I keep running in to this problem, and I have been just avoiding assets that don’t use a uniform sprite size. However, I just found out about the Liberated Pixel Cup assets, and a great little generator at sanderfrenken.github.io and I love them, but they have this problem.
Basically, it’s that the size of individual frames can be different. For the LPC assets and the output of the generator, most frames are 64x64px and the character is positioned correctly inside of that. However, to make room for the sword, for example, the sword attack animation frames are much larger.
What that means, as far as I’m aware, is that I can’t use the Grid By Cell Size or Automatic options to slice, and I have to set the pivot for each frame manually, so that the sprite doesn’t shift when I change animations.
What I’m doing now is choosing a reference point (the shadow in this example) and manually trying to place the pivot point in the center of that, but it’s very time consuming, and I can’t help think there is a better way to handle this that I’m just not aware of.
Thanks