A small example of adding watermark to php images

/**
 * 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 $alpha Transparency- - 0: Completely transparent, 100: Completely opaque
 *
 * @return Success -- the new image address after adding watermark
 * Failure -- -1: The original file does not exist, -2: The watermarked image does not exist, -3: The original file image object failed to be created
 * -4: The watermark file image object failed to be created -5: The new image after watermarking failed to be saved
 * @Editor: bbs.it-home.org
*/
function img_water_mark($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) {
 return -1; //The original file does not exist
 }
 $waterinfo = @getimagesize($waterImg);
 if (!$waterinfo) {
 return -2; //The watermark image does not exist
 }
 $srcImgObj = image_create_from_ext($srcImg);
 if (!$srcImgObj) {
 return -3; //Failed to create the original file image object
 }
 $waterImgObj = image_create_from_ext($waterImg);
 if (!$waterImgObj) {
 return -4; //Creation of watermark file image object failed
 }
 switch ($positon) {
 //1 top to the left
 case 1: $x=$y=0; break;
 //2 top to the right
 case 2: $x = $srcinfo[0]-$waterinfo[0]; $y = 0; break;
 //3 is centered
 case 3: $x = ($srcinfo[0]-$waterinfo[0] )/2; $y = ($srcinfo[1]-$waterinfo[1])/2; break;
 //4 bottom is on the left
 case 4: $x = 0; $y = $srcinfo[1]-$ waterinfo[1]; break;
 //5 bottom is on the 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;
}