gd-PHP旋转PNG图片后图片变为无色，白色的样子

$source = imagecreatefrompng($fullFileName);
$rotate = imagerotate($source, 90, 0);
imagepng($rotate,$fullFileName,75);

三行代码，jpg的就没事，png的就变无色了

回复内容：

$source = imagecreatefrompng($fullFileName);
$rotate = imagerotate($source, 90, 0);
imagepng($rotate,$fullFileName,75);

三行代码，jpg的就没事，png的就变无色了