ㄟ右手 2021-09-03 03:26 4159阅读 0赞

# 小程序 uniapp 实现pdf 电子合同签名 并导出功能 #

需求流程：

1.  用户只允许上传pdf
2.  后端将上传后的pdf以base64图片的形式返回
3.  用户设置签名的位置
4.  位置设置完成，将电子签名放到设定的位置处
5.  利用canvas将两张图片合成一张图片，保存至相册

实操  
![在这里插入图片描述][20201204143926880.gif_pic_center]

### 基本功能不再赘述，简要概括 ###

1：首先是新建签名，出现可缩放，拖拽的框，我是借鉴uniapp插件  
[插件地址： https://ext.dcloud.net.cn/plugin?id=2059][https_ext.dcloud.net.cn_plugin_id_2059]

2: 按照插件步骤执行完毕，下一步就是获取拖拽，缩放之后的 宽高和坐标  
x, y, w, h  
在下载的插件里面，有个end方法，在end方法里面，获取当前框的大小的位置

end(e) { 
          uni.setStorageSync("storage_x", parseInt(pdfX));
          uni.setStorageSync("storage_y", parseInt(pdfY));
          uni.setStorageSync("storage_w", parseInt(pdfW));
          uni.setStorageSync("storage_h", parseInt(pdfH));
          this.tempGraphArr = [];
    
          if (isMove) { 
            isMove = false; // 重置移动标识
            // 用户操作结束时记录历史
    
            this.recordHistory();
          }
        },

记录之后，画框，旋转，缩放，这一快就结束了。之后就是  
写签名  
将签名放在指定位置  
将签名导出本地

#### 写签名直接复制过去就能用 ####

##### 画完之后，调用uni.canvasToTempFilePath ,会返回一个本地路径，并将本地路劲传到之前选择框的页面 #####

<template>
      
      <div class="contain">
        <canvas
          canvas-id="mycanvas"
          class="mycanvas"
          disable-scroll="true"
          @touchstart="ontouchstart"
          @touchmove="touchmove"
          @touchend="touchend"
        ></canvas>
        <view class="footer">
          <view class="footer-wrap">
            <pdf-button
              text="清除"
              mode="clear"
              @pdfButton="clear"
              class="btn"
            ></pdf-button>
    
            <pdf-button
              v-if="show"
              text="完成"
              mode="pdfGary"
              left="31rpx"
              class="btn"
            >
            </pdf-button>
            <pdf-button
              v-else
              text="完成"
              mode="pdfFinssh"
              @pdfButton="close"
              left="31rpx"
              class="btn"
            >
            </pdf-button>
          </view>
        </view>
      </div>
    </template>
    
    <script>
    import pdfButton from "../../components/pdfButton";
    
    
    export default { 
      components: { 
        pdfButton,
      },
      data() { 
        return { 
          headerStyleHeight: 0,
          headerStyleTop: 0,
          oc: "",
          points: [], //路径点集合
          showCanvas: false, //
          show: true,
        };
      },
      mounted() { 
        this.clear();
      },
      onShow() { 
        this.initCanvas();
        // console.log('参数',+uni.getStorageSync("storage_w"));
      },
      methods: { 
        close() { 
          uni.canvasToTempFilePath({ 
            canvasId: "mycanvas",
            success: (res) => { 
              console.log("res", res.tempFilePath);
              const canvas = res.tempFilePath;
              uni.navigateTo({ 
                url: `/pages/previewFinally/index?hasSingle=${ 1}&canvas=${ canvas}`,
              });
            },
          });
        },
    
        initCanvas() { 
          this.showCanvas = true;
          this.oc = uni.createCanvasContext("mycanvas");
          //设置画笔样式
          this.oc.lineWidth = 4;
          this.oc.lineCap = "round";
          this.oc.lineJoin = "round";
          this.oc.strokeStyle = "black";
          this.oc.fillStyle = "#fff";
          this.oc.lineWidth = 5;
          this.oc.fillRect(0, 0, 400, 700);
          this.oc.fill();
          this.oc.draw();
        },
        ontouchend(e) { 
          console.log("结束啊啊啊啊");
          oc.ontouchmove = null;
          this.show = false;
        },
        ontouchmove(e) { 
          const {  clientX, clientY } = e.changedTouches[0];
          oc.lineTo(clientX - oc.offsetLeft, clientY - oc.offsetTop);
          oc.stroke();
        },
        //触摸开始，获取到起点
    
        ontouchstart(e) { 
          // debugger
          // ctx.beginPath();
          const startX = e.changedTouches[0].x;
          const startY = e.changedTouches[0].y;
    
          let startPoint = { 
            X: startX,
            Y: startY,
          };
          this.points.push(startPoint);
          //每次触摸开始，开启新的路径
          this.oc.beginPath();
        },
        //触摸移动，获取到路径点
        touchmove(e) { 
          let moveX = e.changedTouches[0].x;
          let moveY = e.changedTouches[0].y;
          let movePoint = { 
            X: moveX,
            Y: moveY,
          };
          this.points.push(movePoint); //存点
          let len = this.points.length;
          if (len >= 2) { 
            this.draw(); //绘制路径
          }
        },
    
        // 触摸结束，将未绘制的点清空防止对后续路径产生干扰
        touchend() { 
          this.points = [];
          this.show = false;
        },
    
        /* *********************************************** # 绘制笔迹 # 1.为保证笔迹实时显示，必须在移动的同时绘制笔迹 # 2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo) # 3.将上一次的终点作为下一次绘制的起点（即清除第一个点） ************************************************ */
        draw() { 
          let point1 = this.points[0];
          let point2 = this.points[1];
          this.points.shift();
          this.oc.moveTo(point1.X, point1.Y);
          this.oc.lineTo(point2.X, point2.Y);
          this.oc.stroke();
          this.oc.draw(true);
        },
        //清空画布
        clear() { 
          this.show = true;
          let that = this;
          uni.getSystemInfo({ 
            success: (res) => { 
              let canvasw = res.windowWidth;
              let canvash = res.windowHeight;
              that.oc.clearRect(0, 0, canvasw, canvash);
              that.oc.draw(true);
              // that.initCanvas();
            },
          });
        },
      },
    };
    </script>
    
    <style lang="scss">
    .contain { 
      height: 100vh;
      position: relative;
      .button { 
        width: 100%;
        height: 50px;
        line-height: 50px;
        text-align: center;
        font-size: 20px;
        border: 1px solid #bbbbbb;
      }
    
      .header-box { 
        width: 100%;
        background-color: #ffffff;
        padding-bottom: 20rpx;
        color: red;
      }
    
      .content-box { 
        width: 100%;
        height: 500px;
        // background-color: aliceblue;
        padding: 20rpx;
        box-sizing: border-box;
      }
    
      .signature { 
        position: fixed;
        top: 10px;
        left: 2%;
        z-index: 999;
        width: 96%;
      }
    
      .mycanvas { 
        width: 100%;
        height: 330rpx;
      }
    
      .footer { 
        font-size: 14px;
        height: 100%;
        display: flex;
        justify-content: space-around;
        align-items: center;
        background: #f2f3f5;
        .footer-wrap { 
          height: 100%;
          padding: 57rpx 37rpx 17rpx 37rpx;
          box-sizing: border-box;
          display: flex;
          align-items: center;
        }
      }
      .sty-single { 
        position: absolute;
        top: 70rpx;
        left: 0rpx;
        width: 569rpx;
        height: 200rpx;
        z-index: 111;
      }
    }
    .btn { 
      height: 100%;
    }
    </style>

#### 在之前设置位置的页面，将画好的签名。放到指定位置 ####

// 接收传来的canvas
    
    onLoad(options) { 
        this.hasSingle = options.hasSingle;
        this.canvas = options.canvas;
        this.px();
      },
      // 渲染canvas，注意宽高，坐标。用之前保存的坐标
      data() { 
        return { 
          pdfDataList: uni.getStorageSync("filePath"),
          hasSingle: 0,
          canvas: "",
          rpx: "",
          finillyX: uni.getStorageSync("storage_x"),
          finillyY: uni.getStorageSync("storage_y"),
          finillyW: uni.getStorageSync("storage_w"),
          finillyH: uni.getStorageSync("storage_h"),
        };
      },
     // 渲染
     <image
            v-if="pdfDataList != '' && hasSingle == 1"
            :src="canvas"
            class="sty-single transfo"
            :style="{ 
              width: finillyW + 'px',
              height: finillyH + 'px',
              top: finillyY + 'px',
              left: finillyX + 'px',
            }"
          ></image>

### 合成图片，将两个图片都画成canvas，然后利用API导出 ###

###### 结构 ######

###### 功能 ######

finishSave() { 
          // 提示用户正在合成，否则用户可能有不当操作或者以为手机卡死
          wx.showLoading({ 
            title: "合成中",
            mask: true,
          });
          // 创建画布对象
          const ctx = uni.createCanvasContext("myCanvas");
          console.log("ctx", ctx);
          // 获取图片信息，要按照原图来绘制，否则图片会变形
          uni.getImageInfo({ 
            src: this.pdfDataList, // 底图
            success: (res) => { 
              // 根据 图片的大小 绘制底图 的大小
              console.log(" 底图", res);
              let imgPath = res.path;
              ctx.drawImage(
                imgPath,
                0,
                0,
                (750 / 2) * this.rpx,
                (1061 / 2) * this.rpx
              );
              wx.getImageInfo({ 
                src: this.canvas,
                success: (res) => { 
                  console.log(" 签名", res);
                  ctx.drawImage(
                    res.path,
                    this.finillyX,
                    this.finillyY,
                    this.finillyW,
                    this.finillyH
                  );
                  ctx.draw();
                  setTimeout(() => { 
                    console.log("111");
                    uni.canvasToTempFilePath({ 
                      canvasId: "myCanvas",
                      success: (res) => { 
                        uni.hideLoading();
                        console.log("合成图片", res);
                        const tempFilePath = res.tempFilePath;
                        // 保存到相册
                        wx.saveImageToPhotosAlbum({ 
                          filePath: tempFilePath,
                          success: (res) => { 
                            // 修改下载状态
                            wx.showModal({ 
                              title: "温馨提示",
                              content: "已保存到本地相册",
                              confirmText: "我知道了",
                              showCancel: false,
                              success: (res) => { 
                                console.log("res图片保存成功", res);
                                if (res.confirm) { 
                                  uni.reLaunch({ 
                                    url: "/pages/contract/index",
                                  });
                                }
                                uni.setStorageSync("sing", "");
                                uni.setStorageSync("File", "");
                                uni.setStorageSync("filePath", "");
                              },
                            });
                          },
                        });
                      },
                    });
                  }, 2000);
                },
              });
            },
          });
        },

由于canvas画出来的坐标都是px,所以在保存的时候。为了不同机型，需要做适配，按比例就好

px() { 
          const {  windowWidth } = wx.getSystemInfoSync();
          this.rpx = windowWidth / 375;
          //获取屏幕宽度，获取自适应单位
          console.log("rpx", this.rpx);
        },

# 以上代码仅供参考，出现v-if 判断，或者pdf-button之类的。改成自己需要即可 #

[20201204143926880.gif_pic_center]: /images/20210813/7812083cccc3438ca5c649b51ec6cdf8.png
[https_ext.dcloud.net.cn_plugin_id_2059]: https://ext.dcloud.net.cn/plugin?id=2059