These instructions are for making a two color explosion.
Go to ImageMagick. Scroll down and enter 150x150 in Size, change Format to xc and for Meta, enterblack. Click Output. Save it in an empty directory and name it 1.gif
Chose Draw. For Primitive, select Circle. For Cooridinates, enter +75+ 55 +75+85. For Color, enter red. For Stroke Color, enter white. For Stroke Color, enter 3. You should now have a red circle in the middle with a white ring around it.
The next steps will add to the number colors and file size. If you limit the colors now, your finished product will load faster. Select Colormap and set it to 32 colors or less.
Select Effects and select Spread. For parameter, enter 10x10. Save it your temporary directory as 2.gif.
Repeat the Spread step and store as 3.gif. Do it three more times so you have six .gif's. Numbered in the order of the amount of spread.
Get the URL of the Directory. Note: The URL should end in a /".
Go back to ImageMagick. Scroll down to the bottom. If the Format is still xc, change it back to Implicit or the next steps will not work.
Enter the directory URL.
Go to Colormap and reduce the colors again.
Go to Output. For Format select .gif and for Storage Type select mulit-frame file. If you out put it as it is now, it will be really fast so enter 20 in the Delay box if you want it to be a little slower.
