离线 · 无上传 · 浏览器本地完成Offline · no uploads · runs in the browser
WebP 转 PNG——透明保留，本地重编码WebP to PNG offline — transparency kept
WebP 省带宽，但不是每个编辑器、印刷流程或旧系统都收。这条路径把图片解码到 `<canvas>`，再编码成 PNG：PNG 分支不铺白底，所以带透明度的 WebP 转过去仍然是透明背景。解码后若最长边超过 8192 px 会先等比缩小（浏览器画布的单边上限），输出面板里的“最长边”也会在这一步生效；PNG 是无损容器，质量与目标体积两个参数对它不作用。WebP saves bandwidth, but not every editor, print pipeline or legacy system accepts it. This route decodes the image into a `<canvas>` and encodes PNG: the PNG branch adds no white fill, so a WebP with transparency stays transparent. If the long edge exceeds 8192 px after decoding it is scaled down proportionally first (the browser’s per-side canvas ceiling), and the “max edge” output setting applies at this step too. PNG is lossless, so the quality and target-size levers do not act on it.
这条链路怎么走How the route runs
WebPWebP PNGPNG
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
- 像素内容按原分辨率重编码（除非触发 8192 px 单边上限，或你设置了更小的最长边）Pixels are re-encoded at the original resolution unless the 8192 px per-side ceiling or a smaller max-edge setting applies
- 透明通道保留：PNG 分支不铺白底，alpha 原样写进产物Transparency is kept: the PNG branch adds no white fill, so alpha is written through
- 批量：一批最多 200 个文件、单个 100 MB，可一次转完Batch: up to 200 files per batch and 100 MB per file
- 图片输出参数里的最长边对这条路径生效The max-edge output setting takes effect on this route
如实说明的限制What it does not do
- 动图 WebP 只画第一帧：`drawImage` 只取一帧，而多帧检测只覆盖 GIF，所以这条路径不会为动图 WebP 单独给出丢帧提示Animated WebP keeps the first frame only: `drawImage` takes one frame, while multi-frame detection covers GIF alone, so this route gives no lost-frame notice for an animated WebP
- 重编码会改变字节：这是解码再编码，不是容器换壳；无损 PNG 通常比原 WebP 大，差距取决于画面Re-encoding changes the bytes: this is decode-then-encode, not a container swap; a lossless PNG is usually larger than the source WebP
- EXIF 方向、ICC 配置等元数据不随 canvas 走；浏览器解码时已按方向摆正，但其它元数据不会写回Metadata such as EXIF orientation and ICC profiles does not travel through the canvas; orientation is already applied at decode time, but the other fields are not written back
- 被 8192 px 上限缩过的图无法从产物里恢复原尺寸An image scaled down by the 8192 px ceiling cannot be restored from the result
实操提示Working with it
- 要保留动画，这条路径不对：它只取首帧。反过来，PNG → WebP 也走同一条画布路径This route is not for keeping animation: it takes the first frame. In the other direction, PNG → WebP takes the same canvas path
- 同一张图还能转 JPEG（透明会被白底取代）或 PDF（一页一图）；尺寸与格式的取舍各自写在对应页The same image can go to JPEG (transparency replaced by white) or PDF (one image per page); each page spells out its own trade-offs
常见问题Questions people actually ask
透明背景会变白吗？Will the transparent background turn white?
不会。转 PNG 的分支不铺白底，alpha 通道保留。只有目标是 JPEG 时才会先铺白，因为 JPEG 没有透明通道。No. The PNG branch adds no white fill and keeps the alpha channel. White is laid down only for a JPEG target, which has no alpha channel.
为什么转出来的 PNG 比 WebP 大？Why is the PNG larger than the WebP?
因为这是一次完整的解码再编码，不是改扩展名。WebP 用有损或更高效的压缩，PNG 是无损容器；画面越复杂，差距越明显。Because this is a full decode and re-encode, not a renamed file. WebP uses lossy or more efficient compression while PNG is a lossless container; busier images widen the gap.
我的图超过 8192 像素会怎样？What if my image is larger than 8192 pixels?
浏览器单边画布上限是 8192 px，超过时按比例缩到上限再编码；你也可以在输出参数里把最长边设得更小。需要原尺寸时请先确认原图尺寸，产物不会标注它被缩过。The browser’s per-side canvas ceiling is 8192 px; anything larger is scaled down proportionally before encoding, and you can set a smaller max edge in the output options. Check the source dimensions first if you need full size — the result does not label itself as downscaled.
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.