前端实现签字效果+合同展示

LiuPing_Xie2024-08-16 19:47

要做一个这样的功能，后端返回一个合同的整体html，前端进行签字，以下是一些重要思路！

获取一个高度会变的元素的高度

script 代码

javascript 复制代码 
let bigBoxHeight = ref(0);
// 获取到元素
let bigBox = document.querySelector(".bigBox");
// 设置高度为 auto
bigBox.style.height = "auto";
// 获取 offsetHeight
const height = bigBox.offsetHeight;
// 设置值
bigBoxHeight.value = height;

注： offsetHeight：返回一个元素的高度，包括其padding和border，但不包括其margin。

template 代码

html 复制代码 
<div class="bigBox" :style="{ height: bigBoxHeight + 'px' }">
  <div class="contractBox">
    <div v-html="printData"></div>
  </div>
  <!-- 遮罩层，返回的printData里设置了可编辑，但是这里只是展示用，且修改了也不会有影响，所以就简单的加个遮罩就行了 -->
  <div class="markBox" :style="{ height: bigBoxHeight + 'px' }"></div>
</div>

获取元素设置的 transform

感谢：原生js获取元素transform的scale和rotate

javascript 复制代码 
// 获取设置了transform的元素
let contractBox = document.querySelector(".contractBox");
// 获取浏览器计算后的结果
let st = window.getComputedStyle(contractBox, null);
// 从结算后的结果中找到 transform，也可以直接 st.transform
var tr = st.getPropertyValue("transform");
if (tr === "none") {
  // 为none表示未设置
  bigBox.style.height = "auto";
  const height = bigBox.offsetHeight + 50;
  bigBoxHeight.value = height;
} else {
  bigBox.style.height = "auto";
  // 缩放需要 * 缩放比例 + 边距（margin/padding）
  const height = bigBox.offsetHeight * 0.5 + 50;
  bigBoxHeight.value = height;
}

适配手机

上面设置transform是因为返回的html文档不是那么的自适应，所以菜鸟就在手机端，让其渲染700px，但是再缩小0.5倍去展示，即可解决！

css 代码

css 复制代码 
@media screen and (max-width: 690px) {
  .contractBox {
    width: 700px !important;
    transform: scale(0.5);
    // 防止延中心点缩放而导致上面留白很多（合同很长，7000px左右）
    transform-origin: 5% 0;
  }
}

.bigBox {
  position: relative;
  // 设置是因为 scale 缩放了但是元素还是占本身那么大，所以要超出隐藏
  overflow: hidden;
  .markBox {
    width: 100%;
    position: absolute;
    left: 0;
    bottom: 0;
    top: 0;
    bottom: 0;
  }
}
.contractBox {
  width: 70%;
  margin: 50px auto 0px;
  overflow: hidden;
}

transform-origin: 5% 0; 的原因

这里设置 5% 是为了居中，因为这里有个问题就是不能设置bigBox为display：flex，不然里面的内容就是按照width：100%然后缩放0.5，而不是width：700px来缩放的！

是flex搞的鬼，菜鸟这里就用了个简单办法。

其实正统做法应该是获取宽度，再用窗口宽度减去获取的宽度 / 2，然后通过该值设置margin！

修改后

菜鸟既然想到了上面的居中方式，那就直接实现了，这里给上代码！

script 代码

javascript 复制代码 
// 是否缩放，来确定margin-left取值
let isScale = ref(false);
let bigBoxmargin = ref(0);

let bigBox = document.querySelector(".bigBox");
let contractBox = document.querySelector(".contractBox");
let st = window.getComputedStyle(contractBox, null);
var tr = st.getPropertyValue("transform");
if (tr === "none") {
  isScale.value = false;
  bigBox.style.height = "auto";
  const height = bigBox.offsetHeight + 50;
  bigBoxHeight.value = height;
} else {
  isScale.value = true;
  bigBox.style.height = "auto";
  // 缩放需要 * 缩放比例 + 边距（margin/padding）
  const height = bigBox.offsetHeight * 0.5 + 50;
  // 不用 st.witdh 是因为 st.witdh 获取的值是 700px，不能直接运算，这里菜鸟就偷懒了，不想处理了
  bigBoxmargin.value = (window.innerWidth - 700 * 0.5) / 2;
  bigBoxHeight.value = height;
}

template 代码

html 复制代码 
<div class="bigBox" :style="{ height: bigBoxHeight + 'px' }">
  <div class="contractBox" :style="{ marginLeft: isScale ? bigBoxmargin + 'px' : 'auto' }">
    <div v-html="printData"></div>
  </div>
  <div class="markBox" :style="{ height: bigBoxHeight + 'px' }"></div>
</div>

签字效果

这里签字效果，菜鸟是使用 el-dialog 实现的，el-dialog 的使用方式见：element plus 使用细节

这里主要粘贴签字的代码

html 复制代码 
<script setup>
import { ref, onMounted, nextTick } from "vue";

// eslint-disable-next-line
const props = defineProps({
  dialogVisible: {
    type: Boolean,
    default: false,
  },
});

// eslint-disable-next-line
const emit = defineEmits(["closeEvent"]);

// 关闭弹窗
function handleClose() {
  emit("closeEvent", false);
  // 解除禁止页面滚动
  document.body.removeEventListener("touchmove", preventDefault);
}
const dialogBox = ref();
function closeDialog() {
  dialogBox.value.resetFields();
}

// 禁止页面滚动
function preventDefault(e) {
  e.preventDefault();
}
document.body.addEventListener("touchmove", preventDefault, { passive: false });

// 签名
// 配置内容
const config = {
  width: window.innerWidth, // 宽度
  height: window.innerHeight - 300, // 高度，减300是为了给dialog的footer一点空间显示
  lineWidth: 5, // 线宽
  strokeStyle: "red", // 线条颜色
  lineCap: "round", // 设置线条两端圆角
  lineJoin: "round", // 线条交汇处圆角
};

let canvas = null;
let ctx = null;
onMounted(async () => {
  await nextTick();
  // 获取canvas 实例
  canvas = document.querySelector(".canvas");
  // 设置宽高
  canvas.width = config.width;
  canvas.height = config.height;
  // 设置一个边框
  canvas.style.border = "1px solid #000";
  // 创建上下文
  ctx = canvas.getContext("2d");

  // 设置填充背景色
  ctx.fillStyle = "transparent";
  // 绘制填充矩形
  ctx.fillRect(
    0, // x 轴起始绘制位置
    0, // y 轴起始绘制位置
    config.width, // 宽度
    config.height // 高度
  );
});

// 保存上次绘制的 坐标及偏移量
const client = {
  offsetX: 0, // 偏移量
  offsetY: 0,
  endX: 0, // 坐标
  endY: 0,
};

// 判断是否为移动端
const mobileStatus = /Mobile|Android|iPhone/i.test(navigator.userAgent);

// 初始化
const init = (event) => {
  // 获取偏移量及坐标
  const { offsetX, offsetY, pageX, pageY } = mobileStatus ? event.changedTouches[0] : event;

  // 修改上次的偏移量及坐标
  client.offsetX = offsetX;
  client.offsetY = offsetY;
  client.endX = pageX;
  client.endY = pageY;

  // 清除以上一次 beginPath 之后的所有路径，进行绘制
  ctx.beginPath();
  // 根据配置文件设置相应配置
  ctx.lineWidth = config.lineWidth;
  ctx.strokeStyle = config.strokeStyle;
  ctx.lineCap = config.lineCap;
  ctx.lineJoin = config.lineJoin;
  // 设置画线起始点位
  ctx.moveTo(client.endX, client.endY);
  // 监听 鼠标移动或手势移动
  window.addEventListener(mobileStatus ? "touchmove" : "mousemove", draw);
};
// 绘制
const draw = (event) => {
  console.log(event);
  // 获取当前坐标点位
  const { pageX, pageY } = mobileStatus ? event.changedTouches[0] : event;
  // 超出范围不监听
  if (pageY > config.height) {
    return;
  }
  // 修改最后一次绘制的坐标点
  client.endX = pageX;
  client.endY = pageY;

  // 根据坐标点位移动添加线条
  ctx.lineTo(pageX, pageY);

  // 绘制
  ctx.stroke();
};
// 结束绘制
const cloaseDraw = () => {
  // 结束绘制
  ctx.closePath();
  // 移除鼠标移动或手势移动监听器
  window.removeEventListener("mousemove", draw);
};
// 创建鼠标/手势按下监听器
window.addEventListener(mobileStatus ? "touchstart" : "mousedown", init);
// 创建鼠标/手势 弹起/离开 监听器
window.addEventListener(mobileStatus ? "touchend" : "mouseup", cloaseDraw);

// 取消-清空画布
const cancel = () => {
  // 清空当前画布上的所有绘制内容
  ctx.clearRect(0, 0, config.width, config.height);
};
// 保存-将画布内容保存为图片
const save = () => {
  // 将canvas上的内容转成blob流
  canvas.toBlob((blob) => {
    // 获取当前时间并转成字符串，用来当做文件名
    const date = Date.now().toString();
    // 创建一个 a 标签
    const a = document.createElement("a");
    // 设置 a 标签的下载文件名
    a.download = `${date}.png`;
    // 设置 a 标签的跳转路径为 文件流地址
    a.href = URL.createObjectURL(blob);
    // 手动触发 a 标签的点击事件
    a.click();
    // 移除 a 标签
    a.remove();
  });
  handleClose();
};
</script>

<template>
  <div>
    <el-dialog
      title="签字"
      ref="dialogBox"
      :modelValue="dialogVisible"
      :before-close="handleClose"
      @close="closeDialog"
      :close-on-click-modal="false"
      :destroy-on-close="true"
      top="0"
      width="100%"
    >
      <canvas class="canvas"></canvas>
      <template #footer>
        <div>
          <el-button type="primary" @click="save">保存</el-button>
          <el-button @click="cancel">清除</el-button>
          <el-button @click="handleClose">关闭</el-button>
        </div>
      </template>
    </el-dialog>
  </div>
</template>

<style lang="scss">
.el-dialog__header {
  display: none;
}
.el-dialog__body {
  padding: 0 !important;
}
</style>

取消el-dialog的头部+边距

因为这里的 client 设置的偏移量都是 0，菜鸟不会改（感觉应该加上el-dialog的头部+边框的偏移量），如果不取消的话，就是错位着写的！

为什么禁止界面滚动

这里禁止是因为手机端，签名时写 "竖" 操作时，容易触发下拉整个界面的事件！导致写字中断，体验感极差，所以弹窗弹出时阻止事件，关闭后移除！

这里函数 preventDefault 必须提出，不然会取消不掉！

vue3 使用 nextTick

获取元素必须在 onMounted 中，但是 el-dialog 即使写在 onMounted 里面也不行，需要加上 nextTick ！

实现效果

签字判断是横是竖

今天菜鸟又遇见了大麻烦，就是这个签字不能知道别人是横屏横着写的还是竖屏横着写的，eg：

菜鸟的思路就是获取到签字部分，然后如果横着签字就直接截取那部分设置样式，如果竖着签字就设置样式旋转 -90deg，那如何获取签字部分的大小呢？

canvas 去掉空白部分

canvas 去掉空白部分

修改上面 save 中代码

javascript 复制代码 
const save = () => {
	// 将canvas上的内容转成blob流
	var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height).data;
	var lOffset = canvas.width,
	  rOffset = 0,
	  tOffset = canvas.height,
	  bOffset = 0;
	
	for (var i = 0; i < canvas.width; i++) {
	  for (var j = 0; j < canvas.height; j++) {
	    var pos = (i + canvas.width * j) * 4;
	    if (imgData[pos] > 0 || imgData[pos + 1] > 0 || imgData[pos + 2] || imgData[pos + 3] > 0) {
	      // 说第j行第i列的像素不是透明的
	      // 楼主貌似底图是有背景色的,所以具体判断RGBA的值可以根据是否等于背景色的值来判断
	      bOffset = Math.max(j, bOffset); // 找到有色彩的最底部的纵坐标
	      rOffset = Math.max(i, rOffset); // 找到有色彩的最右端
	
	      tOffset = Math.min(j, tOffset); // 找到有色彩的最上端
	      lOffset = Math.min(i, lOffset); // 找到有色彩的最左端
	    }
	  }
	}
}

canvas.getContext('2d').getImageData(0, 0, 宽, 高) 会返回一个当前 canvas 的图像数据对象，其中有一个data属性，是一个一维数组,这个一维数组，每4个下标分别代表了一个像素点的 R,G,B,A 的值，只需要遍历这些值就能找到边界了。

感谢：canvas 裁剪空白区域

canvas裁剪图片

canvas裁剪图片

但是获取到了区域并不行，因为我还需要将其截取，然后转成图片传给后端，且还要让后端知道到底是横着放 html 模板里还是竖着放，思来想去，感觉直接返回 base64 的 img 元素给后端更好，因为我就可以直接设置style，后端只需要放到对应的地方就行，所以save继续修改为

javascript 复制代码 
const save = () => {
  // 将canvas上的内容转成blob流
  var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height).data;
  var lOffset = canvas.width,
    rOffset = 0,
    tOffset = canvas.height,
    bOffset = 0;

  for (var i = 0; i < canvas.width; i++) {
    for (var j = 0; j < canvas.height; j++) {
      var pos = (i + canvas.width * j) * 4;
      if (imgData[pos] > 0 || imgData[pos + 1] > 0 || imgData[pos + 2] || imgData[pos + 3] > 0) {
        // 说第j行第i列的像素不是透明的
        // 楼主貌似底图是有背景色的,所以具体判断RGBA的值可以根据是否等于背景色的值来判断
        bOffset = Math.max(j, bOffset); // 找到有色彩的最底部的纵坐标
        rOffset = Math.max(i, rOffset); // 找到有色彩的最右端

        tOffset = Math.min(j, tOffset); // 找到有色彩的最上端
        lOffset = Math.min(i, lOffset); // 找到有色彩的最左端
      }
    }
  }

  // 重新创建一个canvas，将之前的canvas上的图片，按照获取到的大小去截取
  const trimmedWidth = rOffset - lOffset + 1;
  const trimmedHeight = bOffset - tOffset + 1;
  const trimmedCanvas = document.createElement("canvas");
  trimmedCanvas.width = trimmedWidth;
  trimmedCanvas.height = trimmedHeight;
  const trimmedContext = trimmedCanvas.getContext("2d");
  trimmedContext.putImageData(
    ctx.getImageData(lOffset, tOffset, trimmedWidth, trimmedHeight),
    0,
    0
  );
  
  // 将截取后的生成图片，并设置样式
  console.log(trimmedWidth);
  console.log(trimmedHeight);
  var newUrl = trimmedCanvas.toDataURL();
  var newImage = new Image();
  newImage.src = newUrl;
  console.log(trimmedWidth < trimmedHeight);
  if (trimmedWidth < trimmedHeight) {
    newImage.style.height = "100px";
    newImage.style.transform = "rotate(-" + 90 + "deg)";
  } else {
    newImage.style.width = "100px";
  }

  console.log(newImage);

  handleClose();
};

newImage 打印出来是一个元素：

html 复制代码 
<img 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" style="transform: rotate(-90deg);">

至此算是完成了整个签字功能！

最终完善代码，可以直接使用

其实这里还有一个问题，就是不知道横屏后的用户到底是哪边横屏，可能要旋转-90deg，也可能是正90deg，这里菜鸟想的是一个简单办法，就是给个示例文字，让用户根据示例文字进行签字！

template

html 复制代码 
<template>
  <div>
    <el-dialog
      title="签字"
      ref="dialogBox"
      :modelValue="dialogVisible"
      :before-close="handleClose"
      @close="closeDialog"
      :close-on-click-modal="false"
      :destroy-on-close="true"
      top="0"
      width="100%"
    >
      <div class="canvasBox" :style="{ height: config.height + 'px' }">
        <canvas class="canvas"></canvas>
        <div class="tipTxt" v-show="showTip">
          <p>示例文字！</p>
          <p class="redTxt">请按示例文字方向，正楷清晰书写。谢谢！</p>
        </div>
      </div>
      <template #footer>
        <div>
          <el-button type="primary" @click="save">保存</el-button>
          <el-button @click="cancel">清除</el-button>
          <el-button @click="handleClose(false)">关闭</el-button>
        </div>
      </template>
    </el-dialog>
  </div>
</template>

<style lang="scss">
.el-dialog__header {
  display: none;
}
.el-dialog__body {
  padding: 0 !important;
}
.canvasBox {
  position: relative;
}
.canvas,
.tipTxt {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
}
.tipTxt {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}
.tipTxt p {
  color: #999;
  font-size: 80px;
}
.tipTxt .redTxt {
  color: rgba(255, 0, 0, 0.5);
  font-size: 50px;
}

@media screen and (max-width: 690px) {
  .tipTxt {
    transform: rotate(90deg);
  }
  .tipTxt p {
    font-size: 50px;
  }
  .tipTxt .redTxt {
    font-size: 18px;
  }
}
</style>

js 控制 showTip 的展示

javascript 复制代码 
<script setup>
import { ref, onMounted, nextTick } from "vue";

// eslint-disable-next-line
const props = defineProps({
  dialogVisible: {
    type: Boolean,
    default: false,
  },
});

// eslint-disable-next-line
const emit = defineEmits(["closeEvent"]);

// 关闭弹窗
function handleClose(imgEl) {
  console.log(imgEl);
  emit("closeEvent", imgEl);
  // 禁止页面滚动
  document.body.removeEventListener("touchmove", preventDefault);
}
const dialogBox = ref();
function closeDialog() {
  dialogBox.value.resetFields();
}

// 禁止页面滚动
function preventDefault(e) {
  e.preventDefault();
}
document.body.addEventListener("touchmove", preventDefault, { passive: false });

// 签名
// 配置内容
const config = {
  width: window.innerWidth, // 宽度
  height: window.innerHeight - 150, // 高度
  lineWidth: 5, // 线宽
  strokeStyle: "red", // 线条颜色
  lineCap: "round", // 设置线条两端圆角
  lineJoin: "round", // 线条交汇处圆角
};

let canvas = null;
let ctx = null;
onMounted(async () => {
  await nextTick();
  // 获取canvas 实例
  canvas = document.querySelector(".canvas");
  console.log(canvas);
  // 设置宽高
  canvas.width = config.width;
  canvas.height = config.height;
  // 设置一个边框
  canvas.style.border = "1px solid #000";
  // 创建上下文
  ctx = canvas.getContext("2d");

  // 设置填充背景色
  ctx.fillStyle = "transparent";
  // 绘制填充矩形
  ctx.fillRect(
    0, // x 轴起始绘制位置
    0, // y 轴起始绘制位置
    config.width, // 宽度
    config.height // 高度
  );
});

// 保存上次绘制的 坐标及偏移量
const client = {
  offsetX: 0, // 偏移量
  offsetY: 0,
  endX: 0, // 坐标
  endY: 0,
};

// 判断是否为移动端
const mobileStatus = /Mobile|Android|iPhone/i.test(navigator.userAgent);

// 初始化
const init = (event) => {
  // 获取偏移量及坐标
  const { offsetX, offsetY, pageX, pageY } = mobileStatus ? event.changedTouches[0] : event;

  // 修改上次的偏移量及坐标
  client.offsetX = offsetX;
  client.offsetY = offsetY;
  client.endX = pageX;
  client.endY = pageY;

  // 清除以上一次 beginPath 之后的所有路径，进行绘制
  ctx.beginPath();
  // 根据配置文件设置相应配置
  ctx.lineWidth = config.lineWidth;
  ctx.strokeStyle = config.strokeStyle;
  ctx.lineCap = config.lineCap;
  ctx.lineJoin = config.lineJoin;
  // 设置画线起始点位
  ctx.moveTo(client.endX, client.endY);
  // 监听 鼠标移动或手势移动
  window.addEventListener(mobileStatus ? "touchmove" : "mousemove", draw);
};
// 绘制
const draw = (event) => {
  showTip.value = false;
  // 获取当前坐标点位
  const { pageX, pageY } = mobileStatus ? event.changedTouches[0] : event;
  // 修改最后一次绘制的坐标点
  client.endX = pageX;
  client.endY = pageY;

  // 根据坐标点位移动添加线条
  ctx.lineTo(pageX, pageY);

  // 绘制
  ctx.stroke();
};
// 结束绘制
const cloaseDraw = () => {
  // 结束绘制
  ctx.closePath();
  // 移除鼠标移动或手势移动监听器
  window.removeEventListener("mousemove", draw);
};
// 创建鼠标/手势按下监听器
window.addEventListener(mobileStatus ? "touchstart" : "mousedown", init);
// 创建鼠标/手势 弹起/离开 监听器
window.addEventListener(mobileStatus ? "touchend" : "mouseup", cloaseDraw);

// 取消-清空画布
const cancel = () => {
  // 清空当前画布上的所有绘制内容
  ctx.clearRect(0, 0, config.width, config.height);
  showTip.value = true;
};
// 保存-将画布内容保存为图片
const save = () => {
  // 将canvas上的内容转成blob流
  var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height).data;
  var lOffset = canvas.width,
    rOffset = 0,
    tOffset = canvas.height,
    bOffset = 0;

  for (var i = 0; i < canvas.width; i++) {
    for (var j = 0; j < canvas.height; j++) {
      var pos = (i + canvas.width * j) * 4;
      if (imgData[pos] > 0 || imgData[pos + 1] > 0 || imgData[pos + 2] || imgData[pos + 3] > 0) {
        // 说第j行第i列的像素不是透明的
        // 楼主貌似底图是有背景色的,所以具体判断RGBA的值可以根据是否等于背景色的值来判断
        bOffset = Math.max(j, bOffset); // 找到有色彩的最底部的纵坐标
        rOffset = Math.max(i, rOffset); // 找到有色彩的最右端

        tOffset = Math.min(j, tOffset); // 找到有色彩的最上端
        lOffset = Math.min(i, lOffset); // 找到有色彩的最左端
      }
    }
  }

  if (lOffset === config.width && rOffset === 0 && tOffset === config.height && bOffset === 0) {
    // eslint-disable-next-line
    ElMessage({
      message: "请签名后保存！",
      type: "warning",
    });
    return;
  }

  const trimmedWidth = rOffset - lOffset + 1;
  const trimmedHeight = bOffset - tOffset + 1;
  const trimmedCanvas = document.createElement("canvas");
  trimmedCanvas.width = trimmedWidth;
  trimmedCanvas.height = trimmedHeight;
  const trimmedContext = trimmedCanvas.getContext("2d");
  trimmedContext.putImageData(
    ctx.getImageData(lOffset, tOffset, trimmedWidth, trimmedHeight),
    0,
    0
  );

  const newUrl = trimmedCanvas.toDataURL();
  const newImage = new Image();
  newImage.src = newUrl;
  console.log(trimmedWidth < trimmedHeight);
  if (trimmedWidth < trimmedHeight) {
    newImage.style.height = "100px";
    newImage.style.transform = "rotate(-" + 90 + "deg)";
  } else {
    newImage.style.width = "100px";
  }
  // console.log(newImage.outerHTML + "</img>");

  handleClose(newImage.outerHTML + "</img>");
};

// 示例文字
let showTip = ref(true);
</script>

实现效果：

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