canvas 图片水印

复制代码
<template>
  <div class="image-watermark-container">
    <!-- 页面标题 -->
    <h1 class="page-title">图片水印工具</h1>
    
    <!-- 主内容区 -->
    <el-row :gutter="20" class="main-content">
      <!-- 左侧控制面板 -->
      <el-col :span="8" class="control-panel">
        <el-card class="control-card">
          <template #header>
            <div class="card-header">
              <i class="el-icon-setting"></i>
              <span>水印设置</span>
            </div>
          </template>
          
          <!-- 图片上传区域 -->
          <el-upload
            class="image-uploader"
            action=""
            :show-file-list="false"
            :before-upload="handleBeforeUpload"
            :http-request="handleFileUpload"
          >
            <div class="upload-area" :class="{ 'has-image': originalImage }">
              <i v-if="!originalImage" class="el-icon-upload"></i>
              <img v-if="originalImage" :src="originalImage" class="preview-image" alt="预览图">
              <div v-if="!originalImage" class="upload-text">
                <p>点击或拖拽图片到此处上传</p>
                <p class="upload-hint">支持 JPG, PNG, GIF 等格式</p>
              </div>
              <el-button 
                v-if="originalImage" 
                type="text" 
                class="remove-image" 
                @click.stop="removeImage"
              >
                <i class="el-icon-delete"></i> 移除图片
              </el-button>
            </div>
          </el-upload>
          
          <el-divider v-if="originalImage"></el-divider>
          
          <!-- 水印设置项 -->
          <div v-if="originalImage" class="watermark-settings">
            <el-form label-position="top" size="medium">
              <el-form-item label="水印文本">
                <el-input 
                  v-model="watermarkText" 
                  placeholder="请输入水印文字"
                  clearable
                ></el-input>
              </el-form-item>
              
              <el-row :gutter="15">
                <el-col :span="12">
                  <el-form-item label="字体大小 (px)">
                    <el-input-number 
                      v-model="fontSize" 
                      :min="10" 
                      :max="100" 
                      :step="1"
                    ></el-input-number>
                  </el-form-item>
                </el-col>
                <el-col :span="12">
                  <el-form-item label="水印颜色">
                    <el-color-picker 
                      v-model="watermarkColor" 
                      :predefine="predefinedColors"
                      show-alpha
                    ></el-color-picker>
                  </el-form-item>
                </el-col>
              </el-row>
              
              <el-form-item label="透明度">
                <el-slider 
                  v-model="opacity" 
                  :min="0" 
                  :max="1" 
                  :step="0.1"
                  show-stops
                ></el-slider>
                <div class="slider-value">{{ opacity.toFixed(1) }}</div>
              </el-form-item>
              
              <el-row :gutter="15">
                <el-col :span="12">
                  <el-form-item label="旋转角度 (度)">
                    <el-input-number 
                      v-model="rotation" 
                      :min="-180" 
                      :max="180" 
                      :step="1"
                    ></el-input-number>
                  </el-form-item>
                </el-col>
                <el-col :span="12">
                  <el-form-item label="水印间距 (px)">
                    <el-input-number 
                      v-model="spacing" 
                      :min="10" 
                      :max="100" 
                      :step="1"
                    ></el-input-number>
                  </el-form-item>
                </el-col>
              </el-row>
              
              <el-form-item>
                <el-button 
                  type="primary" 
                  class="generate-btn" 
                  @click="addWatermark"
                  :loading="isProcessing"
                >
                  <i class="el-icon-magic"></i> 生成水印图片
                </el-button>
              </el-form-item>
            </el-form>
          </div>
        </el-card>
      </el-col>
      
      <!-- 右侧预览区域 -->
      <el-col :span="16" class="preview-panel">
        <el-card class="preview-card">
          <template #header>
            <div class="card-header">
              <i class="el-icon-picture"></i>
              <span>图片预览</span>
            </div>
          </template>
          
          <div class="preview-container">
            <!-- 原图预览 -->
            <div class="preview-section">
              <h3 class="preview-title">
                <i class="el-icon-picture-outline"></i> 原图
              </h3>
              <div class="image-container">
                <img 
                  v-if="originalImage" 
                  :src="originalImage" 
                  class="preview-img" 
                  alt="原始图片"
                >
                <div v-else class="empty-state">
                  <i class="el-icon-picture-outline"></i>
                  <p>请上传图片查看预览</p>
                </div>
              </div>
            </div>
            
            <!-- 水印图预览 -->
            <div class="preview-section">
              <h3 class="preview-title">
                <i class="el-icon-picture"></i> 带水印图片
              </h3>
              <div class="image-container">
                <img 
                  v-if="watermarkedImage" 
                  :src="watermarkedImage" 
                  class="preview-img" 
                  alt="带水印的图片"
                >
                <div v-else class="empty-state">
                  <i class="el-icon-hourglass"></i>
                  <p>请点击生成水印图片</p>
                </div>
              </div>
              
              <el-button 
                v-if="watermarkedImage"
                type="success" 
                class="download-btn" 
                @click="downloadImage"
                icon="el-icon-download"
              >
                下载图片
              </el-button>
            </div>
          </div>
        </el-card>
      </el-col>
    </el-row>
  </div>
</template>

<script>
export default {
  data() {
    return {
      // 图片相关
      originalImage: null,
      watermarkedImage: null,
      isProcessing: false,
      
      // 水印设置
      watermarkText: '水印文字',
      fontSize: 24,
      watermarkColor: 'rgba(0, 0, 0, 0.3)',
      opacity: 0.3,
      rotation: -30,
      spacing: 50,
      
      // 预定义颜色
      predefinedColors: [
        'rgba(0, 0, 0, 0.3)',
        'rgba(255, 0, 0, 0.3)',
        'rgba(0, 255, 0, 0.3)',
        'rgba(0, 0, 255, 0.3)',
        'rgba(255, 255, 255, 0.3)',
      ]
    };
  },
  methods: {
    // 处理上传前的验证
    handleBeforeUpload(file) {
      const isImage = file.type.startsWith('image/');
      if (!isImage) {
        this.$message.error('请上传图片文件！');
        return false;
      }
      return true;
    },
    
    // 处理文件上传
    handleFileUpload(params) {
      const file = params.file;
      const reader = new FileReader();
      
      reader.onload = (event) => {
        this.originalImage = event.target.result;
        this.watermarkedImage = null; // 重置水印图片
        this.$message.success('图片上传成功');
      };
      
      reader.readAsDataURL(file);
    },
    
    // 移除图片
    removeImage() {
      this.originalImage = null;
      this.watermarkedImage = null;
    },
    
    // 添加水印
    addWatermark() {
      if (!this.originalImage) return;
      
      this.isProcessing = true;
      
      // 使用setTimeout模拟异步处理，提升用户体验
      setTimeout(() => {
        const img = new Image();
        img.src = this.originalImage;
        
        img.onload = () => {
          // 创建Canvas
          const canvas = document.createElement('canvas');
          const ctx = canvas.getContext('2d');
          
          // 设置Canvas尺寸与图片一致
          canvas.width = img.width;
          canvas.height = img.height;
          
          // 绘制原图
          ctx.drawImage(img, 0, 0);
          
          // 设置水印样式
          ctx.fillStyle = this.watermarkColor;
          ctx.globalAlpha = this.opacity;
          ctx.font = `${this.fontSize}px Arial`;
          ctx.textAlign = 'center';
          ctx.textBaseline = 'middle';
          
          // 计算水印旋转角度（弧度）
          const angle = (this.rotation * Math.PI) / 180;
          
          // 获取水印文本宽度
          const textWidth = ctx.measureText(this.watermarkText).width;
          
          // 计算水印网格大小
          const gridWidth = textWidth + this.spacing;
          const gridHeight = this.fontSize + this.spacing;
          
          // 计算需要覆盖的水印数量（考虑旋转后的覆盖范围）
          const diagonal = Math.sqrt(canvas.width * canvas.width + canvas.height * canvas.height);
          const cols = Math.ceil(diagonal / gridWidth) + 1;
          const rows = Math.ceil(diagonal / gridHeight) + 1;
          
          // 绘制水印网格
          for (let i = -cols/2; i < cols/2; i++) {
            for (let j = -rows/2; j < rows/2; j++) {
              // 计算水印位置
              const x = canvas.width / 2 + i * gridWidth;
              const y = canvas.height / 2 + j * gridHeight;
              
              // 保存当前状态
              ctx.save();
              
              // 移动到水印位置并旋转
              ctx.translate(x, y);
              ctx.rotate(angle);
              
              // 绘制水印文本
              ctx.fillText(this.watermarkText, 0, 0);
              
              // 恢复状态
              ctx.restore();
            }
          }
          
          // 将Canvas内容转为图片URL
          this.watermarkedImage = canvas.toDataURL('image/png');
          this.isProcessing = false;
          this.$message.success('水印生成成功');
        };
        
        img.onerror = () => {
          this.isProcessing = false;
          this.$message.error('图片处理失败，请重试');
        };
      }, 500);
    },
    
    // 下载带水印的图片
    downloadImage() {
      if (!this.watermarkedImage) return;
      
      const link = document.createElement('a');
      link.href = this.watermarkedImage;
      link.download = 'watermarked-image.png';
      document.body.appendChild(link);
      link.click();
      document.body.removeChild(link);
      this.$message.success('图片下载成功');
    }
  }
};
</script>

<style lang="scss" scoped>
.image-watermark-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 20px;
  background-color: #f5f7fa;
  min-height: 100vh;
}

.page-title {
  color: #1f2329;
  font-size: 28px;
  font-weight: 600;
  text-align: center;
  margin-bottom: 30px;
  padding: 15px 0;
  border-bottom: 1px solid #e5e6eb;
  
  &:before, &:after {
    content: "";
    display: inline-block;
    width: 40px;
    height: 2px;
    background-color: #409eff;
    vertical-align: middle;
    margin: 0 15px;
  }
}

.main-content {
  margin-bottom: 30px;
}

.control-panel, .preview-panel {
  transition: all 0.3s ease;
}

.control-card, .preview-card {
  border-radius: 8px;
  box-shadow: 0 2px 12px 0 rgba(0, 0, 0, 0.05);
  overflow: hidden;
  transition: box-shadow 0.3s ease;
  
  &:hover {
    box-shadow: 0 4px 18px 0 rgba(0, 0, 0, 0.1);
  }
}

.card-header {
  display: flex;
  align-items: center;
  color: #1f2329;
  font-size: 16px;
  font-weight: 500;
  
  i {
    margin-right: 8px;
    color: #409eff;
  }
}

.image-uploader {
  margin-bottom: 20px;
}

.upload-area {
  border: 2px dashed #c0ccda;
  border-radius: 6px;
  padding: 30px;
  text-align: center;
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
  
  &:hover {
    border-color: #409eff;
    background-color: #f0f7ff;
  }
  
  i {
    font-size: 48px;
    color: #8392a5;
    margin-bottom: 15px;
    transition: color 0.3s ease;
  }
  
  &:hover i {
    color: #409eff;
  }
}

.upload-text {
  color: #8392a5;
  
  p {
    margin: 0;
    line-height: 1.5;
  }
  
  .upload-hint {
    font-size: 12px;
    color: #c0ccda;
  }
}

.has-image {
  border-style: solid;
  padding: 0;
  
  i, .upload-text {
    display: none;
  }
}

.preview-image {
  width: 100%;
  height: auto;
  border-radius: 4px;
  display: block;
}

.remove-image {
  position: absolute;
  top: 10px;
  right: 10px;
  background-color: rgba(0, 0, 0, 0.5);
  color: white !important;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  padding: 0 !important;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: all 0.3s ease;
  
  &:hover {
    background-color: rgba(235, 87, 87, 0.8);
  }
}

.upload-area:hover .remove-image {
  opacity: 1;
}

.watermark-settings {
  padding-top: 10px;
}

.el-form-item {
  margin-bottom: 18px;
}

.el-form-item__label {
  color: #4e5969;
  font-weight: 500;
  padding-bottom: 6px;
}

.slider-value {
  text-align: right;
  color: #8392a5;
  font-size: 12px;
  margin-top: -10px;
}

.generate-btn {
  width: 100%;
  padding: 12px 0;
  font-size: 15px;
}

.preview-container {
  padding: 10px 0;
}

.preview-section {
  margin-bottom: 30px;
  
  &:last-child {
    margin-bottom: 0;
  }
}

.preview-title {
  color: #4e5969;
  font-size: 16px;
  font-weight: 500;
  margin-bottom: 15px;
  padding-bottom: 8px;
  border-bottom: 1px solid #e5e6eb;
  
  i {
    margin-right: 8px;
    color: #409eff;
  }
}

.image-container {
  width: 100%;
  min-height: 300px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid #e5e6eb;
  border-radius: 6px;
  background-color: #fafafa;
  overflow: hidden;
}

.preview-img {
  max-width: 100%;
  max-height: 500px;
  transition: all 0.3s ease;
  
  &:hover {
    transform: scale(1.02);
  }
}

.empty-state {
  text-align: center;
  color: #8392a5;
  
  i {
    font-size: 48px;
    margin-bottom: 15px;
    opacity: 0.5;
  }
  
  p {
    margin: 0;
  }
}

.download-btn {
  display: block;
  margin: 20px auto 0;
  padding: 10px 30px;
  font-size: 14px;
  transition: all 0.3s ease;
  
  &:hover {
    transform: translateY(-2px);
  }
}

// 响应式调整
@media (max-width: 992px) {
  .control-panel, .preview-panel {
    width: 100%;
    margin-bottom: 20px;
  }
  
  .el-col {
    &:span-8, &:span-16 {
      width: 100%;
    }
  }
}

@media (max-width: 768px) {
  .image-watermark-container {
    padding: 10px;
  }
  
  .upload-area {
    padding: 20px 10px;
  }
  
  .page-title {
    font-size: 22px;
    
    &:before, &:after {
      width: 20px;
    }
  }
}
</style>