问题
OK. I have a horizontal image, let's say 2000 x 300. I want to overwrite that image and create a new one that is 2000 x 2000 with the old image center in the middle and vertically, with white space around it. I also want to do this in batch with many different images of different sizes. Thanks in advance.
回答1:
Use -resize to resize the image to 2000x2000, -background to set the background to white, -gravity to center the original image on the canvas, and -extent to resize the canvas itself (to cause the image to sit in the centre if it wasn't square originally).
convert [imagename] -resize 2000x2000 -background white \
-gravity center -extent 2000x2000 [imagename]
来源：https://stackoverflow.com/questions/8793777/how-do-i-batch-resize-all-images-to-sqares-with-image-magick