I have a PHP script that resizes .jpg, .gif, and .png files to a bounding box.
$max_width = 500;
$max_height = 600;
$filetype = $_FILES["file"]["type"];
$source_pic = "img/" . $idnum;
if($filetype == "image/jpeg")
{
$src = imagecreatefromjpeg($source_pic);
} else if($filetype == "image/png")
{
$src = imagecreatefrompng($source_pic);
} else if($filetype == "image/gif")
{
$src = imagecreatefromgif($source_pic);
}
list($width,$height)=getimagesize($source_pic);
$x_ratio = $max_width / $width;
$y_ratio = $max_height / $height;
if( ($width <= $max_width) && ($height <= $max_height) )
{
$tn_width = $width;
$tn_height = $height;
} else if (($x_ratio * $height) < $max_height)
{
$tn_height = ceil($x_ratio * $height);
$tn_width = $max_width;
} else {
$tn_width = ceil($y_ratio * $width);
$tn_height = $max_height;
}
$tmp = imagecreatetruecolor($tn_width,$tn_height);
imagecopyresampled($tmp,$src,0,0,0,0,$tn_width, $tn_height,$width,$height);
$destination_pic = "img/thumbs/" . $idnum . "thumb";
if($filetype == "image/jpeg")
{
imagejpeg($tmp,$destination_pic,80);
} else if($filetype == "image/png")
{
imagepng($tmp,$destination_pic,80);
} else if($filetype == "image/gif")
{
imagegif($tmp,$destination_pic,80);
}
imagedestroy($src);
imagedestroy($tmp);
The script works fine with jpeg and gif but when running on a png the file will be corrupted.
Is there anything special I need to use when working with a png? I have never worked with this sort of thing in PHP so I'm not very familiar with it.
First, check if PNG support is enabled in your gd lib. You can get this from phpinfo, as function phpinfo().
You cannot set the param $quality of imagepng() to 80, only 1 to 9 is possible. It's better to remove it.
imagepng($tmp, $destination_pic);
And if you have some problems with transparency, have a look at following functions:
imagealphablending();
imagesavealpha();