element-ui element-plus image - 分析

源代码地址 - iamge
源代码地址 - iamge-viewer

version:element-plus 1.0.1-beta.0

image

<template>
  <div
    ref="container"
    :class="['el-image', $attrs.class]"
    :style="$attrs.style"
  >
    
    <slot v-if="loading" name="placeholder">
      <div class="el-image__placeholder">div>
    slot>
    
    <slot v-else-if="hasLoadError" name="error">
      <div class="el-image__error">{
    { t('el.image.error') }}div>
    slot>
    
    <img
      v-else
      class="el-image__inner"
      v-bind="attrs"
      :src="src"
      :style="imageStyle"
      :class="{ 'el-image__inner--center': alignCenter, 'el-image__preview': preview }"
      @click="clickHandler"
    >
    <template v-if="preview">
      <image-viewer
        v-if="showViewer"
        :z-index="zIndex"
        :initial-index="imageIndex"
        :on-close="closeViewer"
        :url-list="previewSrcList"
      />
    template>
  div>
template>

<script lang='ts'>

import {
      defineComponent, computed, ref, onMounted, onBeforeUnmount, watch, nextTick } from 'vue'
import {
      isString } from '@vue/shared'
import throttle from 'lodash/throttle'
import {
      useAttrs } from '@element-plus/hooks'
import isServer from '@element-plus/utils/isServer'
import {
      on, off, getScrollContainer, isInContainer } from '@element-plus/utils/dom'
import {
      t } from '@element-plus/locale'
import ImageViewer from './image-viewer.vue'

// 是否支持 ObjectFit
const isSupportObjectFit = () => document.documentElement.style.objectFit !== undefined
// 是不是元素节点
const isHtmlEle = e => e && e.nodeType === 1

const ObjectFit = {
     
  NONE: 'none',
  CONTAIN: 'contain',
  COVER: 'cover',
  FILL: 'fill',
  SCALE_DOWN: 'scale-down',
}

let prevOverflow = '' // 存放 body 的 overflow

export default defineComponent({
     
  name: 'ElImage',
  components: {
     
    ImageViewer,
  },
  inheritAttrs: false,
  props: {
     
    src: {
     
      type: String,
      default: '',
    },
    fit: {
     
      type: String,
      default: '',
    },
    lazy: {
     
      type: Boolean,
      default: false,
    },
    scrollContainer: {
     
      type: [String, Object],
      default: null,
    },
    // 开启图片预览功能
    previewSrcList: {
     
      type: Array,
      default: () => [],
    },
    zIndex: {
     
      type: Number,
      default: 2000,
    },
  },
  emits: ['error'],
  setup(props, {
      emit }) {
     
    // init here
    // 排除 class 和 style 和 on开头的事件 所有attrs
    const attrs = useAttrs()
    const hasLoadError = ref(false)
    const loading = ref(true)
    const imgWidth = ref(0)
    const imgHeight = ref(0)
    const showViewer = ref(false)
    const container = ref<HTMLElement | null>(null)

    let _scrollContainer = null
    let _lazyLoadHandler = null

    const imageStyle = computed(() => {
     
      const {
      fit } = props
      if (!isServer && fit) {
     
        return isSupportObjectFit()
          ? {
      'object-fit': fit }
          : getImageStyle(fit)
      }
      return {
     }
    })

    const alignCenter = computed(() => {
     
      const {
      fit } = props
      return !isServer && !isSupportObjectFit() && fit !== ObjectFit.FILL
    })

    const preview = computed(() => {
     
      const {
      previewSrcList } = props
      return Array.isArray(previewSrcList) && previewSrcList.length > 0
    })
    const imageIndex = computed(() => {
     
      const {
      src , previewSrcList } = props
      let previewIndex = 0
      const srcIndex = previewSrcList.indexOf(src)
      if (srcIndex >= 0) {
     
        previewIndex = srcIndex
      }
      return previewIndex
    })


    function getImageStyle(fit) {
     
      const imageWidth = imgWidth.value
      const imageHeight = imgHeight.value

      if (!container.value) return {
     }
      const {
     
        clientWidth: containerWidth,
        clientHeight: containerHeight,
      } = container.value
      if (!imageWidth || !imageHeight || !containerWidth || !containerHeight) return {
     }

      // 是否是垂直的
      // 宽 < 高
      const vertical = imageWidth / imageHeight < 1

      // https://developer.mozilla.org/zh-CN/docs/Web/CSS/object-fit
      // scale-down:内容的尺寸与 none 或 contain 中的一个相同，取决于它们两个之间谁得到的对象尺寸会更小一些。
      if (fit === ObjectFit.SCALE_DOWN) {
     
        // 实现
        // 图片宽高都小于容器宽高就取 none 不然 contain
        const isSmaller = imageWidth < containerWidth && imageHeight < containerHeight
        fit = isSmaller ? ObjectFit.NONE : ObjectFit.CONTAIN
      }

      switch (fit) {
     
        case ObjectFit.NONE:
          return {
      width: 'auto', height: 'auto' }
        case ObjectFit.CONTAIN:
          return vertical ? {
      width: 'auto' } : {
      height: 'auto' }
        case ObjectFit.COVER:
          return vertical ? {
      height: 'auto' } : {
      width: 'auto' }
        default:
          return {
     }
      }
    }

    const loadImage = () => {
     
      if (isServer) return

      const attributes = attrs.value

      // reset status
      loading.value = true
      hasLoadError.value = false

      const img = new Image()
      img.onload = e => handleLoad(e, img)
      img.onerror = handleError

      // bind html attrs
      // so it can behave consistently
      Object.keys(attributes)
        .forEach(key => {
     
          const value = attributes[key]
          img.setAttribute(key, value)
        })
      img.src = props.src
    }

    // image load 成功函数
    function handleLoad(e: Event, img: HTMLImageElement) {
     
      imgWidth.value = img.width
      imgHeight.value = img.height
      loading.value = false
      hasLoadError.value = false
    }

    // image load 失败函数
    function handleError(e: Event) {
     
      loading.value = false
      hasLoadError.value = true
      emit('error', e)
    }

    // 懒加载处理函数
    function handleLazyLoad() {
     
      // 根据rect 判断在不在容器内
      if (isInContainer(container.value, _scrollContainer)) {
     
        loadImage()
        removeLazyLoadListener()
      }
    }

    function addLazyLoadListener() {
     
      if (isServer) return

      const {
      scrollContainer } = props
      // 如果是元素节点 直接取
      if (isHtmlEle(scrollContainer)) {
     
        _scrollContainer = scrollContainer
      }
      else if (isString(scrollContainer) && scrollContainer !== '') {
     
        // 是字符串且不为空字符串
        _scrollContainer = document.querySelector(scrollContainer)
      } else {
     
        // 基本上就是找他的父节点 最高到window
        _scrollContainer = getScrollContainer(container.value)
      }
      if (_scrollContainer) {
     
        _lazyLoadHandler = throttle(handleLazyLoad, 200)
        on(_scrollContainer, 'scroll', _lazyLoadHandler)
        setTimeout(() => handleLazyLoad(), 100)
      }
    }

    function removeLazyLoadListener() {
     
      if (isServer || !_scrollContainer || !_lazyLoadHandler) return

      off(_scrollContainer, 'scroll', _lazyLoadHandler)
      _scrollContainer = null
      _lazyLoadHandler = null
    }

    // 图片点击 预览
    function clickHandler() {
     
      // don't show viewer when preview is false
      if (!preview.value) {
     
        return
      }
      // prevent body scroll
      prevOverflow = document.body.style.overflow
      document.body.style.overflow = 'hidden'
      // 渲染 viewer
      showViewer.value = true
    }

    function closeViewer() {
     
      // 恢复 body 的 overflow
      document.body.style.overflow = prevOverflow
      showViewer.value = false
    }

    // 接收到src变更 就开始加载图片
    watch(() => props.src, () => {
     
      loadImage()
    })

    onMounted(() => {
     
      if (props.lazy) {
     
        nextTick(addLazyLoadListener)
      } else {
     
        loadImage()
      }
    })

    onBeforeUnmount(() => {
     
      props.lazy && removeLazyLoadListener()
    })

    return {
     
      attrs,
      loading,
      hasLoadError,
      showViewer,
      imgWidth,
      imgHeight,
      imageStyle,
      alignCenter,
      preview,
      imageIndex,
      clickHandler,
      closeViewer,
      container,
      handleError,
      t,
    }
  },
})
</script>

image-viewer

• 这个组件element-ui没有暴露出来，但是可以用来当预览图使用

<template>
  <transition name="viewer-fade">
    <div
      ref="wrapper"
      tabindex="-1"
      class="el-image-viewer__wrapper"
      :style="{
         'z-index': zIndex }"
    >
      <div class="el-image-viewer__mask">div>
      
      <span class="el-image-viewer__btn el-image-viewer__close" @click="hide">
        <i class="el-icon-circle-close">i>
      span>
      
      
      <template v-if="!isSingle">
        
        
        <span
          class="el-image-viewer__btn el-image-viewer__prev"
          :class="{ 'is-disabled': !infinite && isFirst }"
          @click="prev"
        >
          <i class="el-icon-arrow-left">i>
        span>
        
        <span
          class="el-image-viewer__btn el-image-viewer__next"
          :class="{ 'is-disabled': !infinite && isLast }"
          @click="next"
        >
          <i class="el-icon-arrow-right">i>
        span>
      template>
      
      
      <div class="el-image-viewer__btn el-image-viewer__actions">
        <div class="el-image-viewer__actions__inner">
          <i class="el-icon-zoom-out" @click="handleActions('zoomOut')">i>
          <i class="el-icon-zoom-in" @click="handleActions('zoomIn')">i>
          <i class="el-image-viewer__actions__divider">i>
          <i :class="mode.icon" @click="toggleMode">i>
          <i class="el-image-viewer__actions__divider">i>
          <i class="el-icon-refresh-left" @click="handleActions('anticlocelise')">i>
          <i class="el-icon-refresh-right" @click="handleActions('clocelise')">i>
        div>
      div>
      
      <div class="el-image-viewer__canvas">
        <img
          v-for="(url, i) in urlList"
          v-show="i === index"
          ref="img"
          :key="url"
          :src="currentImg"
          :style="imgStyle"
          class="el-image-viewer__img"
          @load="handleImgLoad"
          @error="handleImgError"
          @mousedown="handleMouseDown"
        >
      div>
    div>
  transition>
template>

<script lang='ts'>

import {
      defineComponent, computed, ref, onMounted, watch, nextTick, PropType } from 'vue'
import {
      rafThrottle, isFirefox } from '@element-plus/utils/util'
import {
      on, off } from '@element-plus/utils/dom'
import {
      EVENT_CODE } from '@element-plus/utils/aria'
import {
      t } from '@element-plus/locale'

const Mode = {
     
  CONTAIN: {
     
    name: 'contain',
    icon: 'el-icon-full-screen',
  },
  ORIGINAL: {
     
    name: 'original',
    icon: 'el-icon-c-scale-to-original',
  },
}

const mousewheelEventName = isFirefox() ? 'DOMMouseScroll' : 'mousewheel'

export default defineComponent({
     
  name: 'ElImageViewer',
  props: {
     
    urlList: {
     
      type: Array as PropType<string[]>,
      default: () => [],
    },
    zIndex: {
     
      type: Number,
      default: 2000,
    },
    onSwitch: {
     
      type: Function,
      default: () => ({
     }),
    },
    onClose: {
     
      type: Function,
      default: () => ({
     }),
    },
    initialIndex: {
     
      type: Number,
      default: 0,
    },
  },

  setup(props) {
     
    // init here

    let _keyDownHandler = null
    let _mouseWheelHandler = null
    let _dragHandler = null

    const loading = ref(true)
    const index = ref(props.initialIndex)
    const infinite = ref(true)
    const wrapper = ref(null)
    const img = ref(null)
    const mode = ref(Mode.CONTAIN)
    let transform = ref({
     
      scale: 1,
      deg: 0,
      offsetX: 0,
      offsetY: 0,
      enableTransition: false,
    })

    const isSingle = computed(() => {
     
      const {
      urlList } = props
      return urlList.length <= 1
    })

    const isFirst = computed(() => {
     
      return index.value === 0
    })

    const isLast = computed(() => {
     
      return index.value === 0
    })

    // 渠道当前 active image 的 src
    const currentImg = computed(() => {
     
      return props.urlList[index.value]
    })

    const imgStyle = computed(() => {
     
      const {
      scale, deg, offsetX, offsetY, enableTransition } = transform.value
      const style = {
     
        transform: `scale(${
       scale}) rotate(${
       deg}deg)`,
        transition: enableTransition ? 'transform .3s' : '',
        'margin-left': `${
       offsetX}px`,
        'margin-top': `${
       offsetY}px`,
      }
      if (mode.value.name === Mode.CONTAIN.name) {
     
        style.maxWidth = style.maxHeight = '100%'
      }
      return style
    })

    function hide() {
     
      deviceSupportUninstall()
      props.onClose()
    }

    function deviceSupportInstall() {
     
      // 键盘事件
      _keyDownHandler = rafThrottle(e => {
     
        switch (e.code) {
     
          // ESC
          case EVENT_CODE.esc:
            hide()
            break
          // SPACE
          case EVENT_CODE.space:
            toggleMode()
            break
          // LEFT_ARROW
          case EVENT_CODE.left:
            prev()
            break
          // UP_ARROW
          case EVENT_CODE.up:
            handleActions('zoomIn')
            break
          // RIGHT_ARROW
          case EVENT_CODE.right:
            next()
            break
          // DOWN_ARROW
          case EVENT_CODE.down:
            handleActions('zoomOut')
            break
        }
      })

      // 鼠标事件
      _mouseWheelHandler = rafThrottle(e => {
     
        const delta = e.wheelDelta ? e.wheelDelta : -e.detail
        if (delta > 0) {
     
          handleActions('zoomIn', {
     
            zoomRate: 0.015,
            enableTransition: false,
          })
        } else {
     
          handleActions('zoomOut', {
     
            zoomRate: 0.015,
            enableTransition: false,
          })
        }
      })
      on(document, 'keydown', _keyDownHandler)
      on(document, mousewheelEventName, _mouseWheelHandler)
    }

    function deviceSupportUninstall() {
     
      off(document, 'keydown', _keyDownHandler)
      off(document, mousewheelEventName, _mouseWheelHandler)
      _keyDownHandler = null
      _mouseWheelHandler = null
    }

    function handleImgLoad() {
     
      loading.value = false
    }

    function handleImgError(e) {
     
      loading.value = false
      e.target.alt = t('el.image.error')
    }

    function handleMouseDown(e) {
     
      if (loading.value || e.button !== 0) return

      const {
      offsetX, offsetY } = transform.value
      const startX = e.pageX
      const startY = e.pageY
      // requestAnimationFrame throttle
      _dragHandler = rafThrottle(ev => {
     
        transform.value = {
     
          ...transform.value,
          offsetX: offsetX + ev.pageX - startX,
          offsetY: offsetY + ev.pageY - startY,
        }
      })
      on(document, 'mousemove', _dragHandler)
      on(document, 'mouseup', () => {
     
        off(document, 'mousemove', _dragHandler)
      })

      e.preventDefault()
    }

    function reset() {
     
      transform.value = {
     
        scale: 1,
        deg: 0,
        offsetX: 0,
        offsetY: 0,
        enableTransition: false,
      }
    }

    function toggleMode() {
     
      if (loading.value) return

      const modeNames = Object.keys(Mode)
      const modeValues = Object.values(Mode)
      const currentMode = mode.value.name
      const index = modeValues.findIndex(i => i.name === currentMode)
      // ! 厉害
      const nextIndex = (index + 1) % modeNames.length
      mode.value = Mode[modeNames[nextIndex]]
      reset()
    }

    function prev() {
     
      if (isFirst.value && !infinite.value) return
      const len = props.urlList.length
      // + len 防止 < len
      index.value = (index.value - 1 + len) % len
    }

    function next() {
     
      if (isLast.value && !infinite.value) return
      const len = props.urlList.length
      index.value = (index.value + 1) % len
    }

    function handleActions(action, options = {
     }) {
     
      if (loading.value) return
      const {
      zoomRate, rotateDeg, enableTransition } = {
     
        zoomRate: 0.2,
        rotateDeg: 90,
        enableTransition: true,
        ...options,
      }
      switch (action) {
     
        case 'zoomOut':
          // 最小缩放 0.2
          if (transform.value.scale > 0.2) {
     
            // 保留三位 浏览器 四舍五入 保留两位
            transform.value.scale = parseFloat((transform.value.scale - zoomRate).toFixed(3))
          }
          break
        case 'zoomIn':
          // 最大缩放没有限制
          transform.value.scale = parseFloat((transform.value.scale + zoomRate).toFixed(3))
          break
        case 'clocelise':
          transform.value.deg += rotateDeg
          break
        case 'anticlocelise':
          transform.value.deg -= rotateDeg
          break
      }
      transform.value.enableTransition = enableTransition
    }

    // 监听当前图片
    watch(currentImg, () => {
     
      nextTick(() => {
     
        const $img = img.value
        if (!$img.complete) {
     
          loading.value = true
        }
      })
    })

    // index 更新 reset
    watch(index, val => {
     
      reset()
      props.onSwitch(val)
    })

    onMounted(() => {
     
      deviceSupportInstall()
      // add tabindex then wrapper can be focusable via Javascript
      // focus wrapper so arrow key can't cause inner scroll behavior underneath
      wrapper.value?.focus()
    })

    return {
     
      index,
      wrapper,
      img,
      infinite: true, // ? 为啥写死
      loading: false, // template 没有用到
      isSingle,
      isFirst,
      isLast,
      currentImg,
      imgStyle,
      mode,
      handleActions,
      prev,
      next,
      hide,
      toggleMode,
      handleImgLoad,
      handleImgError,
      handleMouseDown,
    }
  },
})
</script>