## Image 图片

图片容器，在保留原生 img 的特性下，支持懒加载，自定义占位、加载失败等

### 基础用法

:::demo 可通过`fit`确定图片如何适应到容器框，同原生 [object-fit](https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit)。

```html
<template>
  <div class="demo-image">
    <div class="block" v-for="fit in fits" :key="fit">
      <span class="demonstration">{{ fit }}</span>
      <el-image
        style="width: 100px; height: 100px"
        :src="url"
        :fit="fit"
      ></el-image>
    </div>
  </div>
</template>
<script>
  import { reactive, toRefs } from 'vue'
  export default {
    setup() {
      let state = reactive({
        fits: ['fill', 'contain', 'cover', 'none', 'scale-down'],
        url:
          'https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg'
      })
      return { ...toRefs(state) }
    }
  }
</script>
```

:::

### 占位内容

:::demo 可通过`v-slot:placeholder`可自定义占位内容

```html
<template>
  <div class="demo-image__placeholder">
    <div class="block">
      <span class="demonstration">默认</span>
      <el-image :src="src"></el-image>
    </div>
    <div class="block">
      <span class="demonstration">自定义</span>
      <el-image :src="src">
        <template #placeholder>
          <div class="image-slot">加载中<span class="dot">...</span></div>
        </template>
      </el-image>
    </div>
  </div>
</template>
<script>
  import { ref } from 'vue'
  export default {
    setup() {
      let src = ref(
        'https://cube.elemecdn.com/6/94/4d3ea53c084bad6931a56d5158a48jpeg.jpeg'
      )
      return { src }
    }
  }
</script>
```

:::

### 加载失败

:::demo 可通过`v-slot:error`可自定义加载失败内容

```html
<template>
  <div class="demo-image__error">
    <div class="block">
      <span class="demonstration">默认</span>
      <el-image></el-image>
    </div>
    <div class="block">
      <span class="demonstration">自定义</span>
      <el-image>
        <template #error>
          <div class="image-slot">
            <i class="el-icon-picture-outline"></i>
          </div>
        </template>
      </el-image>
    </div>
  </div>
</template>
```

:::

### 懒加载

:::demo 可通过`lazy`开启懒加载功能，当图片滚动到可视范围内才会加载。可通过`scroll-container`来设置滚动容器，若未定义，则为最近一个`overflow`值为`auto`或`scroll`的父元素。

```html
<template>
  <div class="demo-image__lazy">
    <el-image v-for="url in urls" :key="url" :src="url" lazy></el-image>
  </div>
</template>
<script>
  import { reactive, toRefs } from 'vue'
  export default {
    setup() {
      let state = reactive({
        urls: [
          'https://fuss10.elemecdn.com/a/3f/3302e58f9a181d2509f3dc0fa68b0jpeg.jpeg',
          'https://fuss10.elemecdn.com/1/34/19aa98b1fcb2781c4fba33d850549jpeg.jpeg',
          'https://fuss10.elemecdn.com/0/6f/e35ff375812e6b0020b6b4e8f9583jpeg.jpeg',
          'https://fuss10.elemecdn.com/9/bb/e27858e973f5d7d3904835f46abbdjpeg.jpeg',
          'https://fuss10.elemecdn.com/d/e6/c4d93a3805b3ce3f323f7974e6f78jpeg.jpeg',
          'https://fuss10.elemecdn.com/3/28/bbf893f792f03a54408b3b7a7ebf0jpeg.jpeg',
          'https://fuss10.elemecdn.com/2/11/6535bcfb26e4c79b48ddde44f4b6fjpeg.jpeg'
        ]
      })
      return { ...toRefs(state) }
    }
  }
</script>
```

:::

### 大图预览

:::demo 可通过 `previewSrcList` 开启预览大图的功能。

```html
<template>
  <div class="demo-image__preview">
    <el-image
      style="width: 100px; height: 100px"
      :src="url"
      :preview-src-list="srcList"
    >
    </el-image>
  </div>
</template>
<script>
  import { reactive, toRefs } from 'vue'
  export default {
    setup() {
      let state = reactive({
        url:
          'https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg',
        srcList: [
          'https://fuss10.elemecdn.com/8/27/f01c15bb73e1ef3793e64e6b7bbccjpeg.jpeg',
          'https://fuss10.elemecdn.com/1/8e/aeffeb4de74e2fde4bd74fc7b4486jpeg.jpeg'
        ]
      })
      return { ...toRefs(state) }
    }
  }
</script>
```

:::

### Attributes

| 参数             | 说明                                                                                                     | 类型                 | 可选值                                     | 默认值                                         |
| ---------------- | -------------------------------------------------------------------------------------------------------- | -------------------- | ------------------------------------------ | ---------------------------------------------- |
| src              | 图片源，同原生                                                                                           | string               | —                                          | -                                              |
| fit              | 确定图片如何适应容器框，同原生 [object-fit](https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit) | string               | fill / contain / cover / none / scale-down | -                                              |
| alt              | 原生 alt                                                                                                 | string               | -                                          | -                                              |
| referrer-policy  | 原生 referrerPolicy                                                                                      | string               | -                                          | -                                              |
| lazy             | 是否开启懒加载                                                                                           | boolean              | —                                          | false                                          |
| scroll-container | 开启懒加载后，监听 scroll 事件的容器                                                                     | string / HTMLElement | —                                          | 最近一个 overflow 值为 auto 或 scroll 的父元素 |
| preview-src-list | 开启图片预览功能                                                                                         | Array                | —                                          | -                                              |
| z-index          | 设置图片预览的 z-index                                                                                   | Number               | —                                          | 2000                                           |

### Events

| 事件名称 | 说明             | 回调参数   |
| -------- | ---------------- | ---------- |
| load     | 图片加载成功触发 | (e: Event) |
| error    | 图片加载失败触发 | (e: Error) |

### Slots

| 名称        | 说明                 |
| ----------- | -------------------- |
| placeholder | 图片未加载的占位内容 |
| error       | 加载失败的内容       |
