PHP/Graphics Image/imagecolorallocatealpha

Using imagecolorallocatealpha

 
<?php
        define("WIDTH", 300);
        define("HEIGHT", 300);
        $img = imagecreatetruecolor(WIDTH, HEIGHT);
        $white = imagecolorallocate($img, 0xFF, 0xFF, 0xFF);
        $yellow = imagecolorallocate($img, 0xFF, 0xFF, 00);
        $red = imagecolorallocate($img, 0xFF, 0, 0);
        $blue_t   = imagecolorallocatealpha($img, 0, 0, 0xFF, 0x40);
        imagefill($img, 1, 1, $white);
        imageline($img, 0,0, WIDTH-1, HEIGHT-1, $blue_t);
        imagefilledrectangle($img, (WIDTH/2)-50, (HEIGHT/2)-50,(WIDTH/2)+50, (HEIGHT/2)+50, $yellow);
        header("Content-Type: image/png");
        imagepng($img);
?>