How to Improve my php image resizer to support alpha png and transparent GIFs
- by David
Hi,
I use this function to resize images but i end up with ugly creepy image with a black background if it's a transparent GIF or PNG with alpha, however it works perfectly for jpg and normal png.
function cropImage($nw, $nh, $source, $stype, $dest) {
$size = getimagesize($source);
$w = $size[0];
$h = $size[1];
switch($stype) {
case 'gif':
$simg = imagecreatefromgif($source);
break;
case 'jpg':
$simg = imagecreatefromjpeg($source);
break;
case 'png':
$simg = imagecreatefrompng($source);
break;
}
$dimg = imagecreatetruecolor($nw, $nh);
switch ($stype)
{
case "png":
imagealphablending( $dimg, false );
imagesavealpha( $dimg, true );
$transparent = imagecolorallocatealpha($dimg, 255, 255, 255, 127);
imagefilledrectangle($dimg, 0, 0, $nw, $nh, $transparent);
break;
case "gif":
// integer representation of the color black (rgb: 0,0,0)
$background = imagecolorallocate($simg, 0, 0, 0);
// removing the black from the placeholder
imagecolortransparent($simg, $background);
break;
}
$wm = $w/$nw;
$hm = $h/$nh;
$h_height = $nh/2;
$w_height = $nw/2;
if($w> $h) {
$adjusted_width = $w / $hm;
$half_width = $adjusted_width / 2;
$int_width = $half_width - $w_height;
imagecopyresampled($dimg,$simg,-$int_width,0,0,0,$adjusted_width,$nh,$w,$h);
} elseif(($w <$h) || ($w == $h)) {
$adjusted_height = $h / $wm;
$half_height = $adjusted_height / 2;
$int_height = $half_height - $h_height;
imagecopyresampled($dimg,$simg,0,-$int_height,0,0,$nw,$adjusted_height,$w,$h);
} else {
imagecopyresampled($dimg,$simg,0,0,0,0,$nw,$nh,$w,$h);
}
imagejpeg($dimg,$dest,100);
}
Example : cropImage("300","200","original.png","png","new.png");
I use php 5.3.2 and the GD library bundled (2.0.34 compatible)
How to make it support transparency? i've added imagealphablending() and imagesavealpha but it didn't work. Or atlast is there any similar good classes?
Thanks
