离线 · 无上传 · 浏览器本地完成Offline · no uploads · runs in the browser
GIF 转 JPEG——首帧、白底、本地完成GIF to JPEG offline — first frame on white
GIF 常被当成“会动的图片”，但很多接收方只想要一张静态封面。这条路径用 `<img>` 解码出第一帧，画到画布上，再编码成 JPEG。JPEG 没有 alpha 通道，所以编码前会先铺满白底——这不是丢像素，而是把透明区域按白纸处理。若输入确实是多帧 GIF（按块结构数到第二个 image descriptor 就判定），结果会带上丢帧标记，界面里明确写出“其它帧没有保留”，而不是悄悄交出一张静帧。A GIF is often used as “the moving picture”, while the recipient just wants a still cover. This route decodes the first frame through `<img>`, draws it to a canvas and encodes JPEG. JPEG has no alpha channel, so the canvas is filled white first — not lost pixels, but treating transparent areas as white paper. If the input really has more than one frame (the block structure is walked until a second image descriptor appears), the result carries a lost-frames flag and the UI says so instead of quietly handing back a still.
这条链路怎么走How the route runs
GIFGIF 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
- 第一帧的全部像素，按原尺寸重编码（触发 8192 px 单边上限时等比缩小）Every pixel of the first frame, re-encoded at the original size unless the 8192 px per-side ceiling applies
- 透明区域按白底落地，颜色不串到别的像素Transparent areas land on white, with no colour bleeding into other pixels
- 多帧 GIF 的丢帧会在结果里标记，界面如实披露A multi-frame GIF carries a lost-frames flag, surfaced in the UI
- JPEG 的质量、目标体积与最长边参数在这条路径上生效；一批最多 200 个文件Quality, target size and max edge apply on this route; up to 200 files per batch
如实说明的限制What it does not do
- 动画不会保留：产物是一张静态 JPEG。需要动图时不要走这条Animation is not kept: the result is a still JPEG, so do not take this route for a moving image
- 透明丢失：alpha 被白底取代，半透明像素会与白色混合Transparency is lost: alpha is replaced by white, and semi-transparent pixels blend with it
- JPEG 有损：反复转换会累积压缩损失JPEG is lossy, so repeated conversions accumulate compression loss
- 多帧检测只覆盖 GIF；APNG 与动图 WebP 不在这条路径的检测范围内，但它们同样只会走一帧Multi-frame detection covers GIF only; APNG and animated WebP are outside its scope here, though they too contribute a single frame
实操提示Working with it
- 想要透明背景就别选 JPEG：GIF → PNG 保留 alpha，只有确实需要 JPEG 时才接受白底For a transparent background, do not pick JPEG: GIF → PNG keeps alpha, and white is only the price of genuinely needing JPEG
- GIF 还能直接铺成一页 PDF（一页一图、无文字层）；那条同样披露丢帧A GIF can also become a one-page PDF (one image per page, no text layer); that route discloses the lost frames as well
常见问题Questions people actually ask
为什么只剩一帧？Why do I get a single frame?
静态 JPEG 存不下时间轴。浏览器在这里通过 `<img>` 只解码第一帧；工具会先判断 GIF 是否真的多帧，是的话在结果里标记丢帧，避免把“静帧”当成完整转换。A still JPEG has nowhere to store a timeline. The browser decodes the first frame through `<img>`; the tool first checks whether the GIF really has multiple frames and flags the loss when it does, rather than presenting a still as the complete conversion.
透明背景去哪了？Where did the transparency go?
被白底取代了。JPEG 没有透明通道，编码前画布会填满白色；半透明像素会与白色混合。要保留透明，请选 GIF → PNG。It was replaced by white. JPEG has no alpha channel, so the canvas is filled white before encoding and semi-transparent pixels blend with it. To keep transparency, choose GIF → PNG.
质量参数会生效吗？Do the quality settings apply?
会。JPEG 是这条路径最终写出的格式，输出参数里的质量、目标体积与最长边都在最后编码时生效。Yes. JPEG is the format this route finally writes, so quality, target size and max edge from the output settings all act at the final encode.
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.