41 lines
1.5 KiB
JavaScript
41 lines
1.5 KiB
JavaScript
/* 全站背景图定时轮换（每 6 秒切换一张，交叉淡入淡出） */
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(function () {
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var bgList = [
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'https://image.987119.xyz/uploads/2026/07/18c0005c5dac2c14635.webp',
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'https://image.987119.xyz/uploads/2026/07/18c099240bbbdcbb113.webp',
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'https://image.987119.xyz/uploads/2026/07/18c0993b4e03a5c5599.webp'
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]
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var webBg = document.getElementById('web_bg')
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if (!webBg || bgList.length < 2) return
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// 覆盖层：用于交叉淡入，避免背景瞬间硬切
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var overlay = document.createElement('div')
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overlay.id = 'web_bg_overlay'
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overlay.style.cssText =
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'position:fixed;top:0;left:0;width:100%;height:100%;z-index:-1;' +
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'background-size:cover;background-position:center;opacity:0;' +
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'transition:opacity 1.5s ease;'
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document.body.appendChild(overlay)
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var idx = 0
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var DURATION = 1500 // 淡入淡出时长(ms)，须与 CSS transition 一致
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function swap() {
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idx = (idx + 1) % bgList.length
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var url = 'url("' + bgList[idx] + '")'
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// 新图先放到覆盖层并淡入，盖住旧图
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overlay.style.backgroundImage = url
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void overlay.offsetWidth // 强制 reflow，确保过渡生效
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overlay.style.opacity = '1'
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// 过渡结束后，把底层也换成新图，再将覆盖层淡出，实现无缝循环
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setTimeout(function () {
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webBg.style.backgroundImage = url
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webBg.style.backgroundSize = 'cover'
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webBg.style.backgroundPosition = 'center'
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overlay.style.opacity = '0'
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}, DURATION)
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}
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setInterval(swap, 6000)
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})()
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