离线 · 无上传 · 浏览器本地完成Offline · no uploads · runs in the browser
WebP 转 JPEG——给不收 WebP 的接收方兜底，透明铺白WebP to JPEG for recipients that will not take WebP
这条路存在的理由通常不是压缩，而是「对方打不开」：一些邮件客户端、老版本 Office、以及某些 CMS 的上传校验都不接受 WebP。做法是把 WebP 解码到画布、铺白、再交给 JPEG 编码器，于是有两件事一定发生——透明变成白底，以及一次全新的有损编码。原始文件还在的话，交付 JPEG 从原始 PNG 走会更干净；这条适合的是「手里只有 WebP」的情形。The reason this route exists is usually not compression but “the other side cannot open it”: some mail clients, older Office builds and certain CMS upload validators will not take WebP. The mechanics are decode onto a canvas, fill white, hand it to the JPEG encoder — which means two things certainly happen: transparency becomes white, and a fresh lossy encode is performed. If the original is still around, shipping JPEG from the PNG is cleaner; this route is for the case where WebP is all you have.
这条链路怎么走How the route runs
WebPWebP JPEGJPEG
共 1 步，由扩展的路径搜索自动选出，中间产物不落盘。1 step, chosen by the extension's own path search; intermediate results never touch the disk.
会保留什么What carries over
- 透明铺纯白底，不会带出黑底或半透明残留Transparency flattens onto pure white — never a black background, never a translucent fringe
- 像素尺寸原样保留，除非你设了最长边（800–4096 px）Pixel dimensions are kept unless you set a longest edge (800–4096 px)
- 质量档 40%–90% 与目标体积 20 KB–2 MB 照旧，只在链路末尾那次编码生效Quality steps of 40%–90% and target sizes of 20 KB–2 MB apply as usual, at the route’s final encode only
- 静态 WebP 正常处理；动图 WebP 得到浏览器解码出的那一帧A still WebP is handled normally; an animated one yields the frame the browser decoded
- 一批最多 200 张、单个 100 MB 上限，结果可一次打包成 ZIPUp to 200 images per batch and 100 MB each, downloadable as one ZIP
如实说明的限制What it does not do
- WebP → JPEG 是第二次有损编码，只减不加；能回到原始文件请从原始文件走WebP → JPEG is a second lossy pass and only subtracts; go back to the original file when you have it
- 无损 WebP 的精确像素回到 JPEG 必然消失The exactness of a lossless WebP cannot survive the way back into JPEG
- 动图只出一帧，而且「丢帧」这条提示目前只为 GIF 写——实现只对 GIF 数帧An animation yields one frame, and the “frames lost” notice is currently written only for GIF — the implementation counts frames only there
- 产物不带元数据：画布里只有像素，编码出来的 JPEG 里也只有像素No metadata is carried: the canvas holds pixels and the encoder is handed pixels
实操提示Working with it
- 如果目的只是「更小」，别在两个有损格式之间转手——从原始文件重新编码才划算If the goal is simply “smaller”, do not hand a picture between two lossy formats — re-encoding from the original is the cheaper move
- 输出面板的设置会被记住，同一批的所有文件共用一次读取The panel settings persist and apply to the whole batch from a single read
常见问题Questions people actually ask
为什么透明区域变成一大块白？Why did the transparent area turn into a white block?
JPEG 没有 alpha 通道，必须铺一个不透明底色，本项目铺的是纯白。若白底不合适，请留 WebP 或输出 PNG。JPEG requires an opaque background and has no alpha channel; this route fills pure white. If white is wrong for the picture, keep WebP or output PNG instead.
为什么图比原来糊了一点？Why does it look softer than the original?
因为这是第二次有损编码：WebP 那次已经改过像素，JPEG 这次再改一遍。选更高的质量档能减轻，但换不回已经丢掉的信息。Because this is the second lossy pass: WebP had already changed the pixels and JPEG changes them again. A higher quality step softens the damage but cannot bring back what was already discarded.
动图 WebP 怎么办？What about animated WebP?
栅格化只产出一张静态图，动图会只剩首帧。本项目不能编 GIF，所以「保住动画」这件事不在这条链路的能力范围内。Rasterising produces a still, so the animation ends up as its first frame. The extension cannot encode GIF either, so “keep the animation” is outside what this route can do.
不需要账号，也不需要联网：装好扩展后点图标，在新标签页里打开工作台，文件从磁盘直接选。No account and no network: install the extension, click its icon, and the workbench opens in a new tab reading straight off your disk.
从 Chrome 应用商店安装Install from the Chrome Web Store 安装步骤Install steps GitHub 源码Source on GitHub
要把它压到指定体积？Need it under a target size? The 图片压缩工具image compressor可以在浏览器里重编码 PNG / JPEG / WebP。 re-encodes PNG / JPEG / WebP in the browser.