Image Automatic Watermarking.

[killerchutney]

Hi, Does anyone know of any free Automatic image watermarking that I can implement into a image uploading script.

Thanks.

[mburt]

Use CSS:

background:url('myimage.jpg') no-repeat fixed top left;
If you want to give it a "watermark" effect, use an image-editing program.

[killerchutney]

Thanks for quick reply but is it possible for PHP to get an image, put a watermark over it so its only one image. I think it is because PHP can create captcha codes on the fly.

[mburt]

Look in the php.net manual (image functions):
http://ca3.php.net/manual/en/ref.image.php

[boxxertrumps]

GD library.
http://www.phpfreaks.com/tutorials/105/0.php

[djr33]

You should be able to combine two images fairly easily.

Create a loop that runs through all of the pixels, then for each that is white in the watermark image, make the pixel of the main image a blend of the watermark pixel and image pixel. If black, leave as is. Or any variation you want.


Basically, something like--


<?php
$imgurl = $_GET['img'];
$image=imageCreateFromJPEG($imgurl);
//or create your image from upload

$imagewidth = imagesx($image);
$imageheight = imagesy($image);
//get dimensions

$watermarkurl = $_GET['wm'];
$watermark=imageCreateFromGIF($watermarkurl);
//as above, do what you want for getting the watermark

$wmwidth = imagesx($watermark);
$wmheight = imagesy($watermark);
//get dimensions of watermark

imagecopyresampled($watermark, $watermark, 0, 0, 0, 0, $imagewidth, $imageheight, $wmwidth, $wmheight);
//resize the watermark to be in the same dimensions as the image

for ($y = 0; $y < $imageheight; $y++) {
for ($x = 0; $x < $imagewidth; $x++) {
$imgcolor = imagecolorat($image,$x,$y);
$imgcolorrgb = imagecolorsforindex($image,$imgcolor);
$ir = $imgcolorrgb['red'];
$ig = $imgcolorrgb['green'];
$ib = $imgcolorrgb['blue'];
$wmcolor = imagecolorat($watermark,$x,$y);
$wmcolorrgb = imagecolorsforindex($watermark,$wmcolor);
$wr = $wmcolorrgb['red'];
$wg = $wmcolorrgb['green'];
$wb = $wmcolorrgb['blue'];
if ($ir<$wr&&$ig<$wg&&$ib<$wb) {
$pxcolor = imagecolorallocate($image, ($ir+$wr)/2, ($ig+$wg)/2, ($ib+$wb)/2);
imagesetpixel($image, $x, $y, $pxcolor);
}
}
}
//loop through image
//and set pixel to white
//if wm is white at pixel

header("Content-type: image/jpg");
imagejpeg($image);
imagedestroy($image);
//output
?>

[boxxertrumps]

Does gd library support layers?

if so, a semitransperent png ontop of the watermarked picture would be the best option.

[djr33]

Its support for layers is annoying and not very trustworthy.

Anyway, I've been testing, and here's the result:

http://ci-pro.com/misc/phptest/images/watermark.php?img=http://www.huddletogether.com/projects/lightbox/images/image-1.jpg&wm=http://www.informika.ru/text/magaz/higher/Image25.gif
From two random sources:
http://www.huddletogether.com/projects/lightbox/images/image-1.jpg
http://www.informika.ru/text/magaz/higher/Image25.gif

Note: The code in the last post is updated to reflect changes I made.

[tech_support]

It's a bit laggy though.

[djr33]

Sure. It's running through every pixel.

This is for watermarking on upload, so it shouldn't be an issue.

Write a faster script if you question this :D
...PHP is slow with images, but I have yet to find a way around that.

[tech_support]

Ok.

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