I'm attempting to resize pngs with transparent backgrounds in PHP and the code samples I've found online don't work for me. Here's the code I'm using, advice will be much appreciated!
$this->image = imagecreatefrompng($filename);
$newImage = imagecreatetruecolor($width, $height);
// Make a new transparent image and turn off alpha blending to keep the alpha channel
$background = imagecolorallocatealpha($newImage, 255, 255, 255, 127);
imagecopyresampled($newImage, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $newImage;
From what I can tell, you need to set the blending mode to
false, and the save alpha channel flag to
true before you do the imagecolorallocatealpha()
<?php $newImg = imagecreatetruecolor($nWidth, $nHeight); imagealphablending($newImg, false); imagesavealpha($newImg,true); $transparent = imagecolorallocatealpha($newImg, 255, 255, 255, 127); imagefilledrectangle($newImg, 0, 0, $nWidth, $nHeight, $transparent); imagecopyresampled($newImg, $im, 0, 0, 0, 0, $nWidth, $nHeight, $imgInfo, $imgInfo); ?>
UPDATE : This code is working only on background transparent with opacity = 0. If your image have 0 < opacity < 100 it'll be black background.