Image watermarking in php

I want to watermark an image and save it. here is the code i am using for it. Here it is outputting the image and is storing that output to the file. I want to save it without outputting it.

// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefrompng('stamp.png');
$im = imagecreatefromjpeg('proverbs.jpeg');

// Set the margins for the stamp and get the height/width of the stamp image
$marge_right = 10;
$marge_bottom = 10;
$sx = imagesx($stamp);
$sy = imagesy($stamp);

// Copy the stamp image onto our photo using the margin offsets and the photo 
// width to calculate positioning of the stamp. 
  imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy -   $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp));

// Output and free memory
header('Content-type: image/png');
ob_start();
// output jpeg (or any other chosen) format & quality
imagejpeg($im, NULL, 85);
// capture output to string
$contents = ob_get_contents();
// end capture
ob_end_clean();
//imagepng($im);
imagedestroy($im);
$f开发者_JAVA百科h = fopen("proverbs.jpeg", "w" );
fwrite( $fh, $contents );
fclose( $fh );

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Saving it to a file?

Simply change

imagejpeg($im, NULL, 85);

to

imagejpeg($im, 'image.jpg', 85);