php imagick function sets the picture background to be transparent

$image = new Imagick('1.png');
$image->borderImage(new ImagickPixel("white"),1,1);
$image->paintfloodfillimage('transparent',2000,NULL,0,0);
$draw = new ImagickDraw();
$draw->color(0,0,imagick::PAINT_FLOODFILL);
$image->drawImage($draw);
$image->shaveImage(1,1);
header("Content-Type: image/{$image->getImageFormat()}");
echo $image->getImageBlob( );
//$image->writeImage('o.png');
$image->clear();
$image->destroy();
?>

源图片：

效果图：