How to preserve transparency in PHP GD on a PNG - php

Question

I am using this code:
<?php
list($width, $height, $type, $attr) = getimagesize("terrain.png");
$canvas = imagecreatetruecolor($width, $height);
$src = imagecreatefrompng("terrain.png");
if($_GET['glass'] == 1){
$src2 = imagecreatefrompng("rock.png");
}
imagecopymerge($canvas, $src, 0, 0, 0, 0, $width, $height, 100);
if($_GET['glass'] == 1){
imagecopy($canvas, $src2, 0, 0, 0, 0, 16, 16);
}
imagealphablending($canvas, true);
imagesavealpha($canvas, true);
header("Content-type: image/png");
imagepng($canvas);
imagedestroy($dest);
imagedestroy($src);
?>
Terrain.png is at http://hogofwar.co.uk/experiment/mc/terrain.png (which is transparent)
How do I preserve the transparency when using GD?

Answer 1

You can try
Parameters:
$new_image = image resource identifier such as returned by imagecreatetruecolor(). must be passed by reference
$image_source = image resource identifier returned by imagecreatefromjpeg, imagecreatefromgif and imagecreatefrompng. must be passed by reference
<?php
function setTransparency($new_image,$image_source)
{
$transparencyIndex = imagecolortransparent($image_source);
$transparencyColor = array('red' => 255, 'green' => 255, 'blue' => 255);
if ($transparencyIndex >= 0) {
$transparencyColor = imagecolorsforindex($image_source, $transparencyIndex);
}
$transparencyIndex = imagecolorallocate($new_image, $transparencyColor['red'], $transparencyColor['green'], $transparencyColor['blue']);
imagefill($new_image, 0, 0, $transparencyIndex);
imagecolortransparent($new_image, $transparencyIndex);
}
?>
You can check for more details,
http://www.php.net/manual/en/function.imagecolortransparent.php

Answer 2

Try this:
$img = imagecreatefrompng("yourimage.png");
$width = imagesx($img);
$height = imagesy($img);
$new_width=500;//this is the new width of the output image
$newheight=($height/$width)*$new_width;
$target=imagecreatetruecolor($new_width,$newheight);
$transparent=imagecolorallocatealpha($target,0,0,0,127);
imagefill($target,0,0,$transparent);
imagecopyresampled($target,$img,0,0,0,0,$new_width,$newheight,$width,$height);
imagealphablending($target,false);
imagesavealpa($target,true);
imagepng($target,"your_target_filename.png");
Done...