使用 PHP 实现 PNG 透明度

嘿，当我从 png 创建缩略图时，试图保持 png 的透明度时遇到了一些麻烦，有人有这方面的经验吗？任何帮助都会很棒，这就是我目前正在做的事情：

$fileName= "../js/ajaxupload/tees/".$fileName;

list($width, $height) = getimagesize($fileName);

$newwidth = 257;
$newheight = 197;

$thumb = imagecreatetruecolor($newwidth, $newheight);
imagealphablending($thumb, true);
$source = imagecreatefrompng($fileName);
imagealphablending($source, true);

imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

imagesavealpha($thumb, true);
imagepng($thumb,$newFilename);

我过去曾成功地这样做过：

$thumb = imagecreatetruecolor($newwidth, $newheight);
imagealphablending($thumb, false);
imagesavealpha($thumb, true);  

$source = imagecreatefrompng($fileName);
imagealphablending($source, true);

imagecopyresampled($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

imagepng($thumb,$newFilename);

我发现使用输出图像质量要好得多imagecopyresampled() than imagecopyresized()