auto crop images in one-line command in Linux

常用小工具集合：

将本文件夹下的 pdf 文档转换成相应的 jpg 格式，像素 600 px/in

for A in *.pdf; do convert -density 600 "$A" "${A%%.}.jpg"; done

(Mainly for personal future reference,) using ImageMagick:

convert -trim image.jpg image.jpg

To trim/autocrop the whole directory: 自动裁剪

for a in *.jpg; do convert -trim "$a" "$a"; done

Or using find:

find -name "*.jpg" -exec convert -trim "{}" "{}" \;

Ref
1. https://superuser.com/questions/216177/command-line-to-automatically-crop-an-image

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