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Resizing Images with PHP and Mogrify - Page 2

by: John Masterson
|
August 19, 2002

Mogrify to the Rescue
Mogrify is one of the programs included in the extremely powerful ImageMagick graphics manipulation suite. It is capable of changing colors, sizes, formats, and effects of an image in any of dozens of common formats. It was the perfect tool for this job.
The first step, after actually uploading the original image to the server, is to determine its current dimensions:
<xmp>
  $currentimagesize = getimagesize($UPLOADS_URL . $imagename);
</xmp>
This returns an array of information about the image. In this case, we're interested in the height and width. $UPLOADS_URL is a global variable we set which simply points at the location of the uploaded original image.
<xmp>
  $image_width = $currentimagesize[0];
  $image_height= $currentimagesize[1];
</xmp>
To resize the image, while retaining its original proportions, we need to determine the current dimensions and then calculate the new desired size (based on our maximum acceptable size of 200 pixels by 200 pixels).

<?php
  
if (($image_height &gt$max) || ($image_width &gt$max)) 
  {   
    if (
$image_height &gt$image_width
    { 
      
$sizefactor = (double) ($max $image_height);
    } 
    else 
    {
      
$sizefactor = (double) ($max $image_width) ;
    }
  }    

  
$newwidth = (int) ($image_width $sizefactor);
  
$newheight = (int) ($image_height $sizefactor); 
?>
In other words, if our uploaded image is 800 pixels wide by 200 pixels tall, the $sizefactor is 0.25 (200/800), and both dimensions are multiplied by this number to get a new image size of 200 pixels wide by 50 pixels high. The only thing left to do is the resizing itself:

<?php
  $newsize 
$newwidth "x" $newheight;

  
$cmd "/usr/X11R6/bin/mogrify -resize $newsize ".
         
"$UPLOAD_PATH/$newname 2&gt;&amp;1";     

  
exec($cmd$exec_output$exec_retval);

  if(
$exec_retval &gt0)
  {
    print 
"ERROR: exec() error: $exec_output[0]";
  }
  else
  {
    print 
"Image was resized from " $image_width "x" .
          
$image_height " to $newsize :)";
  }
?>
Note that that path to mogrify on your server will probably be different than the one on the Modwest.com server (/usr/X11R6/bin/mogrify). Also note that we redirect STDERR to STDOUT (2>&1) in the exec() line. This assures that we catch any error or warning message generated during the resizing process.
Having resized the image, all that remains is to insert it into a database or move it to the appropriate location.
Disaster Averted
Thanks to ImageMagick's mogrify program, a little bit of PHP code has prevented our client from slapping a huge image on the front page of their site, while requiring no technical graphic manipulation or other additional work on the part of their non-technical staff.

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