PHP implements the function of adding watermark to pictures_PHP tutorial

/**
* Add watermark to image (applicable to png/jpg/gif format)
*
* @author flynetcn
*
* @param $srcImg Original image
* @param $waterImg Watermark image
* @param $savepath Save path
* @param $savename Save name
* @param $positon Watermark position
* 1: Top left, 2: Top right, 3: Center , 4: Bottom left, 5: Bottom right
* @param $alpha transparency -- 0: completely transparent, 100: completely opaque
*
* @return success -- new after adding watermark Image address
* Failed - -1: The original file does not exist, -2: The watermark image does not exist, -3: The creation of the original file image object failed
* -4: The creation of the watermark file image object failed -5: The new image after watermarking failed to save
*/
function img_water_mark($srcImg, $waterImg, $savepath=null, $savename=null, $positon=5, $alpha=30)
{
$temp = pathinfo($srcImg);
$name = $temp['basename'];
$path = $temp['dirname'];
$exte = $temp['extension'];
$savename = $savename ? $savename : $ name;
$savepath = $savepath ? $savepath : $path;
$savefile = $savepath .'/'. $savename;
$srcinfo = @getimagesize($srcImg);
if (!$srcinfo) {
                                                                                                                                         -2; //The watermark image does not exist
}
$srcImgObj = image_create_from_ext($srcImg);
if (!$srcImgObj) {
return -3; //The creation of the original file image object failed
}
$waterImgObj = image_create_from_ext($waterImg);
if (!$waterImgObj) {
return -4; //Failed to create watermark file image object
}
switch ( $positon) {
//1 The top is on the left
case 1: $x=$y=0; break;
//2 The top is on the right
case 2: $x = $srcinfo[0 ]-$waterinfo[0]; $y = 0; break;
//3 centered
case 3: $x = ($srcinfo[0]-$waterinfo[0])/2; $y = ($srcinfo[1]-$waterinfo[1])/2; break;
//4 bottom left
case 4: $x = 0; $y = $srcinfo[1]-$waterinfo[1 ]; break;
//5 bottom right
case 5: $x = $srcinfo[0]-$waterinfo[0]; $y = $srcinfo[1]-$waterinfo[1]; break ;
default: $x=$y=0;
}
imagecopymerge($srcImgObj, $waterImgObj, $x, $y, 0, 0, $waterinfo[0], $waterinfo[1] , $alpha);
switch ($srcinfo[2]) {
case 1: imagegif($srcImgObj, $savefile); break;
case 2: imagejpeg($srcImgObj, $savefile); break ;
case 3: imagepng($srcImgObj, $savefile); break;
default: return -5; //Save failed
}
imagedestroy($srcImgObj);
imagedestroy($ waterImgObj);
return $savefile;
}


function image_create_from_ext($imgfile)
{ $info = getimagesize($imgfile);

$im = null;
switch ($info[2]) {
case 1: $im=imagecreatefromgif($imgfile); break;
case 2: $im=imagecreatefromjpeg($imgfile); break;
case 3: $im=imagecreatefrompng($imgfile); break;
}
return $im;
}