code: protected function getBackground(array $setColor = [])
      {
          if ($setColor) {
              return imagecolorallocate(
                  $this->resource,
                  $setColor[0],
                  $setColor[1],
                  $setColor[2]
              );
          }
  
          return imagecolorallocatealpha(
              $this->resource,
              0,
              0,
              0,
              127
          );
      }
docs: @param array $setColor
  
  @return int