for mac

android_screen_cap_and_resize.sh

#!/bin/sh                                                                                                                                                                          

SAVE_DIR=./screenshot
FILE_PATH=$SAVE_DIR/`date +%Y%m%d%H%M%S`.png
TMP_FILE=/sdcard/ss.pn

# capture screen image                                                                                                                                                               
mkdir -p $SAVE_DIR 2>/dev/null
adb shell screencap -p $TMP_FILE
adb pull $TMP_FILE $FILE_PATH
adb shell rm $TMP_FILE

# resize image                                                                                                                                                                  
sips -Z	320 $FILE_PATH