Vue自定义指令结合阿里云OSS优化图片的实现方法

图片往往在加载前端项目中占大头，如何既不损失图片质量，又提升加载速度呢？

根据显示设备pixelRatio和元素宽高来显示合适图片

略微压缩图片质量

使用webp

注册全局自定义指令

Vue.directive('img-condense', { bind: (el, binding, vnode) => { let src = el.getAttribute('src') let newSrc = compressImg(src, el) el.setAttribute('src', newSrc) } })

获取元素宽高和显示设备pixelRatio

let compressImg = (imgUrl, el) => { // 获取显示设备 pixelRatio let pixelRatio = window.devicePixelRatio let elWidth = elStyle.width * pixelRatio let elHeight = elStyle.height * pixelRatio let resize = '/resize' if (elWidth) { resize += `,w_${elWidth}` } if (elHeight) { resize += `,h_${elHeight}` } })

判断webp

let canUseWebp = document.createElement('canvas').toDataURL('image/webp').indexOf('data:image/webp') == 0 let webp = '' if (canUseWebp) { webp = '/format,webp' }

质量降低至80%

let ossParam?x-oss-process=image${resize}/auto-orient,1/quality,Q_80/bright,-1${webp}

完整版

<img v-img-condense alt="Vue logo" src="https://www.jb51.net/assets/logo.png"> Vue.directive('img-condense', { bind: (el, binding, vnode) => { let src = el.getAttribute('src') let newSrc = compressImg(src, el) el.setAttribute('src', newSrc) } }) let compressImg = (imgUrl, el) => { // 如果不是oss 或者已经压缩过的图片直接返回 if (imgUrl.includes('aliyuncs.com') || imgUrl.indexOf('blob') === 0 || imgUrl.includes('x-oss-process=')){ return imgUrl } // 获取显示设备 pixelRatio let pixelRatio = window.devicePixelRatio let elWidth = el.width * pixelRatio let elHeight = el.height * pixelRatio let resize = '/resize' if (elWidth) { resize += `,w_${elWidth}` } if (elHeight) { resize += `,h_${elHeight}` } if (!elWidth && !elHeight) { resize = '' } // 判断webp let canUseWebp = document.createElement('canvas').toDataURL('image/webp').indexOf('data:image/webp') == 0 let webp = '' if (canUseWebp) { webp = '/format,webp' } return `${imgUrl}?x-oss-process=image${resize}/auto-orient,1/quality,Q_80/bright,-1${webp}` }