这是我在watermark.php 文件：

<?php
// loads a png, jpeg or gif image from the given file name
function imagecreatefromfile($image_path) {
// retrieve the type of the provided image file
list($width, $height, $image_type) = getimagesize($image_path);

// select the appropriate imagecreatefrom* function based on the determined
// image type
switch ($image_type)
 {
  case IMAGETYPE_GIF: return imagecreatefromgif($image_path); break;
  case IMAGETYPE_JPEG: return imagecreatefromjpeg($image_path); break;
  case IMAGETYPE_PNG: return imagecreatefrompng($image_path); break;
  default: return \'\'; break;
 }
}

// load source image to memory
$image = imagecreatefromfile($_GET[\'image\']);
if (!$image) die(\'Unable to open image\');

// load watermark to memory
$watermark = imagecreatefromfile($_GET[\'watermark\']);
if (!$image) die(\'Unable to open watermark\');

// calculate the position of the watermark in the output image (the
// watermark shall be placed in the lower right corner)
 $watermark_pos_x = imagesx($image) - imagesx($watermark) - 8;
$watermark_pos_y = imagesy($image) - imagesy($watermark) - 10;

// merge the source image and the watermark
  imagecopy($image, $watermark,  $watermark_pos_x, $watermark_pos_y, 0, 0,
  imagesx($watermark), imagesy($watermark));

// output watermarked image to browser
header(\'Content-Type: image/jpeg\');
imagejpeg($image, \'\', 100);  // use best image quality (100)

// remove the images from memory
imagedestroy($image);
imagedestroy($watermark);

然后变成.htaccess 文件：

RewriteEngine on
RewriteCond %{REQUEST_URI} (800x...|...x800)\\.(png|jpe?g|gif)
RewriteRule ^([^tn].*\\.(gif|jpg|png))$ /wp-content/uploads/watermark.php?image=$1&watermark=watermark.png [NC]

这里是。htaccess获取名称中包含800x或x800的jpg、png或gif请求（仅在大图像上应用水印），将其重定向到watermark.php 在图像上添加水印的脚本。

这是一个初学者，您应该通过定义要在中应用的规则来适应您的需要.htaccess文件对于我们的案例，我们在媒体选项中定义了800x800大小。