Watermaking Images

Rendair · 12-19-2007, 03:04 PM

Hey all, time for another GD tutorial. This time i am going to go through "watermarking" your images.

DEMO: HERE

Firstly create a watermark image and save it as png-24 for best quality.

Firstly of course we want to set the actual image we want to watermark.

PHP Code:


			
$file = $_GET["src"]; // set it to a variable

That will take the source of the image from a variable set in the url, which we will talk about later.

Next we want to create the watermark image and load it up into RAM.

PHP Code:


			
$watermark = imagecreatefrompng("watermark.png");

As i said PNG work best. We do have a problem with using PNG-24 as the new GD doesnt seem to like it. Usally it just gives the image a white background, but we can get around this by doing the following.

PHP Code:


			
imagealphablending($watermark, true);

Now we want to create the actual image we are adding the watermark to and load it into RAM.

PHP Code:


			
$image=imagecreatefromjpeg($file);

Now we just want to get the height and width of the image so we can place the watermark correctly.

PHP Code:


			
$imageWidth=imageSX($image);

$imageHeight=imageSY($image);

and we also want to do the same for the actual watermark image itself.

PHP Code:


			
$watermarkWidth=imageSX($watermark);

$watermarkHeight=imageSY($watermark);

Now we need to set up some variables that will tell us where to place the watermark on the image.

PHP Code:


			
$coordinate_X = ($imageWidth - 5) - ($watermarkWidth);

$coordinate_Y = ($imageHeight - 5) - ($watermarkHeight);

//we want to be at least 5 pixels from the edge, but to make sure

// we shall add abit more so also take away the watermark dimensions

Now its a matter of place the watermark on the actual image.

PHP Code:


			
imagecopy($image, $watermark, $coordinate_X, $coordinate_Y, 0, 0, $watermarkWidth, $watermarkHeight);

Now we need to set a header type as a image as we do with all GD scripts and also display the image, but also clear any information we may still have in the RAM.

PHP Code:


			
header('content-type: image/jpeg'); 

imagejpeg ($image);

imagedestroy($image);

imagedestroy($watermark);

Usage

This script can easily be used by using the following script.

PHP Code:


			
<img src=watermark.php?src=image.jpg>

//change the image.jpg with the location of the image you want to

//watermark

And there you go a nicely watermarked image

FULL CODE

PHP Code:


			
<?php



    $file = $_GET["src"];

    $watermark = imagecreatefrompng("watermark.png");

    

    imagealphablending($watermark, true);



    $image=imagecreatefromjpeg($file);



    $imageWidth=imageSX($image);

    $imageHeight=imageSY($image);



    $watermarkWidth=imageSX($watermark);

    $watermarkHeight=imageSY($watermark);



    $coordinate_X = ($imageWidth - 5) - ($watermarkWidth);

    $coordinate_Y = ($imageHeight - 5) - ($watermarkHeight);



    imagecopy($image, $watermark, $coordinate_X, $coordinate_Y, 0, 0, $watermarkWidth, $watermarkHeight);

    

    header('content-type: image/jpeg'); 

    imagejpeg ($image);

    imagedestroy($image);

    imagedestroy($watermark);



?>

This only currently creates watermarks for jpegs, but can easily be changed to support all types.