使用php给图片添加全屏水印

转载自：http://blog.he29.com/wblog/?p=1045

经常会看到有些比如身份证照片等等为了防止被盗用, 经常会加上全屏水印,今天我是为了给一份合同添加水印

$bigImgPath = "bgt.jpg"; //原图
$logo = "logo.png"; //水印
$im = imagecreatefromstring(file_get_contents($bigImgPath));
//获取水印源
$watermark = imagecreatefromstring(file_get_contents($logo));
//获取图、水印 宽高类型
list($bgWidth, $bgHight, $bgType) = getimagesize($bigImgPath);
list($logoWidth, $logoHight, $logoType) = getimagesize($logo);
//定义平铺数据
$x_length = $bgWidth - 10; //x轴总长度
$y_length = $bgHight - 10; //y轴总长度
//创建透明画布 伪白色
$opacity=20;
$w = imagesx($watermark);
$h = imagesy($watermark);
$cut = imagecreatetruecolor($w,$h);
$white = imagecolorallocatealpha($cut, 255,255,255,0);
imagefill( $cut, 0, 0, $white );
//整合水印
imagecopy($cut, $watermark, 0, 0, 0, 0, $w, $h);
//循环平铺水印
for ($x = 0; $x < $x_length; $x++)
{
    for ($y = 0; $y < $y_length; $y++) {
        imagecopymerge($im, $cut, $x, $y, 0, 0, $logoWidth, $logoHight, $opacity);
        $y += $logoHight;
    }
    $x += $logoWidth;
}
//header("Content-type:image/png");
// imagejpeg 的第二个参数不传, 默认是显示图片
imagejpeg($im,'hhh.jpg');

生成的效果如下: