Drupal 7 Module Development

Chapter 11
After this setup, we start getting into the meat of the function.
$local_path = file_unmanaged_save_data($twitpic_image, $local_uri,
FILE_EXISTS_REPLACE);
$local_image = image_load($local_path);
Since we are not associating this file with any other content within Drupal,
we have no need for it to be entered into the files table. Therefore, we use
file_unmanaged_save_data() as opposed to file_save_data(), in order
to prevent unnecessary records from being written.
Once the file is saved, we call image_load() to get back $local_image, a Drupal
image object that we can pass on to the image manipulation functions. Like the file
object, an image object contains a variety of information about the image that has
been loaded, including its height and width, mime-type, and a handle to the image.
Now that we have an image object, we can mess with it using Drupal's API
functions. For the purposes of this experiment, we just hardcode some sample
manipulations in, to see the kind of things you can do.
switch ($operation) {
case 'desaturate':
image_desaturate($local_image);
break;
case 'scale':
image_scale($local_image, NULL, 50, FALSE);
break;
}
case 'rotate':
image_rotate($local_image, 45, 0x7D26CD);
break;
As you can see, we have three possible manipulations depending on the operation
passed in through the URL. All of these functions work directly on our image
object, $local_image which is passed by reference, so we don't need to worry
about return values.
The first example, image_desaturate(), is the simplest. It just converts the image
to grayscale, with no configuration arguments.
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