ImageMagick Watermark in PHP - How can I scale watermark with % of original image size instead of % of watermark image size?

Question

So I took ImageMagick Watermark in PHP code as available in www.rainbodesign.com and adjusted it so that it fits my needs: adding an overlay watermark image on the bottom right corner of the original image. This link triggers the conversion mywebsite.com/watermark.php?src=filepath-to-image and returns the new watermarked image. Here's the full code:

    <?php
// ImageMagick Watermark in PHP
// Copyright 2010-2011 by Richard L. Trethewey [email protected]
// http://www.rainbodesign.com/pub/watermark/
// 10/28/11 RLT
// If you use this script, I'd appreciate a link!  Thanks!

// 05/16/11 Updated to support text rotation, top/bottom/center
// 05/28/11 Updated to sanitize inputs
// 10/25/11 Added 'auto' color, inspired by Mikko's Blog http://valokuva.org/?p=59
//          RGB to HSL code by EasyRGB.com and http://serennu.com/colour/rgbtohsl.php

// 11/10/20 Deleted all references to text overlay and its settings
//          Added bottomright support

// Constants
$bContent = "Content-type: image/bmp";   // for BMP files
$jContent = "Content-type: image/jpeg";  // for JPEG files
$gContent = "Content-type: image/gif";   // for GIF files
$pContent = "Content-type: image/png";   // for PNG files
$tContent = "Content-type: image/tiff";  // for TIFF files
$old_image = '';    // Default base image filepath.

// User Settings and Defaults
$wm_image = 'images/watermark.png';     // Default watermark image file (include a path/URL, if necessary)
$wm_type = 'img';               // Set to 'msg' for text watermark.  Set to 'img' for image watermark.
$position = 'bottomright';   // Default watermark position - bottom left corner
$wm_opacity = 80;   // Default watermark image overlay opacity
$wm_rotate = 0;     // Default watermark image overlay rotation (in degrees)
// $gravity = 'SouthWest'; // Default watermark Imagemagick gravity - bottom left corner
$padding = 0;       // Default padding in pixels for watermark positioning.  Both top/bottom and left/right.

// Handle Query String option parameters
// src
 if (isset($_GET['src'])) { $old_image = $_GET['src']; }

// Block script hacking.
 $matches = array();
  if (preg_match('/([;\n\r])/i', $old_image, $matches)) { die; }

  switch(strtolower($position)) {
   case('bottom'):
    $gravity = 'SouthWest';
    break;
   case('bottomcenter'):
    $gravity = 'South';
    break;
   case('bottomright'):
      $gravity = 'SouthEast';
    break;
   case('top'):
    $gravity = 'NorthWest';
    break;
   case('topcenter'):
    $gravity = 'North';
    break;
   case('center'):
    $gravity = 'Center';
    break;
 } // end switch($position)

$dot = strrpos($old_image, '.');    // Set image type based on file name extension.  I know. Sorry, but it's fastest.
$extension = substr($old_image, $dot);
  switch($extension) {
   case('.jpg'):
   case('.jpeg'):
   $theContent = $jContent;
   $theWMType = 'jpg:-';
   break;
   case('.gif'):
   $theContent = $gContent;
   $theWMType = 'gif:-';
   break;
   case('.png'):
   $theContent = $pContent;
   $theWMType = 'png:-';
   break;
   case('.bmp'):
   $theContent = $bContent;
   $theWMType = 'bmp:-';
   break;
   case('.tif'):
   $theContent = $tContent;
   $theWMType = 'tif:-';
   break;
 } // end switch($extension)

// Image Overlay Watermark
 if ($wm_type == 'img') {
  $wmCmd = "convert $wm_image -background transparent -rotate $wm_rotate";
  $wmCmd .= " -scale 35%";
  $wmCmd .= " miff:- |";
  $wmCmd .= " composite -gravity $gravity -geometry +0+0 -blend " . $wm_opacity . "%";
  $wmCmd .= "  - $old_image $theWMType";
  } // endif $wm_type == 'img'

$test = 0; // set to 1 to view ImageMagick command being executed
 if ($test) {
 header('Content-type: text/plain');
 echo("$wmCmd\n");
 die;
}

  header($theContent);
  passthru($wmCmd);  // use passthru() to output binary data

exit;

?>

With this code I managed to add a watermark overlay image to the original images. But I need the watermak image to be 35% of original image size, not 35% of watermark image size! (Of course, with the watermark image mantaining it's aspect ratio)

// Image Overlay Watermark
 if ($wm_type == 'img') {
  $wmCmd = "convert $wm_image -background transparent -rotate $wm_rotate";
  $wmCmd .= " -scale 35%"; // here is where I need the magic to happen!
  $wmCmd .= " miff:- |";
  $wmCmd .= " composite -gravity $gravity -geometry +0+0 -blend " . $wm_opacity . "%";
  $wmCmd .= "  - $old_image $theWMType";
  } // endif $wm_type == 'img'

Does anybody know how to achieve this? Thanks in advance!! <3

Bonzo Bonzo · Accepted Answer · 2020-10-11T20:33:13

I would get the size of the original with getimagesize() ( I know that is a GD command ) and use the width from that to resize the watermark.

$size = getimagesize($old_image);
$watermakSize = $size[0]*.3; ( you can work out what 35% is )

$wmCmd .= " -resize {$watermakSize}x"; // here is where I need the magic to happen!

There are other ways but this is a simple one.

It is always good to mention what version of Imagemagick you are using.

ImageMagick Watermark in PHP - How can I scale watermark with % of original image size instead of % of watermark image size?

1 Answers