## 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
<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>

<script>
  export default {
    data() {
      return {
        fits: ['fill', 'contain', 'cover', 'none', 'scale-down'],
        url: 'https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg',
      }
    },
  }
</script>
<!--
<setup>

  import { defineComponent, reactive, toRefs } from 'vue';

  export default defineComponent({
    setup() {
      const state = reactive({
        fits: ['fill', 'contain', 'cover', 'none', 'scale-down'],
        url: 'https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg'
      });

      return {
        ...toRefs(state),
      };
    },
  });
</setup>
-->
```

:::

### 占位内容

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

```html
<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>

<script>
  export default {
    data() {
      return {
        src: 'https://cube.elemecdn.com/6/94/4d3ea53c084bad6931a56d5158a48jpeg.jpeg',
      }
    },
  }
</script>
<!--
<setup>

  import { defineComponent, ref } from 'vue';

  export default defineComponent({
    setup() {
      const src = ref('https://cube.elemecdn.com/6/94/4d3ea53c084bad6931a56d5158a48jpeg.jpeg');

      return {
        src,
      };
    },
  });

</setup>
-->
```

:::

### 加载失败

:::demo 可通过`slot = error`可自定义加载失败内容

```html
<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>
```

:::

### 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
<div class="demo-image__lazy">
  <el-image v-for="url in urls" :key="url" :src="url" lazy></el-image>
</div>

<script>
  export default {
    data() {
      return {
        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',
        ],
      }
    },
  }
</script>
<!--
<setup>
  import { defineComponent, ref } from 'vue';

  export default defineComponent({
    setup() {
      const urls = ref([
        '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 {
        urls,
      };
    },
  });

</setup>
-->
```

:::

### 大图预览

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

```html
<div class="demo-image__preview">
  <el-image
    style="width: 100px; height: 100px"
    :src="url"
    :preview-src-list="srcList"
  >
  </el-image>
</div>

<script>
  export default {
    data() {
      return {
        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',
        ],
      }
    },
  }
</script>
<!--
<setup>

  import { defineComponent, ref } from 'vue';

  export default defineComponent({
    setup() {
      const url = ref('https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg');
      const srcList = ref([
        'https://fuss10.elemecdn.com/8/27/f01c15bb73e1ef3793e64e6b7bbccjpeg.jpeg',
        'https://fuss10.elemecdn.com/1/8e/aeffeb4de74e2fde4bd74fc7b4486jpeg.jpeg',
      ]);

      return {
        url,
        srcList,
      };
    },
  });

</setup>
-->
```

:::

### Image Attributes

| 参数                | 说明                                                                                                     | 类型                 | 可选值                                     | 默认值                                         |
| ------------------- | -------------------------------------------------------------------------------------------------------- | -------------------- | ------------------------------------------ | ---------------------------------------------- |
| alt                 | 原生 alt                                                                                                 | 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 | -                                              |
| hide-on-click-modal | 当开启 preview 功能时，是否可以通过点击遮罩层关闭 preview                                                | boolean              | true / false                               | false                                          |
| lazy                | 是否开启懒加载                                                                                           | boolean              | —                                          | false                                          |
| preview-src-list    | 开启图片预览功能                                                                                         | Array                | —                                          | -                                              |
| referrer-policy     | 原生 referrerPolicy                                                                                      | string               | -                                          | -                                              |
| src                 | 图片源，同原生                                                                                           | string               | —                                          | -                                              |
| 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 |
| z-index             | 设置图片预览的 z-index                                                                                   | Number               | —                                          | 2000                                           |
| append-to-body      | image 自身是否插入至 body 元素上。嵌套的父元素设置了 transform 属性必须指定该属性并赋值为 true           | boolean              | —                                          | false                                          |

### Image 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) |

### Image Slots

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

### ImageViewer Attributes

| 参数                | 说明                                   | 类型            | 可选值              | 默认值 |
| ------------------- | -------------------------------------- | --------------- | ------------------- | ------ |
| url-list            | 用于预览的图片链接列表                 | Array\<string\> | -                   | []     |
| z-index             | 预览时遮罩层的 z-index                 | number / string | int / string\<int\> | 2000   |
| initial-index       | 预览的首张图片的位置, 小于等于数组长度 | number          | int                 | 0      |
| infinite            | 是否可以无限循环预览                   | boolean         | true / false        | true   |
| hide-on-click-modal | 是否可以通过点击遮罩层关闭预览         | boolean         | true / false        | false  |

### ImageViewer Events

| 事件名称 | 说明                                                               | 回调参数                     |
| -------- | ------------------------------------------------------------------ | ---------------------------- |
| close    | 当点击 X 按钮或者在 hide-on-click-modal 为 true 时点击遮罩层时触发 | 无                           |
| switch   | 当图片切换时触发                                                   | (val: number) 切换目标的下标 |