# JP2ECW -- ERDAS JPEG2000 (.jp2)

GDAL supports reading and writing JPEG2000 files using the ERDAS ECW/JP2 SDK developed by Hexagon Geospatial (formerly Intergraph, ERDAS, ERMapper). Support is optional and requires linking in the libraries available from the ECW/JP2 SDK Download page.

Coordinate system and georeferencing transformations are read, and some degree of support is included for GeoJP2 (tm) (GeoTIFF-in-JPEG2000), ERDAS GML-in-JPEG2000, and the new GML-in-JPEG2000 specification developed at OGC.

### Licensing

The ERDAS ECW/JP2 SDK v5.x is available under multiple license types. For Desktop usage, decoding any sized ECW/JP2 image is made available free of charge. To compress, deploy on a Server platform, or decode unlimited sized files on Mobile platforms a license must be purchased from Hexagon Geospatial.

### History

- v3.x - Last release, 2006
- v4.x - Last release, 2012
- v5.x - Active development, 2013 - current

## Georeferencing

Georeferencing information can come from different sources : internal (GeoJP2 or GMLJP2 boxes), worldfile .j2w/.wld sidecar files, or PAM (Persitant Auxiliary metadata) .aux.xml sidecar files. By default, information is fetched in following order (first listed is the most prioritary): PAM, GeoJP2, GMLJP2, WORLDFILE.

Starting with GDAL 2.2, the allowed sources and their priority order can be changed with the GDAL_GEOREF_SOURCES configuration option (or GEOREF_SOURCES open option) whose value is a comma-separated list of the following keywords : PAM, GEOJP2, GMLJP2, INTERNAL (shortcut for GEOJP2,GMLJP2), WORLDFILE, NONE. First mentioned sources are the most prioritary over the next ones. A non mentioned source will be ignored.

For example setting it to "WORLDFILE,PAM,INTERNAL" will make a geotransformation matrix from a potential worldfile prioritary over PAM or internal JP2 boxes. Setting it to "PAM,WORLDFILE,GEOJP2" will use the mentioned sources and ignore GMLJP2 boxes.

## Option Options

(GDAL >= 2.0 ) The following open option is available:

- 1BIT_ALPHA_PROMOTION=YES/NO: Whether a 1-bit alpha channel should be promoted to 8-bit. Defaults to YES.

- GEOREF_SOURCES=string: (GDAL > 2.2) Define which georeferencing sources are allowed and their priority order. See Georeferencing paragraph.

## Creation Options:

Note: Only Licensing and compression target need to be specified. The ECW/JP2 SDK will default all other options to recommended settings based on the input characteristics. Changing other options can substantially impact decoding speed and compatibility with other JPEG2000 toolkits.

- LARGE_OK=YES: (v3.x SDK only) Allow compressing files larger than 500MB in accordance with EULA terms. Deprecated since v4.x and replaced by ECW_ENCODE_KEY & ECW_ENCODE_COMPANY.

- ECW_ENCODE_KEY=key: (v4.x SDK or higher) Provide the OEM encoding key to unlock encoding capability up to the licensed gigapixel limit. The key is approximately 129 hex digits long. The Company and Key must match and must be re-generated with each minor release of the SDK. It may also be provided globally as a configuration option.

- ECW_ENCODE_COMPANY=name: (v4.x SDK or higher) Provide the name of the company in the issued OEM key (see ECW_ENCODE_KEY). The Company and Key must match and must be re-generated with each minor release of the SDK. It may also be provided globally as a configuration option.

- TARGET=percent: Set the target size reduction as a percentage of the original. If not provided defaults to 75 for an 75% reduction. TARGET=0 uses lossless compression.

- PROJ=name: Name of the ECW projection string to use. Common examples are NUTM11, or GEODETIC.

- DATUM=name: Name of the ECW datum string to use. Common examples are WGS84 or NAD83.

- GMLJP2=YES/NO: Indicates whether a GML box conforming to the OGC GML in JPEG2000 specification should be included in the file. Unless GMLJP2V2_DEF is used, the version of the GMLJP2 box will be version 1. Defaults to YES.

- GMLJP2V2_DEF=filename: (Starting with GDAL 2.0) Indicates whether a GML box conforming to the OGC GML in JPEG2000, version 2 specification should be included in the file. filename must point to a file with a JSon content that defines how the GMLJP2 v2 box should be built. See GMLJP2v2 definition file section in documentation of the JP2OpenJPEG driver for the syntax of the JSon configuration file. It is also possible to directly pass the JSon content inlined as a string. If filename is just set to YES, a minimal instance will be built.

- GeoJP2=YES/NO: Indicates whether a UUID/GeoTIFF box conforming to the GeoJP2 (GeoTIFF in JPEG2000) specification should be included in the file. Defaults to YES.

- PROFILE=profile: One of BASELINE_0, BASELINE_1, BASELINE_2, NPJE or EPJE. Review the ECW SDK documentation for details on profile meanings.

- PROGRESSION=LRCP/RLCP/RPCL: Set the progression order with which the JPEG2000 codestream is written. (Default, RPCL)

- CODESTREAM_ONLY=YES/NO: If set to YES, only the compressed imagery code stream will be written. If NO a JP2 package will be written around the code stream including a variety of meta information. (Default, NO)

- LEVELS=n: Resolution levels in pyramid (by default so many that the size of the smallest thumbnail image is 64x64 pixels at maximum)

- LAYERS=n: Quality layers (default, 1)

- PRECINCT_WIDTH=n: Precinct Width (default, 64)

- PRECINCT_HEIGHT=n: Precinct Height (default 64)

- TILE_WIDTH=n: Tile Width (default, image width eg. 1 tile). Apart from GeoTIFF, in JPEG2000 tiling is not critical for speed if precincts are used. The minimum tile size allowed by the standard is 1024x1024 pixels.

- TILE_HEIGHT=n: Tile Height (default, image height eg. 1 tile)

- INCLUDE_SOP=YES/NO: Output Start of Packet Marker (default false)

- INCLUDE_EPH=YES/NO: Output End of Packet Header Marker (default true)

- DECOMPRESS_LAYERS=n: The number of quality layers to decode

- DECOMPRESS_RECONSTRUCTION_PARAMETER=n: IRREVERSIBLE_9x7 or REVERSIBLE_5x3

- WRITE_METADATA=YES/NO: (GDAL >= 2.0) Whether metadata should be written, in a dedicated JP2 XML box. Defaults to NO. The content of the XML box will be like:

      <GDALMultiDomainMetadata>
        <Metadata>
          <MDI key="foo">bar</MDI>
        </Metadata>
        <Metadata domain='aux_domain'>
          <MDI key="foo">bar</MDI>
        </Metadata>
        <Metadata domain='a_xml_domain' format='xml'>
          <arbitrary_xml_content>
          </arbitrary_xml_content>
        </Metadata>
      </GDALMultiDomainMetadata>

  If there are metadata domain whose name starts with "xml:BOX_", they will be written each as separate JP2 XML box.

  If there is a metadata domain whose name is "xml:XMP", its content will be written as a JP2 UUID XMP box.

- MAIN_MD_DOMAIN_ONLY=YES/NO: (GDAL >= 2.0) (Only if WRITE_METADATA=YES) Whether only metadata from the main domain should be written. Defaults to NO.

"JPEG2000 format does not support creation of GDAL overviews since the format is already considered to be optimized for "arbitrary overviews". JP2ECW driver also arranges JP2 codestream to allow optimal access to power of two overviews. This is controlled with the creation option LEVELS."

## Configuration Options

The ERDAS ECW/JP2 SDK supports a variety of runtime configuration options to control various features. Most of these are exposed as GDAL configuration options. See the ECW/JP2 SDK documentation for full details on the meaning of these options.

- ECW_CACHE_MAXMEM=bytes: maximum bytes of RAM used for in-memory caching. If not set, up to one quarter of physical RAM will be used by the SDK for in-memory caching.

- ECW_TEXTURE_DITHER=TRUE/FALSE: This may be set to FALSE to disable dithering when decompressing ECW files. Defaults to TRUE.

- ECW_FORCE_FILE_REOPEN=TRUE/FALSE: This may be set to TRUE to force open a file handle for each file for each connection made. Defaults to FALSE.

- ECW_CACHE_MAXOPEN=number: The maximum number of files to keep open for ECW file handle caching. Defaults to unlimited.

- ECW_AUTOGEN_J2I=TRUE/FALSE: Controls whether .j2i index files should be created when opening jpeg2000 files. Defaults to TRUE.

- ECW_RESILIENT_DECODING=TRUE/FALSE: Controls whether the reader should be forgiving of errors in a file, trying to return as much data as is available. Defaults to TRUE. If set to FALSE an invalid file will result in an error.

## Metadata

Starting with GDAL 1.11.0, XMP metadata can be extracted from JPEG2000 files, and will be stored as XML raw content in the xml:XMP metadata domain.

ECW/JP2 SDK v5.1+ also advertises JPEG2000 structural information as generic File Metadata reported under "JPEG2000" metadata domain (-mdd):

- ALL_COMMENTS: Generic comment text field

- PROFILE: Profile type (0,1,2). Refer to ECW/JP2 SDK documentation for more info

- TILES_X: Number of tiles on X (horizontal) Axis

- TILES_Y: Number of tiles on Y (vertical) Axis

- TILE_WIDTH: Tile size on X Axis

- TILE_HEIGHT: Tile size on Y Axis

- PRECINCT_SIZE_X: Precinct size for each resolution level (smallest to largest) on X Axis

- PRECINCT_SIZE_Y: Precinct size for each resolution level (smallest to largest) on Y Axis

- CODE_BLOCK_SIZE_X: Code block size on X Axis

- CODE_BLOCK_SIZE_Y: Code block size on Y Axis

- PRECISION: Precision / Bit-depth of each component eg. 8,8,8 for 8bit 3 band imagery.

- RESOLUTION_LEVELS: Number of resolution levels

- QUALITY_LAYERS: Number of quality layers

- PROGRESSION_ORDER: Progression order (RPCL, LRCP, CPRL, RLCP)

- TRANSFORMATION_TYPE: Filter transformation used (9x7, 5x3)

- USE_SOP: Start of Packet marker detected (TRUE/FALSE)

- USE_EPH: End of Packet header marker detected (TRUE/FALSE)

- GML_JP2_DATA: OGC GML GeoReferencing box detected (TRUE/FALSE)

- COMPRESSION_RATE_TARGET: Target compression rate used on encoding

## See Also

- Implemented as `gdal/frmts/ecw/ecwdataset.cpp`.

- ECW/JP2 SDK available at www.hexagongeospatial.com
- Further product information available in the User Guide
- Support for non-GDAL specific issues should be directed to the Hexagon Geospatial public forum
- GDAL ECW Build Hints