php图片加水印原理(超简单的实例代码)

文字水印:
代码如下:

$w = 80; 
$h = 20; 
$im = imagecreatetruecolor($w,$h); 
$textcolor = imagecolorallocate($im, 123, 12, 255); 
$white = imagecolorallocate($im, 255, 255, 255); 
$grey = imagecolorallocate($im, 128, 128, 128); 
$black = imagecolorallocate($im, 0, 0, 0); 
imagefilledrectangle($im, 0, 0, 399, 29, $grey); //画一矩形并填充 

// 把字符串写在图像左上角 
imagestring($im, 3, 2, 3, "Hello world!", $textcolor); 

// 

输出图像
header("Content-type: image/jpeg");
imagejpeg($im);
imagedestroy($im);

图片水印

$groundImg = "DSC05940.jpeg";
$groundInfo = getimagesize($groundImg);
$ground_w = $groundInfo[0];
//print_r($groundInfo);
$ground_h = $groundInfo[1];
switch($groundInfo[2]){
case 1:
$ground_im = imagecreatefromgif($groundImg);
break;
case 2:
$ground_im = imagecreatefromjpeg($groundImg);
break;
case 3:
$ground_im = imagecreatefrompng($groundImg);
break;
}

$waterImg = "DSC05949.jpeg";
$imgInfo =getimagesize($waterImg);
$water_w = $imgInfo[0];
$water_w = $imgInfo[1];

switch($imgInfo[2]){
case 1:
$water_im = imagecreatefromgif($waterImg);
break;
case 2:
$water_im = imagecreatefromjpeg($waterImg);
break;
case 3:
$water_im = imagecreatefrompng($waterImg);
break;
}
imagecopy($ground_im,$water_im,100,100,0,0,500,500);
header("Content-type: image/jpeg");

imagejpeg($ground_im);

合并图片php提供了很多函数：例如：imagecopymerge，imagecopyresized