Imagemagick port to Drupal 8

Here's a patch against the current 7.x-1.x branch that would generate a possible 8.x-1.x branch. It's based on the work in the sandbox mentioned in the IS. There is review and more testing to do but locally this is working pretty much ok. I do not expect major changes to the image system API at this point of core development, so I thought it can be time to post here the current status of the sandbox.

A few points from the sandbox work:

1. the former 'ops' array of command line arguments has been renamed and made protected in the toolkit. Toolkit methods have been introduced to manage the arguments.
2. 'imagemagick_advanced' module is merged into 'imagemagick'
3. implements automated tests based on GDToolkitTest - not sure they qualify for the automated testing infrastructure, but they work locally provided the convert executable can be accessed without need to specify a full path
4. implements #2064223: image_imagemagick_get_info() should use Imagemagick Identify command
5. implements #1551262: Rotate should alter dimensions
6. in the rotate operation, a +repage operation is added, otherwise further operations like e.g. crop would not work properly because of changed image geometry
7. following comments in #1967630: Images with non-ASCII characters in their filenames cannot be converted., #2112987: cannot convert images with UTF-8 filenames, #1502924: escapeshellarg() has problems with non-ASCII filenames, #352262: Non-ascii problems with imagemagick toolkit, and given that escapeshellarg() drops non-ascii characters (for filenames, but also if you want to use 'label:' Imagemagick commands), I replaced calls to escapeshellarg() with a method that just encapsulates strings between quotes. Something better could be done but for the time being it works.

Re. #2 I am fine to get commit access but can not promise to be able to maintain it ongoing, thanks.

Couple of additions to #3:

1. Following up on #3.7, implemented the solution proposed in #1502924: escapeshellarg() has problems with non-ASCII filenames.
2. Using the identify command to parse image file (see #3.4), it is possible to retrieve the EXIF orientation tag from JPEG images, and manage it so that the auto-orientation image operation can track the image dimensions before applying further operations. So practically #1964064: auto-orient needs to (conditionally) change dimensions is implemented here.

Thanks @Berdir, not really sure I grasp what you mean. I confirm I am also seeing the toolkit only after refreshing all caches after a module install. Is it a problem with the core image toolkits plugin manager? If so, would you mind creating a core issue for that - I would need more details before I can say if I can work on that.

Never mind, I think I understood. Created #2467775: Contrib toolkits are not picked up after module install in Drupal core issue queue.

Refreshed patch to take care of a few things that changed in core since #4 in Dec 2014 (immutable configuration, String class dropped).

Can anybody review core's #2311679: Separate MIME type mapping from ExtensionMimeTypeGuesser?

That would help to get rid of the workaround to get the image mimetype from the source format through a dummy filename

+++ b/src/Plugin/ImageToolkit/ImagemagickToolkit.php
@@ -0,0 +1,915 @@
+  /**
+   * {@inheritdoc}
+   */
+  public function getMimeType() {
+    // @todo change if extension mapping service gets in, see #2311679
+    $format = $this->getSourceFormat();
+    return empty($format) ? NULL : $this->mimeTypeGuesser->guess('dummy.' . $format);
+  }
+
+  /**

Aligned to current sandbox:

• made Rectangle class equal to the one in #1551686-23: Image rotate dimensions callback can calculate new dimensions for every angle
• changed ::transformDimensions methods of image effects provided by ImageMagick (see #2420751: ImageEffectBase::transformDimensions() should have a sane default implementation)
• changed to use 'file.mime_type.guesser.extension' instead of 'file.mime_type.guesser' for mimetype guessing, interim waiting for #2311679: Separate MIME type mapping from ExtensionMimeTypeGuesser

#8: +1

Updated after core's #1364670: ImageStyle::transformDimensions unable to deal with all effects., now AutoOrientImageEffect::transformDimensions() can use the original image EXIF data to determine styled image dimensions.

Can a maintainer open a 8.x-1.x dev branch?

I got co-maintainership of this module and made a first commit, however different from the patch in #12. Will create a new plan issue to move forward.