#!/bin/bash

# author : jiangxf 2015.1.21

if [ $# -lt 2 ]; then
    echo "Usage: resizePng.sh {pngName} {percentage}";
    exit;
fi

width=`sips -g pixelHeight $1 | tail -n1 | awk -F: '{print $2}'`

newWidth=`expr $width \* $2 / 100`;

echo "$1: width($width => $newWidth)";

sips -Z $newWidth $1; 

用法

find . -name "*.png" -exec ./resizePng.sh {} 67 \;