Image Styles file is not simply a bitmap, it is a set of sequential effects what you can modify at any time. In the usual graphics editor after long hours of tests you each time repeat the same operations spending on this huge amount of time. Image Styles will save you of these problems. For example at any moment you may return to the first operation so that change something and see as it will be looked, if it was not pleasant a pair of pressing keys and all comes back, there is no necessity to make all operations again! It is not trick it is modern technologies.

Open "button.isf" example file and try to move scroll bar of Plasma's "Variant" parameter (in "Script" window). After that we see that only the colourful background on the button has varied and the rest remained without changes.

Variant: 9005

Variant: 9004

Variant: 9006

For practice try to change parameters in other Image Styles files.