diff --git a/imagemagick.api.php b/imagemagick.api.php
index b05fafe..12cd907 100644
--- a/imagemagick.api.php
+++ b/imagemagick.api.php
@@ -2,6 +2,68 @@
 
 /**
  * @file
- * API documentation for ImageMagick module.
+ * API documentation for the ImageMagick module.
  */
 
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Alter an image as it is loaded by the ImageMagick toolkit.
+ *
+ * @param $image
+ *   An image object.
+ *
+ * @see image_load()
+ * @see image_imagemagick_load()
+ */
+function hook_imagemagick_load_alter(stdClass $image) {
+}
+
+/**
+ * Alter an image before it is saved by the ImageMagick toolkit.
+ *
+ * @param $image
+ *   An image object.
+ * @param $context
+ *   An associative array of information about the image being saved:
+ *   - destination: The file URI where $image will be saved to.
+ *
+ * @see image_save()
+ * @see image_imagemagick_save()
+ */
+function hook_imagemagick_save_alter(stdClass $image, $context = array()) {
+}
+
+/**
+ * Alter the arguments to the ImageMagick 'convert' command-line program.
+ *
+ * @param $args
+ *   An array of arguments to the ImageMagick 'convert' command-line program.
+ * @param $context
+ *   An associative array of information about the image being altered:
+ *   - source: The filesystem path of the original image.
+ *   - source_original: The original file URI of the image.
+ *   - destination: The filesystem path for the derivative image.
+ *   - destination_original: The original file URI for the derivative image.
+ *   - destination_format: The target image format for the derivative image.
+ *     Defaults to an empty string.
+ *
+ * ImageMagick automatically converts the target image to the format denoted by
+ * the file extension. However, since changing the file extension is not always
+ * an option (e.g., for derivative images of core Image module styles), you can
+ * specify an alternative derivative image format in
+ * $context['destination_format']. 'destination_format' is a string denoting a
+ * file extension. If not empty, it is passed to ImageMagick's convert binary in
+ * the syntax "[destination_format]:[destination]".
+ *
+ * @see http://www.imagemagick.org/script/command-line-processing.php#output
+ * @see http://www.imagemagick.org/Usage/files/#save
+ *
+ * @see _imagemagick_convert()
+ */
+function hook_imagemagick_arguments_alter($args, $context = array()) {
+}
+
diff --git a/imagemagick.module b/imagemagick.module
index c42f3b4..d9b6c4c 100644
--- a/imagemagick.module
+++ b/imagemagick.module
@@ -359,28 +359,47 @@ function image_imagemagick_get_info(stdClass $image) {
 /**
  * Calls the convert executable with the specified filter.
  */
-function _imagemagick_convert($source, $dest, $args) {
+function _imagemagick_convert($source, $destination, $args) {
+  // Backup original paths for alter hook context.
+  $source_original = $source;
+  $destination_original = $destination;
+
   $source = drupal_realpath($source);
-  $dest = drupal_realpath($dest);
+  $destination = drupal_realpath($destination);
+  $destination_format = '';
 
   $args['quality'] = '-quality ' . escapeshellarg(variable_get('imagemagick_quality', 75));
 
   // Allow other modules to alter the ImageMagick command line parameters.
   $context = array(
-    'source' => $source,
-    'destination' => $dest,
+    'source' => &$source,
+    'source_original' => $source_original,
+    'destination' => &$destination,
+    'destination_original' => $destination_original,
+    'destination_format' => &$destination_format,
   );
   drupal_alter('imagemagick_arguments', $args, $context);
 
+  // If the format of the derivative image was changed, concatenate the new
+  // image format and the destination path, delimited by a colon.
+  // @see http://www.imagemagick.org/script/command-line-processing.php#output
+  // @see hook_imagemagick_arguments_alter()
+  if ($destination_format !== '') {
+    $destination_format .= ':' . $destination;
+  }
+  else {
+    $destination_format = $destination;
+  }
+
   // To make use of ImageMagick 6's parenthetical command grouping we need to make
   // the $source image the first parameter and $dest the last.
   // @see http://www.imagemagick.org/Usage/basics/#cmdline
-  $command = escapeshellarg($source) . ' ' . implode(' ', $args) . ' ' . escapeshellarg($dest);
+  $command = escapeshellarg($source) . ' ' . implode(' ', $args) . ' ' . escapeshellarg($destination_format);
 
   if (_imagemagick_convert_exec($command, $output, $error) !== TRUE) {
     return FALSE;
   }
-  return file_exists($dest);
+  return file_exists($destination);
 }
 
 /**