Restrict extractor options to a specific template

README.md

@@ -182,7 +182,7 @@ palette:
 
 #### 4.1. Select manually which image to extract colors from
 
-You can extract a color palette from an image file by activating the `extractor` option. It will override the manual options, if specified. Default is `false`.
+You can extract a color palette from a page's image file by activating the `extractor` option. It will override the manual options, if specified. Default is `false`.
 
 ```yaml
 palette:
@@ -191,6 +191,15 @@ palette:
   # no need for options anymore
 ```
 
+You can restrict the choices to a specific file template with the `template` option:
+
+```yaml
+palette:
+  type: color-palette
+  extractor: true
+  template: cover
+```
+
 #### 4.2. Automatically extract colors when an image matches a template
 
 Alternatively, you can make use of the `autotemplate` option (do not add the above `extractor` option in this case).

lib/api.php

@@ -7,8 +7,9 @@
 	        'method'  => 'GET',
             'action' => function () {
                 $uri      = get('uri');
+                $template = get('template');
 	            $page     = kirby()->page($uri);
-	            $files    = $page->images();
+	            $files    = $template !== 'undefined' ? $page->images()->template($template) : $page->images();
                 $data     = [];
 
                 $thumb = array(

lib/fields.php

@@ -29,6 +29,9 @@
             	$yaml = Yaml::decode($value);
                 return count($yaml) ? $yaml : $value;
             },
+            'template' > function($template = null) {
+            	return $template;
+            },
             'autotemplate' > function($autotemplate = null) {
             	return $autotemplate;
             }

src/components/field/ColorPalette.vue

@@ -47,6 +47,7 @@ export default {
         uri: String,
         endpoints: Object,
         autotemplate: String,
+        template: String,
 
         // general options
         label: String,
@@ -167,7 +168,7 @@ export default {
             return true;
         },
         openSelector() {
-            this.$api.get('color-palette/get-files', {uri: this.uri})
+            this.$api.get('color-palette/get-files', {uri: this.uri, template: this.template})
                 .then(files => {
                     this.$refs.selector.open(files, {
                         max: false,