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 ...

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