Fill the Alt Text of the Image File using Google Vision API

I think that approach of the label detection is better for alt attribute. Because not all the images have landmarks, but I think that all images have the label.
Using of the Landmark detection can be useful, but I don't think that makes sense to fill alt by landmark by default.
Can we have the feature to fill alt by landmark but make it configurable?

What do you think about it?

Taxonomy terms as tags and filling the alt attribute are two different features. Please do not confuse it.
For me as an end user would be nice to be able enable checkbox "Fill alt/title by Google Vision API" and select method: Label Detection or Landmark or etc...

1. +++ b/google_vision.module
   @@ -159,3 +191,66 @@ function google_vision_file_entity_add_labels($file, $field, $vid) {
   +          // If we have retrieved labels.
   

   if there will be no response then $output would never set.

2. +++ b/google_vision.module
   @@ -159,3 +191,66 @@ function google_vision_file_entity_add_labels($file, $field, $vid) {
   +    $entity->set('field_image_alt_text', $output);
   

   Add a check if $output is available then set the value. See the review above in case 'labels'

Rest looks good to me.We need test coverage for this as well.

Could you explain what is "field_image_alt_text" and why is it hardcoded?

Committed.

I have several remarks:
1. Please check my additional commit. If you don't agree with something, please let me know.
2. Why do you use name "features" for this functionality? This name looks pretty abstract.
3. If the user will select any option for "features" he will be not able to disable it. Please add the option "none".
4. I think that better to fill "alt" field only if it's empty. Better to give the user ability to overwrite the alt for certain image manually.

#2- I had derived the name "features" from the functionality of the Cloud Vision API.

I propose to change it. Features is too abstract name. What about "alt_auto_filling" or something like this?

#4- The alt field is filled as soon as the file is uploaded. At that moment, the field remains always empty. However, the user may override the value if he feels.

No in "google_vision_entity_presave" you always override alt on value from Google Vision. There is no way to set custom alt.

I propose to change it. Features is too abstract name. What about "alt_auto_filling" or something like this?

+1 to this.

+++ b/google_vision.module
@@ -241,14 +250,25 @@ function google_vision_set_alt_text($entity, $field) {
+        case 'none':
+          // If none is selected, do nothing.
+          break;

Why this case ?
can't we use the default value if there's not any case ?

+++ b/google_vision.module
@@ -241,14 +250,25 @@ function google_vision_set_alt_text($entity, $field) {
+ * Edit the current value of the Alt Text field of the image file.

Add a @TODO here to move this to the service later if there will be more helper functions like this.

Rest looks good to go.Thanks!

Ignore the #23 patch and interdiff.
i have filed a followup issue for it https://www.drupal.org/node/2776441

Still RTBC for #19
Assigning to eugene for final look into this.

Patch in #19 no longer applies to head. Please reoll it.

+++ b/google_vision.module
@@ -353,7 +366,15 @@ function google_vision_set_alt_text($entity, $field) {
+
+/**
+ * Edit the current value of the Alt Text field of the image file.
+ */
+function google_vision_edit_alt_text($entity, $field, $value) {
+  //Set the new value to the Alt Text field.
+  $entity->set($field->getName(), $value);
+}

Add a followup to move this function to a helper service.

Committed and pushed to 8.x-1.x
Thanks!