PHP GD imagecolorallocatealpha only makes grey text - php

Question

Is there any reason why imagecolorallocatealpha() would only be making the text grey?
<?php
header('Content-Type: image/png');
function checkImg($imgname) {
$im = #imagecreatefrompng($imgname);
if(!$im) {
$im = imagecreatetruecolor(150, 30);
$bgc = imagecolorallocate($im, 255, 255, 255);
$tc = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 150, 30, $bgc);
imagestring($im, 1, 5, 5, 'Error loading ' . $imgname, $tc);
}
return $im;
}
$hr = 48;
$tOne = "VALID FOR";
$tTwo = $hr." HOURS";
$img = checkImg('img.png');
$font = 'helr67w.ttf';
$size = 9;
$red = imagecolorallocatealpha($img, 255, 0, 0, 75);
imagettftext($img, $size, 0, 225, 132, $red, $font, $tOne);
imagettftext($img, $size, 0, 225, 144, $red, $font, $tTwo);
imagepng($img);
imagedestroy($img);
?>

Answer 1

In your code you don't set the image to support an alpha channel. I can imagine that is causing the issue:
function checkImg($imgname) {
$im = #imagecreatefrompng($imgname);
if(!$im) {
$im = imagecreatetruecolor(150, 30);
$bgc = imagecolorallocate($im, 255, 255, 255);
$tc = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 150, 30, $bgc);
imagestring($im, 1, 5, 5, 'Error loading ' . $imgname, $tc);
}
// Turn off alpha blending and set alpha flag
imagealphablending($im, true);
imagesavealpha($im, true);
return $im;
}
See imagesavealpha PHP Manual and imagealphablending PHP Manual