Fix bug when loading png greyscale type

turn image into rgb if colorspace if other than CMYK, RGB, HSL or HSV.
this prevents working on greyscale colorspace images when loading from
PNG color type greyscale format.

src/Drivers/Imagick/Decoders/NativeObjectDecoder.php

@@ -17,6 +17,13 @@
 
 class NativeObjectDecoder extends SpecializableDecoder implements SpecializedInterface
 {
+    protected const SUPPORTED_COLORSPACES = [
+        Imagick::COLORSPACE_SRGB,
+        Imagick::COLORSPACE_CMYK,
+        Imagick::COLORSPACE_HSL,
+        Imagick::COLORSPACE_HSB,
+    ];
+
     public function decode(mixed $input): ImageInterface|ColorInterface
     {
         if (!is_object($input)) {
@@ -34,6 +41,13 @@ public function decode(mixed $input): ImageInterface|ColorInterface
             $input = $input->coalesceImages();
         }
 
+        // turn image into rgb if colorspace if other than CMYK, RGB, HSL or HSV.
+        // this prevents working on greyscale colorspace images when loading
+        // from PNG color type greyscale format.
+        if (!in_array($input->getImageColorspace(), self::SUPPORTED_COLORSPACES)) {
+            $input->setImageColorspace(Imagick::COLORSPACE_SRGB);
+        }
+
         // create image object
         $image = new Image(
             $this->driver(),