Easy tool to decompose sprite image?

This program is pretty good at decomposing sprites into individual frames

https://github.com/ForkandBeard/Alferd-Spritesheet-Unpacker

it supports all standard bitmap formats, .png, .bmp, .gif, .tiff and does everything pretty much automatically.

This one worked nicely for me to extract images from jquery ui sprites http://renderhjs.net/shoebox/

Use the slice tool in Photoshop:

1. Use the slice select tool (note the select part of that, see screenshot).
2. Right-click anywhere on the canvas and select Divide Slice... from the drop down menu.
3. Enter in the height/width or sprite multiple.
4. Once finished, go to save for web and devices...
5. When you save, this will export all the individual cutouts to the file format of your choosing in a separate folder.

If they are of uneven size (not on a grid) you can also select them individually with the vanilla 'slice select' tool. If you have a lot of similar grids, save everything as a photoshop action and batch process them.

I encountered a similar problem after losing the source images for a sprite and built this relatively simple tool: https://github.com/fmovlex/desprite

Hope this helps.