Only resize images for themes which are being used instead of all installed themes.

Author: hostep

app/code/Magento/Catalog/Model/Product/Image/Cache.php

@@ -8,6 +8,7 @@
 use Magento\Catalog\Helper\Image as ImageHelper;
 use Magento\Catalog\Model\Product;
 use Magento\Theme\Model\ResourceModel\Theme\Collection as ThemeCollection;
+use Magento\Theme\Model\Config\Customization as ThemeCustomizationConfig;
 use Magento\Framework\App\Area;
 use Magento\Framework\View\ConfigInterface;
 
@@ -23,6 +24,11 @@ class Cache
      */
     protected $themeCollection;
 
+    /**
+     * @var ThemeCustomizationConfig
+     */
+    protected $themeCustomizationConfig;
+
     /**
      * @var ImageHelper
      */
@@ -41,10 +47,12 @@ class Cache
     public function __construct(
         ConfigInterface $viewConfig,
         ThemeCollection $themeCollection,
-        ImageHelper $imageHelper
+        ImageHelper $imageHelper,
+        ThemeCustomizationConfig $themeCustomizationConfig
     ) {
         $this->viewConfig = $viewConfig;
         $this->themeCollection = $themeCollection;
+        $this->themeCustomizationConfig = $themeCustomizationConfig;
         $this->imageHelper = $imageHelper;
     }
 
@@ -58,8 +66,10 @@ public function __construct(
     protected function getData()
     {
         if (!$this->data) {
+            $themes = $this->getThemesInUse();
+
             /** @var \Magento\Theme\Model\Theme $theme */
-            foreach ($this->themeCollection->loadRegisteredThemes() as $theme) {
+            foreach ($themes as $theme) {
                 $config = $this->viewConfig->getViewConfig([
                     'area' => Area::AREA_FRONTEND,
                     'themeModel' => $theme,
@@ -127,4 +137,20 @@ protected function processImageData(Product $product, array $imageData, $file)
 
         return $this;
     }
+
+    protected function getThemesInUse()
+    {
+        $themesInUse = [];
+
+        $registeredThemes = $this->themeCollection->loadRegisteredThemes();
+        $storesByThemes   = $this->themeCustomizationConfig->getStoresByThemes();
+
+        foreach ($registeredThemes as $registeredTheme) {
+            if (array_key_exists($registeredTheme->getThemeId(), $storesByThemes)) {
+                $themesInUse[] = $registeredTheme;
+            }
+        }
+
+        return $themesInUse;
+    }
 }

app/code/Magento/Catalog/Test/Unit/Model/Product/Image/CacheTest.php

@@ -43,6 +43,11 @@ class CacheTest extends \PHPUnit_Framework_TestCase
      */
     protected $themeCollection;
 
+    /**
+     * @var \Magento\Theme\Model\Config\Customization|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $themeCustomizationConfig;
+
     /**
      * @var \Magento\Catalog\Helper\Image|\PHPUnit_Framework_MockObject_MockObject
      */
@@ -70,6 +75,10 @@ protected function setUp()
             ->disableOriginalConstructor()
             ->getMock();
 
+        $this->themeCustomizationConfig = $this->getMockBuilder(\Magento\Theme\Model\Config\Customization::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
         $this->imageHelper = $this->getMockBuilder(\Magento\Catalog\Helper\Image::class)
             ->disableOriginalConstructor()
             ->getMock();
@@ -84,6 +93,7 @@ protected function setUp()
             [
                 'viewConfig' => $this->viewConfig,
                 'themeCollection' => $this->themeCollection,
+                'themeCustomizationConfig' => $this->themeCustomizationConfig,
                 'imageHelper' => $this->imageHelper,
             ]
         );
@@ -126,6 +136,12 @@ public function testGenerate()
             ->method('loadRegisteredThemes')
             ->willReturn([$themeMock]);
 
+        $this->themeCustomizationConfig->expects($this->once())
+            ->method('getStoresByThemes')
+            ->willReturn([
+                $themeMock->getThemeId() => [1]
+            ]);
+
         $this->viewConfig->expects($this->once())
             ->method('getViewConfig')
             ->with([