php 给图片添加水印 实例

方法已经放在下面了：

/**
 * 添加图片水印
 *
 * @param $picPath
 * @param $logoPath
 */
private function _addWaterMark($picPath, $logoPath)
{
    //如果图片不存在或者logo不存在则不处理
    if (!file_exists($picPath) || !file_exists($logoPath)) {
        return;
    }

    //创建图片的实例
    $im = imagecreatefromstring(file_get_contents($picPath));

    //获取水印源
    $watermark = imagecreatefromstring(file_get_contents($logoPath));

    //获取图、水印 宽高类型
    list($bgWidth, $bgHight, $bgType) = getimagesize($picPath);
    list($logoWidth, $logoHight, $logoType) = getimagesize($logoPath);

    //定义平铺数据
    $xLength = $bgWidth - 10; //x轴总长度
    $yLength = $bgHight - 10; //y轴总长度

    //创建透明画布 伪白色
    $opacity = 15;
    $w       = imagesx($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 < $xLength; $x++) {
        for ($y = 0; $y < $yLength; $y++) {
            imagecopymerge($im, $cut, $x, $y, 0, 0, $logoWidth, $logoHight, $opacity);
            $y += $logoHight;
        }
        $x += $logoWidth;
    }
    imagejpeg($im, $picPath);
    imagedestroy($im);
}

效果如下：