HI there!~...Welcome to the forums..
Are you asking for a 'software' that takes a given sprite sheet..and automatically cuts all sprites-- and their given angles--chooses color for transparency....names them accordingly..and saves them all at once..sort of thing..?
lol...That would be nice...
However It shouldn't be too hard working with a sprite sheet....once u figure out the area/color for transparency..[that being something that is not in the sprite] and all angles are in order~
You could crop one sprite/angle at a time--In paint for instance...Open it up in Gimp[whatever supports .gifs]
Choose the color of transparency...name it[accordingly] and save as .gif--
I make it sound easy...

...I have heard Paint is the easiest place to work with sprite sheets..
I only tried it once..And the angles weren't in order..It was h*ll...but had it been in order..I think it would have endured it....or..maybe not..lol..
And there can't be a hundred colors in the sprite..It has to be limited..Otherwise figuring out transparency...its really....trying..--for lack of a better word..lol