Merging multiple overlapping transparent png images with php

问题

I have a custom bicycle configurator that layers transparent png files with css. http://www.gallantbicycles.com/build/no1/

I need to add the ability to combine them into one file dynamically so the user can download an image or share it.

This is where I'm at right now, but it results in a black background and only the front most image is seen in the result:

$width = 720;
$height = 500;

$layers = array();
$layers[] = imagecreatefrompng("pathtomyimage/image.png");
$layers[] = imagecreatefrompng("pathtomyimage/image.png");
$layers[] = imagecreatefrompng("pathtomyimage/image.png");

$image = imagecreatetruecolor($width, $height);
imagealphablending($image, false);
imagesavealpha($image, true);

for ($i = 0; $i < count($layers); $i++) {
  imagecopymerge($image, $layers[$i], 0, 0, 0, 0, $width, $height, 100);
}

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

回答1:

You have to replace this code

imagealphablending($image, false);
imagesavealpha($image, true);

for ($i = 0; $i < count($layers); $i++) {
  imagecopymerge($image, $layers[$i], 0, 0, 0, 0, $width, $height, 100);
}

imagealphablending($image, true);
for ($i = 0; $i < count($layers); $i++) {
  imagecopymerge($image, $layers[$i], 0, 0, 0, 0, $width, $height, 100);
}
imagealphablending($image, false);
imagesavealpha($image, true);

imagealphablending must be true in order to correcly stack the layers, but it must be false to save the image.

回答2:

Try this solution: Merge two images with transparencies in PHP

use imagecopyresampled instead of imagecopymerge

回答3:

Here is code which works:

$width = 210;
$height = 190;

$layers = array();
$layers[] = imagecreatefrompng("img/01_boy_faceB.png");
$layers[] = imagecreatefrompng("img/01_boy_hairB.png");

$image = imagecreatetruecolor($width, $height);

// to make background transparent
imagealphablending($image, false);
$transparency = imagecolorallocatealpha($image, 0, 0, 0, 127);
imagefill($image, 0, 0, $transparency);
imagesavealpha($image, true);

/* if you want to set background color
$white = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $white);
*/

imagealphablending($image, true);
for ($i = 0; $i < count($layers); $i++) {
    imagecopy($image, $layers[$i], 0, 0, 0, 0, $width, $height);
}
imagealphablending($image, false);
imagesavealpha($image, true);

imagepng($image, 'final_img.png');

?>

来源：https://stackoverflow.com/questions/18281395/merging-multiple-overlapping-transparent-png-images-with-php

标签

php