Description

Wikipedia defines rasters as "a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Raster images are stored in image files with varying formats (see Comparison of graphics file formats)."



By its nature, raster is very different from vector. There are no separate features on a raster image such as houses, roads, or elevation points. The raster itself is a single feature. All the details that we see on the rasters is only our perception of the differently colored pixels. On the picture below, there are two layers, one of them is a raster, and another - is a vector. In full extents they may look indentical, however, no matter how close we zoom in, we always see the vector polygons representing buildings, whereas raster buildings turn into chains of points:



This is why rasters "live" in their own world, have their own formats, and often need separate transformation tools. Still, this world is not isolated from the rest of the spatial universe - rasters can interact with vectors in many different ways. Many transformations work with both rasters and vectors, vectors can be rasterized, and features can be extracted from rasters. There is even a way to combine them in single feature by using rasters as textures.

FME is an extremely powerful tool for all these operations. Exclusively vector system in the past, now FME easily can handle multiple raster formats and change them with dozens of transformers in a quick, and efficient way, exposing very rich set of options.

See the attached Understanding Rasters.pdf - written by one of our Coop students - for details on the internals of a raster.