Raster or channel layers (IMG)

Image data are referred to as channels or raster layers in a GDB database. The raster layers or channels are numbered, starting at one, and a GDB database can have zero or more raster layers. Each raster layer consists of a rectangular grid, or array, of digital numbers.

All raster layers in a particular database must have the same size. Size is usually reported as width in pixels, and height in lines. Furthermore, all raster layers correspond to the same real world region, which is further discussed in the georeferencing section.

The following is a conceptual example of a three-channel GDB database that contains only two lines, each three pixels wide (2x3).

                 3 pixels wide
                +-------+
                | C C C |
                | C C C | <--- channel 3 
                +-------+
              +-------+
              | B B B |
              | B B B |  <--- channel 2 
              +-------+ 
            +-------+ 
 Line 1->   | A A A |
 Line 2-&   | A A A |  <--- channel 1 
            +-------+

Note: 8, 16 and 32-bit integer image types are supported for reading and writing. Because 32-bit integer images are represented in GDB as 32-bit real images, however, some loss of precision may occur.