superimposing

Superimposing, in general, refers to the act of placing one image, signal, or dataset on top of another so that both are visible in a single composite. In imaging and computer graphics, it is achieved by aligning the elements to a common coordinate system and blending their pixel values, often using transparency (alpha blending). In a broader sense, the term also appears in the study of linear systems, where the superposition principle states that the resultant effect is the sum of the individual effects.

In photography and film, superimposing enables double exposure, compositing, and overlays, allowing elements from separate frames to coexist in a single scene. In graphic design, layers and masks control how images are stacked and revealed.

In medicine, image fusion or multimodal superimposition combines data from different modalities, such as CT and MRI, to provide complementary information for diagnosis, planning, or image-guided procedures. In astronomy and remote sensing, overlays help compare datasets, such as aligning maps with satellite imagery.

Techniques include layering, alpha blending, and chroma keying, as well as feature-based registration to correct misalignment between sources. The quality of a superimposed result depends on spatial alignment, resolution matching, and color/contrast compatibility. Numerous software tools support these operations, ranging from graphic editors to specialized medical imaging platforms.

Ethical and perceptual considerations include avoiding misleading composites, ensuring proper attribution when images are sourced from multiple origins, and clearly communicating the level of transparency or fusion used in the final image.