How to remove the background that is cut out along with the character from a png sprite sheet?

Question

Canvas

How to remove the background that is cut out along with the character from a png sprite sheet? Found a database of sprites on the net. Downloaded a png file with some orc. There are no problems with animation using drawImage(), but here's the problem: together with the hero, his background is also cut out and he moves in his square. How to "untie" the characters from their background. Game development books don't cover this topic. I would like to get step-by-step instructions, for example, using a photo-shop.