前端实现图片或视频预览的三种方法总结

<input type="file" id="videoInput">
<video src="" alt="预览" id="video" controls="controls">
<script>
  const videoInput = document.getElementById('videoInput');
  videoInput.addEventListener('change', e => {
    previewByReader(e.target.files[0])
  })

function fileToBase64(file: File): Promise<{ url: any, filename: string }> {
  const fileReader = new FileReader()
  fileReader.readAsDataURL(file)
  var filename = file.name;
  return new Promise((resolve, reject) => {
    fileReader.addEventListener("loadend", (e: ProgressEvent<FileReader>) => {
      var url: any = e.target!.result;
      resolve({ url, filename })
    }, false);
  })
}
  async function previewByReader (file) {
   const {url} = await fileToBase64(file)
   video.src = url
  }
</script>

<input type="file" id="videoInput">
  <video src="" alt="预览" id="video" controls="controls" width="400" height="200">
  <script>
    const videoInput = document.getElementById('videoInput');
    videoInput.addEventListener('change', e => {
      previewByURL(e.target.files[0])
    })
    function previewByURL (file) {
      video.src = URL.createObjectURL(file)
    }
  </script>

<template>
    <div ref="previewWrapper" class="image-preview">
      <div class="overlay" v-if="showOverlay" @click="closePreview"></div>
      <div class="preview-container" v-wheelScale>
        <img :src="currentImageUrl" alt="Preview Image" @load="imageLoaded" ref="previewImage">
      </div>
      <div class="arrow arrow-left" @click="prevImage" :disabled="currentIndex === 0">&lt;</div>
      <div class="arrow arrow-right" @click="nextImage" :disabled="currentIndex === images.length - 1">&gt;</div>
    </div>
  </template>
  
  <script>
  export default {
    props: {
      images: {
        type: Array,
        required: true,
      },
    },
    data() {
      return {
        showOverlay: false,
        currentIndex: 0,
        currentImageUrl: '',
        scale: 1,
        initialMouseX: 0,
        initialScale: 1,
        isDragging: false,
      };
    },
    methods: {
      openPreview() {
        this.showOverlay = true;
        this.currentImageUrl = this.images[this.currentIndex];
        this.$refs.previewWrapper.style.display = 'flex';
        setTimeout(() => {
          this.$refs.previewWrapper.style.opacity = 1;
        }, 10);
      },
      closePreview() {
        this.showOverlay = false;
        setTimeout(() => {
          this.$refs.previewWrapper.style.opacity = 0;
          setTimeout(() => {
            this.$refs.previewWrapper.style.display = 'none';
          }, 0);
        }, 0);
      },
      nextImage() {
        this.currentIndex = (this.currentIndex + 1) % this.images.length;
        this.currentImageUrl = this.images[this.currentIndex];
      },
      prevImage() {
        this.currentIndex = (this.currentIndex - 1 + this.images.length) % this.images.length;
        this.currentImageUrl = this.images[this.currentIndex];
      },
      imageLoaded() {
        // 可以在此处调整图片的居中或其它布局逻辑
      },
    },
    mounted() {
      // 初始化时隐藏预览层
      this.$refs.previewWrapper.style.display = 'none';
    },
  };
  </script>
  
  <style scoped>
  .image-preview {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 999;
    display: none;
    justify-content: center;
    align-items: center;
    opacity: 0;
    transition: opacity 0.7s ease-in-out;
  }
  
  .overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.8);
    cursor: pointer;
  }
  
  .preview-container {
    position: relative;
    text-align: center;
    overflow: hidden;
    max-width: 90%;
    max-height: 90vh;
  }
  
  .arrow {
    width: 50px;
    height: 50px;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(255, 255, 255, 0.8);
    padding: 10px;
    border-radius: 50%;
    cursor: pointer;
    z-index: 1;
    opacity: 0.5;
    transition: opacity 0.3s;
    border: none;
    font-size: 20px;
    line-height: 50px;
  }
  
  .arrow:hover {
    opacity: 1;
  }
  
  .arrow-left {
    left: 10px;
  }
  
  .arrow-right {
    right: 10px;
  }
  </style>

export const initVWheelScale = (Vue) => {
    Vue.directive("wheelScale", (el, binding) => {
      const {
        maxScale = 5,
        minScale = 0.5,
        initScale = 1,
        cssVarName = "--scale",
      } = binding.arg || {}
      let currentScale = initScale || el.style.getPropertyValue(cssVarName) || 1
      setWheelScale(binding, {
        el,
        cssVarName,
        currentScale,
        minScale,
        maxScale,
      })
      if (el) {
        el.onwheel = (e) => {
          currentScale = el.style.getPropertyValue(cssVarName) || 1
   
          if (e.wheelDelta > 0) {
            currentScale = currentScale * 1 + 0.1
          } else {
            currentScale = currentScale * 1 - 0.1
          }
          setWheelScale(binding, {
            el,
            cssVarName,
            currentScale,
            minScale,
            maxScale,
          })
        }
      }
    })
  }
  // 设置 --scale 变量 缩放比例
  const setVarScale = (el, cssVarName, currentScale, minScale, maxScale) => {
    // 现在缩放范围
    if (currentScale > maxScale) {
      currentScale = maxScale
    } else if (currentScale < minScale) {
      currentScale = minScale
    }
    let cssText = el.style.cssText
    let cssTextList = cssText.split(";")
    let isExist = false
    let isExistIndex = -1
    for (let index = 0; index < cssTextList.length; index++) {
      const element = cssTextList[index]
      if (element.includes(cssVarName + ":")) {
        isExist = true
        isExistIndex = index
        break
      }
    }
    if (isExist) {
      cssTextList[isExistIndex] = `--scale: ${currentScale}`
    } else {
      cssTextList.push(`--scale: ${currentScale}`)
      //   el.setAttribute("style", `--scale: ${currentScale}`)
    }
    cssText = cssTextList.join(";")
    el.style.cssText = cssText
    return currentScale
  }
  // 设置 style.transform
  const setTransformCss = (el, cssVarName) => {
    let transformCssString = el.style.transform
    let regScaleGlobal = /scale\(.*?[ )]*[)]+[ ]*/g //匹配 Scale属性 全局
    if (regScaleGlobal.test(transformCssString)) {
      transformCssString = transformCssString.replace(
        regScaleGlobal,
        ` scale(var(${cssVarName})) `
      )
    } else {
      transformCssString += " " + `scale(var(${cssVarName}))`
    }
    el.style.transform = transformCssString
  }
  export const setWheelScale = (binding = {}, options) => {
    const { el, cssVarName, currentScale, minScale, maxScale } = options
    const nowScale = setVarScale(el, cssVarName, currentScale, minScale, maxScale)
    setTransformCss(el, cssVarName)
    // 缩放改变回调函数
    const wheelScaleHandle = binding.value || null
    if (wheelScaleHandle instanceof Function) {
      wheelScaleHandle({
        el,
        cssVarName,
        maxScale,
        minScale,
        currentScale: nowScale,
        setScale: (_scale) => {
          setWheelScale(binding, { ...options, currentScale: _scale })
        },
        binding,
      })
    }
  }
   

import { initVWheelScale} from "@/utils/scale.js"
initVWheelScale(Vue)

<template>
  <div>
    <!-- ...其他内容 -->
    <button @click="openPreview">预览图片</button>
    <image-preview :images="imageList" ref="imagePreview"></image-preview>
  </div>
</template>

<script>
import ImagePreview from '@/components/ImagePreview.vue'; // 引入你的图片预览组件

export default {
  components: {
    ImagePreview,
  },
  data() {
    return {
      imageList: [
        'https://img1.baidu.com/it/u=582697934,2565184993&fm=253&fmt=auto&app=120&f=JPEG?w=500&h=539',
        'https://img2.baidu.com/it/u=3519181745,2349627299&fm=253&fmt=auto&app=120&f=JPEG?w=750&h=500',
        // 更多图片路径
      ],
    };
  },
  methods: {
    openPreview() {
      this.$refs.imagePreview.openPreview();
    },
  },
};
</script>