使用Vue3封装实现支持Base64导出的电子签名组件

<template>
	<!-- 签名容器 -->
	<div class="sign-container" >
		<div class="sign-preview" :class="[sizeClass, { 'has-sign': base64Img }]" @click="openDialog">
			<img v-if="base64Img" :src="base64Img" class="preview-image" />
			<div v-else class="placeholder">
				<el-icon><EditPen /></el-icon>
				<span>点击签名</span>
			</div>
		</div>

		<!-- 签字弹窗 -->
		<el-dialog v-model="dialogVisible" title="电子签名" width="800px">
			<vue-esign ref="esignRef" :width="800" :height="300" :lineWidth="4" :lineColor="'#000000'" :bgColor="'#ffffff'"  :id="uuid" />

			<template #footer>
				<el-button @click="dialogVisible = false">取消</el-button>
				<el-button @click="handleReset">清空</el-button>
				<el-button type="primary" @click="handleConfirm">确认</el-button>
			</template>
		</el-dialog>
	</div>
</template>
 
<script setup>
import { ref } from 'vue';
import { useMessage, useMessageBox } from '/@/hooks/message';
import { generateUUID } from '/@/utils/other';

import vueEsign from 'vue-esign';

// 生成组件唯一id
const uuid = ref('id-' + generateUUID());
// 组件尺寸
const sizeClass = computed(() => `sign-size--${props.size}`);

const emit = defineEmits(['update:modelValue']);
const props = defineProps({
	modelValue: String, // v-model绑定
    disabled: {
		type: Boolean,
		default: false,
	},
	size: {
		type: String,
		default: 'default',
		validator: (v) => ['small', 'default', 'large'].includes(v),
	},
});

const dialogVisible = ref(false);
const esignRef = ref(null);
const base64Img = ref(props.modelValue);

// 打开弹窗时重置画布
const openDialog = () => {
    if (props.disabled) return;
	dialogVisible.value = true;
	// handleReset();
};

// 清空画布（保留二次确认）
const handleReset = async () => {
	try {
		await useMessageBox().confirm('此操作将清空签名，确定吗？');
		esignRef.value?.reset();
	} catch {}
};
// 生成签名后压缩
const compressBase64 = (base64) => {
	return new Promise((resolve, reject) => {
		const img = new Image();
		img.src = base64;

		img.onload = () => {
			// 创建canvas并设置缩放尺寸
			const canvas = document.createElement('canvas');
			const ctx = canvas.getContext('2d');

			// 计算压缩后尺寸（取原图50%）
			const targetWidth = img.width * 0.5;
			const targetHeight = img.height * 0.5;

			// 设置画布尺寸
			canvas.width = targetWidth;
			canvas.height = targetHeight;

			// 绘制压缩图像
			ctx.drawImage(img, 0, 0, targetWidth, targetHeight);

			// 生成新base64（自动处理格式）
			const mimeType = base64.match(/data:(.*?);/)[1];
			canvas.toBlob(
				(blob) => {
					const reader = new FileReader();
					reader.onloadend = () => resolve(reader.result);
					reader.readAsDataURL(blob);
				},
				mimeType,
				0.6
			); // 质量参数生效于JPEG/WebP格式
		};

		img.onerror = (e) => reject('图片加载失败');
	});
};
// 确认签名
const handleConfirm = async () => {
	esignRef.value
		.generate()
		.then(async (res) => {
			base64Img.value = await compressBase64(res);
			// 验证压缩效果
			const originalSize = Math.round((res.length * 3) / 4 / 1024);
			const compressedSize = Math.round((base64Img.value.length * 3) / 4 / 1024);
			console.log(` 尺寸变化：${originalSize}KB → ${compressedSize}KB`);
			emit('update:modelValue', base64Img.value);
			dialogVisible.value = false;
		})
		.catch(() => {
			base64Img.value = '';
			emit('update:modelValue', '');
			dialogVisible.value = false;
		});
};


// watch同步
watch(
	() => props.modelValue,
	async (val) => {
		if (!val) {
			base64Img.value = '';
			esignRef.value?.reset();
		}
		console.log(val);
        base64Img.value = await compressBase64(val);

	}
);



onBeforeUnmount(() => {
	// 释放canvas内存
	const canvas = esignRef.value?.$el.querySelector('canvas');
	canvas.width = 0;
	canvas.height = 0;
	URL.revokeObjectURL(base64Img.value); // 释放Blob URL
});
</script>
 
<style scoped lang="scss">
.sign-container {
	display: inline-block;
	cursor: pointer;
}
.sign-preview {
	border: 1px solid #dcdfe6;
	background: #fff;
	border-radius: 4px;

	&.sign-size--small {
		width: 120px;
		height: 60px;
	}
	&.sign-size--default {
		width: 180px;
		height: 90px;
	}
	&.sign-size--large {
		width: 240px;
		height: 120px;
	}

	&.has-sign {
		border-color: var(--el-color-primary);
	}

	.preview-image {
		width: 100%;
		height: 100%;
		object-fit: contain;
	}

	.placeholder {
		height: 100%;
		display: flex;
		align-items: center;
		justify-content: center;
		color: #909399;

		.el-icon {
			margin-right: 8px;
			font-size: 18px;
		}
	}
}
</style>

<el-form ref="dataFormRef" :model="form" inline :rules="dataRules">
    <el-form-item label="经办人签字" prop="signatureHandler" label-width="8em">
		<!-- 签名组件 -->
		<signature-component v-model="form.signatureHandler" />
    </el-form-item>
</el-form>