0, 0 (0): blocks/redstone_block.png from Minecraft 1.7.10
0, 1 (1): items/hopper.png from Minecraft 1.7.10
1, 0 (16): blocks/hopper_inside.png from Minecraft 1.7.10
1, 1 (17): blocks/hopper_outside.png from Minecraft 1.7.10
1, 2 (18): blocks/hopper_top.png from Minecraft 1.7.10

All textures originate from Mojang.