2. Review of Layers
The GIMP is a pixel-based image manipulation tool, but from the
perspective of creative composition with digital images,
pixels are neither the most convenient nor the most
important component to work with. This honor is reserved for layers.
Pixels are the basic stuff of layers, and layers are stacked to make
images. This constitutes a hierarchy of scale. Pixels are small,
which makes them too hard to work with. It would be difficult to
build an image if it had to be done pixel-by-pixel. On the other
hand, whole images are too unwieldy to work with comfortably. There
are conceptual parts or particular components of images we want to
work with without disturbing the rest. By constructing an image out
of layers, it is possible to work with each component independently of
the rest of the image. This makes layers the happy medium between
pixels and images. They are ``right-sized'' for what we want to
accomplish in the GIMP.
The images we want to make are usually constructed of conceptual
pieces from other images: a part from here and there that we stitch
together into a single whole. Layers allow us to combine all the
pieces yet keep them separate. This collage view of working with
digital images is extremely powerful. We can work on individual image
pieces without affecting the others. Having the parts on separate
layers allows for their separate processing. Layers can be
positioned, repositioned, color-adjusted, and filtered independently.
It is difficult to over-emphasize the utility of layers. Compositing,
animation, selections, effects, and enhancements are all made easier
because of layers.
The objective of this chapter is to develop a firm foundation for
layer mechanics. You will learn how to use them effectively while
avoiding common pitfalls. The material covered here will be referred
to often in later chapters.