ThinkPHP watermark function repairs PNG transparent watermarks and increases JPEG image quality with adjustable quality, _PHP tutorial

/**
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* Add watermark to pictures
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* @static public
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* @param string $source original file name
* @param string $water watermark image
* @param string $$savename Image name after adding watermark
* @param string $alpha watermark transparency
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* @return string
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* @throws ThinkExecption
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*/
static public function water($source, $water, $savename=null, $alpha=80) {
//Check if the file exists
if (!file_exists($source) || !file_exists($water))
return false;

//Picture information
$sInfo = self::getImageInfo($source);
$wInfo = self::getImageInfo($water);

//If the image is smaller than the watermark image, no image will be generated
if ($sInfo["width"] < $wInfo["width"] || $sInfo['height'] < $wInfo['height'])
return false;

//Create image
$sCreateFun = "imagecreatefrom" . $sInfo['type'];
$sImage = $sCreateFun($source);
$wCreateFun = "imagecreatefrom" . $wInfo['type'];
$wImage = $wCreateFun($water);

//Set the color mixing mode of the image
imagealphablending($wImage, true);

//Image position, the default is the lower right corner right-aligned
$posY = $sInfo["height"] – $wInfo["height"];
$posX = $sInfo["width"] – $wInfo["width"];

/* In order to maintain the transparency of PNG, use imagecopy. Here is the modified one*/
imagecopy($sImage, $wImage, $posX, $posY, 0, 0, $wInfo['width'], $wInfo['height']);
//Generate mixed images, this is systematic
// imagecopymerge($sImage, $wImage, $posX, $posY, 0, 0, $wInfo['width'],$wInfo['height'], $alpha);
//Output image
$ImageFun = 'Image' . $sInfo['type'];
//If no save file name is given, the default is the original image name
if (!$savename) {
$savename = $source;
@unlink($source);
}
//Save the image. If it is jpg, set the watermark quality. Here is the modified one:
if ($sInfo['type'] == "jpg" || $sInfo['type'] == "jpeg") {
imagejpeg($sImage, $savename, 90);//The third parameter is the quality, because only imagejpeg supports this parameter
} else {
$ImageFun($sImage, $savename);
}
//$ImageFun($sImage, $savename);//This is system
imagedestroy($sImage);
}