public function actionGetpicture()
 {  
    $request = Yii::$app->request;
   $sourcePic=$request->post('sourcePic');
   $maskPic=$request->post('maskPic'); 
   $cropPicName=$request->post('cropPicName'); 
 
   // $sourcePic="http://bings.local.com/bi_ngs2_2/assets/images/yinpian1/page2Bg4.png";
   // $maskPic="http://bings.local.com/bi_ngs2_2/assets/images/jinmao.png";
   $source = imagecreatefrompng( $sourcePic );
   $mask = imagecreatefrompng( $maskPic); 
   // Apply mask to source
   // imagealphamask( $source, $mask );
   $this->imagealphamask ($source, $mask );
   // Output
   header( "Content-type: image/png"); 
   // 生成截取后的图片并保存在本地
   imagepng( $source,"assets/images/crop/".$cropPicName.".png" );
   //销毁图片内存
   imagedestroy($source);
      
 }
 
 public function imagealphamask( &$picture, $mask ) {
   // Get sizes and set up new picture
   $xSize = imagesx( $picture );
   $ySize = imagesy( $picture );
   $newPicture = imagecreatetruecolor( $xSize, $ySize );
   imagesavealpha( $newPicture, true );
   imagefill( $newPicture, 0, 0, imagecolorallocatealpha( $newPicture, 100, 100, 0, 127 ) );
 
   // Resize mask if necessary
   // if( $xSize != imagesx( $mask ) || $ySize != imagesy( $mask ) ) {
   //   $tempPic = imagecreatetruecolor( $xSize, $ySize );
   //   imagecopyresampled( $tempPic, $mask, 0, 0, 0, 0, $xSize, $ySize, imagesx( $mask ), imagesy( $mask ) );
   //   imagedestroy( $mask );
   //   $mask = $tempPic;
   // }
 
   // Perform pixel-based alpha map application
   for( $x = 0; $x < $xSize; $x++ ) {
     for( $y = 0; $y < $ySize; $y++ ) {
       $alpha = imagecolorsforindex( $mask, imagecolorat( $mask, $x, $y ) );
       //small mod to extract alpha, if using a black(transparent) and white
       //mask file instead change the following line back to Jules's original:
       // $alpha = 127 - floor($alpha['black'] / 2);
       //or a white(transparent) and black mask file:
       // $alpha = floor($alpha['black'] / 2);
       $alpha = $alpha['alpha'];
       $color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) );
       //preserve alpha by comparing the two values
       if ($color['alpha'] > $alpha)
         $alpha = $color['alpha'];
       //kill data for fully transparent pixels
       if ($alpha == 127) {
         $color['red'] = 0;
         $color['blue'] = 0;
         $color['green'] = 0;
       }
       imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, $color[ 'red' ], $color[ 'green' ], $color[ 'blue' ], $alpha ) );
     }
   }
 
   // Copy back to original picture
   imagedestroy( $picture );
   $picture = $newPicture;
 }