Merging one image into another (Compositing) may involve changing the background in the key image or adding texture to that image. Photographers typically use photo editors such as Photoshop to create these images. Though this can produce very creative and interesting images, it can also become very time consuming with uncertain results. An alternative is Greenscreen (Chromakey) photography.
Greenscreen techniques are common in videography, but can also be used effectively with traditional photography. The subject is photographed in front of a green background after which these images are loaded into a software program. The background or texture chosen then replaces the green background though a technique known as "Keying". Greenscreen photography can also add realistic features to an image that may be cost prohibitive to the project.
Plug-ins are available for a variety of image editing programs, as well as stand alone programs such as Photokey (FXhome) or Greenscreen wizard.