Merge 2 transparent PNG images with PHP GD library - php

Question

I am trying to combine two transparent PNG images. The second PNG image should have 50% opacity.
The issue:
If the second PNG covers only the non-transparent pixels of the first PNG, then everything is fine.
If the second PNG has areas which cover the transparent pixels of the first PNG, then these areas become black.
The code:
<?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, $image2, 0, 0, 0, 0, 150, 150, 50);
header('Content-Type: ' . image_type_to_mime_type(IMAGETYPE_PNG));
imagepng($merged_image);
?>

Answer 1

How about if you try this instead? It works for me.
<?php
$image1 = imagecreatefrompng('a.png'); //300 x 300
$image2 = imagecreatefrompng('b.png'); //150 x 150
$merged_image = imagecreatetruecolor(300, 300);
// DEFINE MAGENTA AS THE TRANSPARENCY COLOR AND FILL THE IMAGE FIRST
$transparentColor = imagecolorallocate($merged_image, 255, 0, 255);
imagecolortransparent($merged_image, $transparentColor);
imagefill($merged_image, 0, 0, $transparentColor);
imagesavealpha($merged_image, true);
imagealphablending($image1, false);
imagecopyresampled($merged_image, $image1, 0, 0, 0, 0, 300, 300, 300, 300);
imagealphablending($image1, true);
imagedestroy($image1); // FREE UP SOME MEMORY
imagealphablending($image2, false);
imagecopyresampled($merged_image, $image2, 0, 0, 0, 0, 300, 300, 150, 150);
imagealphablending($image2, true);
imagedestroy($image2); // FREE UP SOME MEMORY
imagealphablending($merged_image, false);
imagesavealpha($merged_image, true);
header('Content-Type: ' . image_type_to_mime_type(IMAGETYPE_PNG));
imagepng($merged_image);
?>
It took me a lot of experimenting in this. I hope this helps you or someone else who may stumble upon this.