php GD create a transparent png image

Question

I'm trying to create a transparent png image and layer various other pngs and jpgs to create a final png with transparency. I'm having trouble creating my initial empty transparent png. It currently has a white background.

Can anyone point me in the right direction. This is my code so far...

$image = imagecreatetruecolor(485, 500);
imagealphablending($image, false);
imagesavealpha($image, true);
$col=imagecolorallocatealpha($image,255,255,255,127);
imagefill($image, 0, 0, $col);
//imagefilledrectangle($image,0,0,485, 500,$col);


/* add door glass */
$img_doorGlass = imagecreatefrompng("glass/$doorStyle/$doorGlass.png");     
imagecopyresampled($image, $img_doorGlass, 106, 15, 0, 0, 185, 450, 185, 450);              


/* add door */
$img_doorStyle = imagecreatefrompng("door/$doorStyle/$doorStyle"."_"."$doorColor.png");     
imagecopyresampled($image, $img_doorStyle, 106, 15, 0, 0, 185, 450, 185, 450);


$fn = md5(microtime()."door_builder").".png";

if(imagepng($image, "user_doors/$fn", 1)){
  echo "user_doors/$fn";
}       
imagedestroy($image);       

Telepathist

does the change in blending mode help? Don't have the images to test myself, but it would seem that the png images should blend. Otherwise the image is created just as per php docs and user-contributed notes, so can't see the problem there, sorry – Satirist

Answer 1

Set imagealphablending($image,true); on each new layer.

Try this:

<?php
$image = imagecreatetruecolor(485, 500);
imagealphablending($image, false);
$col=imagecolorallocatealpha($image,255,255,255,127);
imagefilledrectangle($image,0,0,485, 500,$col);
imagealphablending($image,true);

/* add door glass */
$img_doorGlass = imagecreatefrompng("glass/$doorStyle/$doorGlass.png");
imagecopyresampled($image, $img_doorGlass, 106, 15, 0, 0, 185, 450, 185, 450);
imagealphablending($image,true);

/* add door */
$img_doorStyle = imagecreatefrompng("door/$doorStyle/$doorStyle"."_"."$doorColor.png");
imagecopyresampled($image, $img_doorStyle, 106, 15, 0, 0, 185, 450, 185, 450);
imagealphablending($image,true);

$fn = md5(microtime()."door_builder").".png";

imagealphablending($image,false);
imagesavealpha($image,true);
if(imagepng($image, "user_doors/$fn", 1)){
    echo "user_doors/$fn";
}
imagedestroy($image);

?>

Nevis

not 100% sure why, but this works. thanks for your help Lawrence – Telepathist

np, it works because imagealphablending($image,true); is set to true on every new png added to the layer then lastly imagesavealpha($image,true); before save, you had it at the top. sometimes it will get reset – Nevis

Answer 2

This code worked for me:

$img=imagecreatetruecolor(180,20);
imagealphablending($img,false);

$col=imagecolorallocatealpha($img,255,255,255,127);
imagefilledrectangle($img,0,0,180,20,$col);
imagealphablending($img,true);

$font=$_SERVER["DOCUMENT_ROOT"].'/fonts/Arial.ttf';
$color = imagecolorallocate($img, 140, 173, 209);
imagettftext($img,11,0,5,14,$color,$font,'Text goes here'); 

header('Content-Type: image/png');
imagealphablending($img,false);
imagesavealpha($img,true);
imagepng($img);

Sperrylite

Answer 3

Try to replace
$col=imagecolorallocatealpha($image,255,255,255,127);
with
$col=imagecolorallocate($image,255,255,255);

and try to uncomment imagefilledrectangle line.
I can test this code - give me the pictures :)

Ibbie