Merge two PNG images with PHP GD library

Question

Does anybody have a script which can merge two PNG images?

With the following conditions:

• Both images have transparent areas
• The second image must have 50% opacity (it is overlaid over the first image)

Here is what I tried to do but without luck:

<?php

function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct){ 
    $cut = imagecreatetruecolor($src_w, $src_h);
    imagecopy($cut, $dst_im, 0, 0, $dst_x, $dst_y, $src_w, $src_h); 
    imagecopy($cut, $src_im, 0, 0, $src_x, $src_y, $src_w, $src_h); 
    imagecopymerge($dst_im, $cut, $dst_x, $dst_y, 0, 0, $src_w, $src_h, $pct); 
}

$image1 = imagecreatefrompng('a.png'); //300 x 300
$image2 = imagecreatefrompng('b.png'); //150 x 150

$merged_image = imagecreatetruecolor(300, 300);
imagealphablending($merged_image, false);
imagesavealpha($merged_image, true);

imagecopy($merged_image, $image1, 0, 0, 0, 0, 300, 300);
imagecopymerge_alpha($merged_image, $image2, 0, 0, 0, 0, 150, 150, 50);

header('Content-Type: image/png');
imagepng($merged_image);

?>

Edit:

• First Image (left) and Second Image (right)

• This is how it should be (left) and the result of my code (right)

• The result of the solution proposed by dqhendricks

Solution 1

$image1 = imagecreatefrompng('a.png'); //300 x 300
$image2 = imagecreatefrompng('b.png'); //150 x 150
imagecopymerge($image1, $image2, 0, 0, 75, 75, 150, 150, 50);

this should be all you need. $image1 should hold the merged image where image2 has been overlayed with 50% opacity. the last argument is the alpha of the merged copy.

http://php.net/manual/en/function.imagecopymerge.php

Solution 2

$merged_image = imagecreatetruecolor(300, 300);
imagealphablending($merged_image, false);
imagesavealpha($merged_image, true);

imagecopy($merged_image, $image1, 0, 0, 0, 0, 300, 300);
// after first time of "imagecopy" change "imagealphablending"
imagealphablending($merged_image, **true**);

imagecopy($merged_image, $image2, 0, 0, 0, 0, 300, 300);

Comments

[acoder]

As per your suggestion i used imagecopymerge($image1, $image2, 0, 0, 0, 0, 150, 150, 50); i posted the result image in Issue Description.

[dqhendricks]

can you run php.net/manual/en/function.imageistruecolor.php on both image1 and image 2 to verify that they are loaded as truecolor images?

[acoder]

PHP Version 5.2.17 GD Version bundled (2.0.34 compatible)

[acoder]

Yes, the result of imageistruecolor is 1 for both image1 and image2.

[dqhendricks]

@acoder apparently there is an open bug for this: bugs.php.net/bug.php?id=23815

[dqhendricks]

@acoder I found a way to do this the other day. you need to set alpha blending and save alpha on the $cut image before doing the copies.