PHP- Put individual images into a transparent canvas - php

Question

I'm creating a simple php sprite image generator, I was able to calculate the possible width and height of the sprite image, but I'm stuck at creating the transparent canvas and put the images into it.
Now let's say the width of the sprite image is 200x500px (i'm creating vertical sprite). And the images to put in the sprite image is in an array like so:
array('logo.png','delete.png','open.png');
How you gonna put those images into the sprite?

Answer 1

$path = '/img/';
$imgs = array('logo.png','delete.png','save.png');//images needed to be put in the sprite
$canvasWidth= 0;
$canvasHeight = 0;
//calculate the posible canvas width and height
foreach($imgs as $val)
{
$info = getimagesize($path.basename($val));
$width=$info[0];
$height=$info[1];
$canvasHeight +=$height;
if($canvasWidth < $width){
$canvasWidth = $width;
}
}
// create our canvas
$img = imagecreatetruecolor($canvasWidth, $canvasHeight);
$background = imagecolorallocatealpha($img, 255, 255, 255, 127);
imagefill($img, 0, 0, $background);
imagealphablending($img, false);
imagesavealpha($img, true);
// start placing our icons from the top down.
$pos = 0;
foreach($imgs as $val){
$tmp = imagecreatefrompng($path.basename($val));
$w=imagesx($tmp);
$h=imagesy($tmp);
imagecopy($img, $tmp, 0, $pos, 0, 0, $w, $h);
$pos += $h;
imagedestroy($tmp);
}
// create our final output image.
imagepng($img, $path.'sprite.png');