Replace collage generation by own implementation

1. +++ b/src/ThumbnailGenerator.php
   @@ -0,0 +1,208 @@
   +  public function createImage(array $images) {
   

   Function should be called something more obvious like createThumbnail(), createCollage() or simply create().

2. +++ b/src/ThumbnailGenerator.php
   @@ -0,0 +1,208 @@
   +    $int = hexdec($this->backgroundColor);
   +    $arr = [
   +      "red" => 0xFF & ($int >> 0x10),
   +      "green" => 0xFF & ($int >> 0x8),
   +      "blue" => 0xFF & $int,
   +    ];
   +
   

   Use Drupal/Component/Utility/Color class

3. +++ b/src/ThumbnailGenerator.php
   @@ -0,0 +1,208 @@
   +    switch (count($loaded_images)) {
   

   What happens when this is called with an empty array? It seems like 'default' case will fail badly.

1. +++ b/src/Plugin/media/Source/Slideshow.php
   @@ -197,12 +216,12 @@ class Slideshow extends MediaSourceBase implements MediaSourceEntityConstraintsI
   +      ->setPadding(2)
   

   Add moar padding (10).

2. Needs tests.

Looks very nice !!! Thanks a lot for the quick response on the issue. Agree with #8 that it needs more padding

#12 seems fine