RasterLite2 - Rasters in SQLite DB

Starting with GDAL 2.2, the SQLite driver allows reading and writing SQLite databases containing RasterLite2 coverages.

Those databases can be produced by the utilities of the RasterLite2 distribution, such as rl2tools.
The driver supports reading grayscale, paletted, RGB, multispectral images stored as tiles in the many compressed formats supported by libRasterLite2. The driver also supports reading overviews/pyramids, spatial reference system and spatial extent.

GDAL/OGR must be compiled with sqlite support and against librasterlite2 and libspatialite.

The driver is implemented a unified SQLite / SpatiaLite / RasterLite2 vector and raster capable driver./p>

Opening syntax

A RasterLite2 filename can be specified as the connection string. If the file contains a single RasterLite2 coverage, this one will be exposed as the GDAL dataset. If the file contains multiple coverages, each one will be exposed as a subdataset with the syntax RASTERLITE2:filename:coverage_name. See the basic concepts of RasterLite2.

If a coverage is made of several sections, they will be listed as subdatasets of the coverage dataset, so as to be accessed individually. By default, they will be exposed as a unified dataset. The syntax of section-based dataset is RASTERLITE2:filename:coverage_name:section_id:section_name.

Creation

The driver supports creating new databases from scratch, adding new coverages to an existing database and adding sections to an existing coverage.

Creation options

APPEND_SUBDATASET=YES/NO: Whether to add the raster to the existing file. If set to YES, COVERAGE must be specified. Default is NO (ie overwrite existing file)
COVERAGE=string: Coverage name. If not specified, the basename of the output file is used.
SECTION=string: Section name. If not specified, the basename of the output file is used.
COMPRESS=NONE/DEFLATE/LZMA/PNG/CCITTFAX4/JPEG/WEBP/CHARS/JPEG2000: Compression method. Default is NONE. See the information about supported codecs. Note that some codecs may not be available depending on how librasterlite2 has been built.
QUALITY=0 to 100: Image quality for JPEG, WEBP and JPEG2000 compressions. Exact meaning depends on the compression method. For WEBP and JPEG2000, the value 100 triggers the use of their lossless variants.
PIXEL_TYPE=MONOCHROME/PALETTE/GRAYSCALE/RGB/MULTIBAND/DATAGRID: Raster pixel type. Determines the photometric interpretation. See the information about supported pixel types. The driver will automatically determine an appropriate pixel type given the band characteristics.
BLOCKXSIZE=int_value. Block width. Defaults to 512.
BLOCKYSIZE=int_value. Block height. Defaults to 512.
NBITS=1/2/4. Force bit width. This will be by default gotten from the NBITS metadata item in the IMAGE_STRUCTURE metadata domain of the source raster band.
PYRAMIDIZE=YES/NO. Whether to build automatically build relevant pyramids/overviews. Defaults to NO. Pyramids can be built with the BuildOverviews() / gdaladdo.

Examples

Reading a RasterLite2 database with a single coverage:
```
gdalinfo my.rl2
```
Listing the subdatasets corresponding to the coverages of a RasterLite2 database with several coverages:
```
gdalinfo multiple_coverages.rl2
```

Reading a subdataset corresponding to a coverage:

gdalinfo RASTERLITE2:multiple_coverages.rl2:my_coverage

Creating a RasterLite2 dataset from a grayscale image:
```
gdal_translate -f SQLite byte.tif byte.rl2
```
Creating a RasterLite2 dataset from a RGB image, and using JPEG compression:
```
gdal_translate -f SQLite rgb.tif rgb.rl2 -co COMPRESS=JPEG
```

Adding a RasterLite2 coverage to an existing SpatiaLite/RasterLite2 database:

gdal_translate -f SQLite rgb.tif rgb.rl2 -co APPEND_SUBDATASET=YES -co COVERAGE=rgb

Adding pyramids to a coverage:
```
gdaladdo rgb.rl2 2 4 8 16
```