ImageMagick for thumbnails

I love WordPress RC3. It is just wonderful. New support for uploading pictures right where you post stuff is plain awesome.

I had one problem, though – my host does not have PHP compiled with GD, so thumbnail generation were not working for me. At the same time, I have shell access, and it was really easy for me to download ImageMagick command line utility – which I did. I’m sure some users might be in the same situation, so I’ll share my findings.

Maybe the developers of WordPress will even consider including support for ImageMagick in the final release – since it should be very easy (took me only 1 hour).

But first – why use ImageMagick?
1) ImageMagick does not have to be compiled with PHP – very easy option when you don’t have GD.
2) ImageMagick is faster than GD and generates better quality thumbnails. It’s the library of choice for many gallery projects.

How do I get ImageMagick to work on my site?
a) Download ImageMagick package from https://www.imagemagick.org/script/download.php
b) Untar, put in a directory where the web server can execute the binaries.
c) Make minor (almost tiny!) changes to wp-admin/admin-functions.php:

1) Find the function wp_create_thumbnail(). Add the following as its first line:
return alex_hack_thumbnail_using_imagemagick($file, $max_side, $filter);

2) Copy the following function above wp_create_thumbnail():

function alex_hack_thumbnail_using_imagemagick($file, $max_side, $filter = '') {
// FIX THIS TO POINT TO YOUR IMAGEMAGICK INSTALLATION!!!
// Make sure that the web server can execute scripts from this directory.
$PATH_TO_CONVERT = "/home/alex94040/imagemagick/bin/";

if (file_exists($file)) {
$image_attr = getimagesize($file);

$image_attr = getimagesize($file);

// figure out the longest side

if ($image_attr[0] > $image_attr[1]) {
$image_width = $image_attr[0];
$image_height = $image_attr[1];
$image_new_width = $max_side;

$image_ratio = $image_width / $image_new_width;
$image_new_height = $image_height / $image_ratio;
//width is > height
} else {
$image_width = $image_attr[0];
$image_height = $image_attr[1];
$image_new_height = $max_side;

$image_ratio = $image_height / $image_new_height;
$image_new_width = $image_width / $image_ratio;
//height > width
}

// If no filters change the filename, we'll do a default transformation.
if ( basename($file) == $thumb = apply_filters('thumbnail_filename', basename($file)) )
$thumb = preg_replace('!(\.[^.]+)?$!', __('.thumbnail').'$1', basename($file), 1);

$thumbpath = str_replace(basename($file), $thumb, $file);

$convert_str = $PATH_TO_CONVERT.'convert'.
' -sample '.$image_new_width.'x'.$image_new_height. // new size
' "'.$file.'"'. // source file to convert
' "'.$thumbpath.'"'; // destination file = thumbnail
exec($convert_str, $array_output, $return_value); // call ImageMagick command line utility to do the conversion
if($return_value != 0) {
$error = __('Error while creating image '.$file.'! <br>Return Value: '.$return_value.', output:<br>');
$error .= __("<br>Command: ".$convert_str.'<br>');
}
} else {
$error = __('File not found');
}

if (!empty ($error)) {
return $error;
} else {
return $thumbpath;
}
}

3) Correct the path to the imagemagick installation in the $PATH_TO_CONVERT variable in the code that you just pasted.

Good luck!!