Select "Erase by Color" and tap the background you want to erase. Areas of a similar colour that are connected to the spot you tapped will be erased all at once. You can adjust how much is erased with the "Color Range" slider.
Select "Erase by Color" and tap the background you want to erase. Areas of a similar colour that are connected to the spot you tapped will be erased all at once. You can adjust how much is erased with the "Color Range" slider.