7 Raster functions

 

This chapter covers

  • Constructor functions
  • Output functions
  • Raster band and pixel accessors and setters
  • Georeferencing functions
  • Reclassing functions
  • Polygonizing functions

The raster type is different in makeup from the geometry type covered in chapter 6. Geometries model an object as a set of linear equations, whereas rasters model an object as a tapestry of cells. In PostGIS, you’ll find the two types working together, leveraging each other’s strengths. For example, you can output a geometry in a raster file format such as PNG. You can also clip raster images with vector boundaries. We’ll touch on raster processing in this chapter, but we’ll leave the more-thorough treatment for chapter 12, where we’ll demonstrate advanced raster-processing functions, such as raster aggregate functions, map algebra functions, and set-returning functions.

7.1 Raster terminology

7.2 Raster constructors

7.2.1 Converting geometries to rasters with ST_AsRaster

7.2.2 Loading rasters with raster2pgsql

7.2.3 Constructing rasters from scratch: ST_MakeEmptyRaster and ST_AddBand

7.2.4 Setting pixels: ST_SetValue and ST_SetValues

7.2.5 Creating rasters from other rasters

7.2.6 Converting other raster formats with ST_FromGDALRaster

7.3 Raster output functions

7.3.1 ST_AsPNG, ST_AsJPEG, and ST_AsTiff

7.3.2 Output using ST_AsGDALRaster

7.3.3 Using psql to export rasters

7.4 Raster accessors and setters

7.4.1 Basic raster metadata properties