Compositing means many things to many people. Whole books have been written on this one topic. Broadly speaking, compositing is the technique and the art of piecing together image parts collected from multiple sources to make a new single whole. If the image is intended to be photo-realistic, a scene that could have really existed, the result is called photo-montage. On the other hand, if the objective is to combine images whose juxtaposition communicates a new idea, the result is called collage.
The main differences between the two are that, for photo-montage, lighting and color matching are very important to the success of the composition. Differences of saturation and value between image elements can ruin the illusion of a montage, as can obvious inconsistencies in lighting. It is also important to pay attention to various other visual cues; however, the objective of this chapter is not to provide a complete discussion of these topics. Rather, the goal is to demonstrate the use of the GIMP in several projects and show how the GIMP's tools can be used to solve collage and photo-montage problems.
Regardless of whether a project is photo-montage or collage, the main elements of compositing consist of selections, copy and paste operations, and positioning of image elements. The finer aspects require blending, color matching, and general attention to detail. Thus, most of the GIMP skills needed for compositing have already been discussed in previous chapters. Indeed, this chapter presumes the reader is familiar with concepts presented in earlier chapters. The projects presented here are not described in minute detail. Rather, when techniques that have been described in earlier chapters are required, the reader is referred to the appropriate section of the book. Although this chapter is mostly project oriented, some new GIMP tools are also introduced.