Ridimensionamento Immagini PNG... sfondo nero

[cubalibre810]

Prova sostituendo

$dst_img = ImageCreateTrueColor($thumb_w, $thumb_h);

imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w, $thumb_h,$old_x, $old_y); 

con

$dst_img = imagecreatetruecolor($thumb_w, $thumb_h);
imagealphablending($dst_img, false);

imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w, $thumb_h,$old_x, $old_y);
imagesavealpha($dst_img, true);