PHP Watermarking - Zubrag

问题

I'm using zubrags PHP watermarking script (attached below) and it works great except when I try and use a PNG-24 as my watermark. The resulting image has a garbled, non-transparent watermark. I'm wondering if anyone could help explain what I would need to alter in the script below so that a PNG-24 embeds as a proper watermark on the image? I did come across this article: http://www.benholmen.com/blog/2008/12/adding-png-watermarks-to-jpegs-with-php/ which mentioned the use of PHP's imagealphablending() function for PNG-24 support.

Thanks in advance for any help. It's very appreciated :)

Zubrag's Watermark:

class Zubrag_watermark {

  var $offset_x = 0;
  var $offset_y = 0;
  var $quality = 100;
  var $image_type = -1; // Image type: 1 = GIF, 2 = JPG, 3 = PNG
  var $force_image_type = -1; // Change image type? (-1 = same as original, 1 = GIF, 2 = JPG, 3 = PNG)
  var $save_to_file = true;

  function Zubrag_watermark($image_path='', $offset_x=0, $offset_y=0) {
    $this->setImagePath($image_path);
    $this->setOffset($offset_x, $offset_y);
  }

  function setImagePath($image_path) {
    $this->image_path = $image_path;
  }

  function setOffset($x, $y) {
    $this->offset_x = $x;
    $this->offset_y = $y;
  }

  function ImageCreateFromType($type,$filename) {
   $im = null;
   switch ($type) {
     case 1:
       $im = ImageCreateFromGif($filename);
       break;
     case 2:
       $im = ImageCreateFromJpeg($filename);
       break;
     case 3:
       $im = ImageCreateFromPNG($filename);
       break;
    }
    return $im;
  }

  function ApplyWatermark($watermark_path) {

    $this->watermark_path = $watermark_path;

    // Determine image size and type
    $size = getimagesize($this->image_path);
    $size_x = $size[0];
    $size_y = $size[1];
    $image_type = $size[2]; // 1 = GIF, 2 = JPG, 3 = PNG

    // load source image
    $image = $this->ImageCreateFromType($image_type, $this->image_path);

    // Determine watermark size and type
    $wsize = getimagesize($watermark_path);
    $watermark_x = $wsize[0];
    $watermark_y = $wsize[1];
    $watermark_type = $wsize[2]; // 1 = GIF, 2 = JPG, 3 = PNG



    // load watermark
    $watermark = $this->ImageCreateFromType($watermark_type, $watermark_path);

    // where do we put watermark on the image?
    $dest_x = $size_x - $watermark_x - $this->offset_x;
    $dest_y = $size_y - $watermark_y - $this->offset_y;

    imagealphablending($image, true);
 imagecopymerge($image, $watermark, $dest_x, $dest_y, 0, 0, $watermark_x, $watermark_y, 100);  

    $this->image = &$image;
    $this->watermark = &$watermark;
    $this->image_type = $image_type;

  } // ApplyWatermark

  function OutputImageInternal($filename='') {

    $im = &$this->image;
    $res = null;

    $image_type = ($this->force_image_type != -1 ? $this->force_image_type : $this->image_type);

    // ImageGIF is not included into some GD2 releases, so it might not work
    // output png if gifs are not supported
    if(($image_type == 1)  && !function_exists('imagegif')) $image_type = 3;

    switch ($image_type) {
      case 1:
        if ($this->save_to_file) {
          $res = ImageGIF($im,$filename);
        }
        else {
          header("Content-type: image/gif");
          $res = ImageGIF($im);
        }
        break;
      case 2:
        if ($this->save_to_file) {
          $res = ImageJPEG($im,$filename,$this->quality);
        }
        else {
          header("Content-type: image/jpeg");
          $res = ImageJPEG($im, NULL, $this->quality);
        }
        break;
      case 3:
        if (PHP_VERSION >= '5.1.2') {
          // Convert to PNG quality.
          // PNG quality: 0 (best quality, bigger file) to 9 (worst quality, smaller file)
          $quality = 9 - min( round($this->quality / 10), 9 );
          if ($this->save_to_file) {
            $res = ImagePNG($im, $filename, $quality);
          }
          else {
            header("Content-type: image/png");
            $res = ImagePNG($im, NULL, $quality);
          }
        }
        else {
          if ($this->save_to_file) {
            $res = ImagePNG($im, $filename);
          }
          else {
            header("Content-type: image/png");
            $res = ImagePNG($im);
          }
        }
        break;
    }

    return $res;

  }

  function Output($type = -1) {
    $this->force_image_type = $type;
    $this->save_to_file = false;
    $this->OutputImageInternal();
  }

  function SaveAsFile($filename, $type = -1) {
    $this->force_image_type = $type;
    $this->save_to_file = true;
    $this->OutputImageInternal($filename);
  }

  function Free() {
    imagedestroy($this->image);
    imagedestroy($this->watermark);
  }

}

回答1:

Changing the function used in the code above from: imagecopymerged() to: imagecopy()

seemed to do the trick!

回答2:

The imagecopymerged() switch from to imagecopy() is definitely the answer. However, I still struggled with the above because that was ALL I changed! It took me a while to realize you have to remove the last value of the imagecopymerged() for it to work with imagecopy().

Here are some details as to the values required for each function:

int imagecopy ( resource dest_image, resource source_image, int dest_x, int dest_y, int source_x, int source_y, int source_width, int source_height)

int imagecopymerge ( resource dest_image, resource source_image, int dest_x, int dest_y, int source_x, int source_y, int source_width, int source_height, int merge_percentage)

来源：https://stackoverflow.com/questions/2452057/php-watermarking-zubrag