Images and Image Display
Julio Sanchez, Maria P. Canton, William Perrizo · 2018
A digital image consists of a set of numeric values representing image brightness. Although photographic sensors play an important role in conventional remote sensing technology, most imagery acquired by spacecraft is either in digital form, or is digitized soon after its acquisition. Perhaps the most interesting feature of digitally encoded image data is that the image can be analytically manipulated. Several practical considerations determine the best way by which to implement the digital representation. The digital numbers (DN) of a scene are a set of scaled values that encode the relative brightness of each screen pixel. The DNs are a useful tool in encoding, transmitting, and displaying scene information; however, they also have some intrinsic limitations. The raw pixel data is a set of digital values that represent radiation intensity values of the original image. The raw data is usually accompanied by its corresponding metadata file, which holds the general image information necessary for processing and displaying operations.