diff --git a/src/Canvas/CanvasInterface.php b/src/Canvas/CanvasInterface.php
index 9af8db9..57c86f3 100644
--- a/src/Canvas/CanvasInterface.php
+++ b/src/Canvas/CanvasInterface.php
@@ -2,9 +2,11 @@
 
 namespace StaticMapLite\Canvas;
 
+use Imagine\Image\ImageInterface;
+
 interface CanvasInterface
 {
-    public function getImage();
+    public function getImage(): ImageInterface;
     public function getWidth(): int;
     public function getHeight(): int;
     public function getCenterX(): float;
diff --git a/src/MapCache/MapCache.php b/src/MapCache/MapCache.php
index 87702b0..aa8cfd8 100644
--- a/src/MapCache/MapCache.php
+++ b/src/MapCache/MapCache.php
@@ -78,7 +78,8 @@ class MapCache
     public function cache(CanvasInterface $canvas): void
     {
         $this->mkdir_recursive(dirname($this->mapCacheIDToFilename()), 0777);
-        imagepng($canvas->getImage(), $this->mapCacheIDToFilename(), 9);
+
+        $canvas->getImage()->save($this->mapCacheIDToFilename());
 
         $output = new CacheOutput();
         $output->setFilename($this->mapCacheIDToFilename())