html2canvas($(".head1pic"), {
     onrendered: function(canvas) { 
     url = canvas.toDataURL("image/png", 1.0);
       sourcePic = "assets/images/demo.png";
       maskPic = "assets/images/jinmao.png";
          cropPicName = "cropDog1";
          // ajax php截图
          $.ajax({
          type: 'post',
           url: 'getpicture',
          data: {
            "sourcePic": sourcePic,
            "maskPic": maskPic,
            "cropPicName": cropPicName
            },
         success: function(data) {
             $(".page2Bg")[0].setAttribute("src", "assets/images/crop/cropDog1.png"); 
            },
         error: function(data) {
              console.log(data)
              }
            });
       }
 });

 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;
  }