준비

$ brew install imagemagick

스크립트

#!/bin/bash

CAP_FRAME_NUM=10
CAP_INTERVAL_SEC=1
CAP_POS_X=0
CAP_POS_Y=0
CAP_WIDTH=200
CAP_HEIGHT=200

GIF_FRAME_INTERVAL_MSEC=100
GIF_WIDTH=$CAP_WIDTH
GIF_HEIGHT=$CAP_HEIGHT

# `screencapture`コマンドで指定範囲の画面キャプチャを指定秒間隔で生成
for i in `seq -w 1 ${CAP_FRAME_NUM}`; do
    screencapture -R ${CAP_POS_X},${CAP_POS_Y},${CAP_WIDTH},${CAP_HEIGHT} -m frame_${i}.png
    sleep ${CAP_INTERVAL_SEC}
done

# 画面キャプチャ画像群をImageMagickでGIFアニメーションに変換
convert -delay ${GIF_FRAME_INTERVAL_MSEC} -loop 0 frame_*.png -resize ${GIF_WIDTH}x${GIF_HEIGHT} animation.gif

GIF 예