pngdefy可以将Xcode中pngcrush处理过的png图片进行还原
ImageMagick可以通过命令对图片进行处理
具体见
GitHub

#输入主图片，如AppIcon.png（1024*1024）
BASEIMAGE=$1{
#获取文件名称，去除后缀
FILENAME=${BASEIMAGE%.*}

function generateIcon () {   
      #拷贝图片后，重新命名，pngdefry进行解析, 并转化为指定的3x  
      fileName=${FILENAME}$1x$1@3x.png   
      cp ${BASEIMAGE} ${fileName}   
      ./pngdefry -o ./    ${fileName}    
  
      #计算尺寸   
      size=`expr 3 \* $1`    
      convert ${fileName} -resize ${size}x${size} ${fileName}    
      convert betaRibbon.png -resize ${size}x${size} resizedBetaRibbon.png   
      composite   resizedBetaRibbon.png ${fileName} ${fileName}   

       #2x  
       fileName=${FILENAME}$1x$1@2x.png    
       cp ${BASEIMAGE} ${fileName}    
      ./pngdefry -o ./    ${fileName}    
      size=`expr 2 \* $1`   
      convert ${fileName} -resize ${size}x${size} ${fileName}   
      convert betaRibbon.png -resize ${size}x${size} resizedBetaRibbon.png    
      composite resizedBetaRibbon.png ${fileName} ${fileName}
}
    echo "##generateIcon 60x60"generateIcon "60"
    echo "##generateIcon 29x29"generateIcon "29"
    echo "##generateIcon 40x40"generateIcon "40"
    echo "##generateIcon 57x57"generateIcon "57"}