GeoTIFF files can be raster files containing elevation data, or image files containing color data. Each elevation sample in a raster file is a point in a single FME raster feature, while each pixel color value in an image file is a value in a single FME raster feature.
The reader and writer support most GeoTIFF projections. The writer can also generate an Esri world file with the extension .tfw. GCPs (ground control points) present along with a projection in a GeoTIFF file being read can either be applied to the data as an affine transformation, or stored as properties on the raster geometry.
Cloud Optimized GeoTIFF
FME can read and write Cloud Optimized GeoTIFF (COG) files.
A COG is a regular GeoTIFF file, aimed at being hosted on an HTTP file server, which typically enables more efficient workflows in the cloud. For more information, see the website for Cloud Optimized GeoTIFF.
- To read a COG file from GeoTIFF, enter the URL in the reader dataset parameters.
- To write a COG file from GeoTIFF: After you add the GeoTIFF writer to the workspace, open the Feature Type dialog. Expand the File Structure group and select Layout > Cloud Optimized Tiles.
GeoTIFF/COG Product and System Requirements
|
Format |
FME Platform |
Operating System |
||||
|---|---|---|---|---|---|---|
|
Reader/Writer |
FME Form |
FME Flow |
FME Flow Hosted |
Windows 64-bit |
Linux |
Mac |
|
Reader |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Writer |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Reader Overview
FME considers a single GeoTIFF file to be a dataset.
Writer Overview
FME considers a dataset to be a folder name. The names of the GeoTIFF output files written to the output dataset folder are determined from the FME Feature Type. The folder does not have to exist before the translation occurs. Any existing files in the folder which have the same name are overwritten with the new feature data. The GeoTIFF writer distinguishes duplicate output files by appending numbers to the filenames. Please see "About FME Rasters" for details.
The GeoTIFF writer has an option for setting the bit depth of the output file. The option is exposed as a feature type parameter “Number of Bits Per Cell” on the feature type level and as a feature attribute “geotiff_number_of_bits_per_cell” on the feature level. The value can be set to a value between 1 and 32, or left empty. When a value is specified, the writer will behave as follows:
- The writer checks the interpretation of the input raster bands. The interpretation of the input raster bands must be the minimum power of 2 above the requested bit depth. For example, to write 7-bit data, the interpretation must be one of UINT8, GRAY8, RED8, GREEN8, BLUE8, or ALPHA8.
- The data values on the bands will be reduced to the number of bits specified in the option. Note that values outside the bounds of the bit depth will be capped to the minimum or maximum. For example, if the number of bits is set to 4, a value of 201 (1100 1001 in base 2) will become 15 (1111 in base 2) in the output file.
- The Nodata value on the bands will not change. For example, a Nodata value 201 will still be 201 in the output file whatever the number of bits is set to. The user can change the Nodata value using the RasterBandNodataSetter transformer before writing it to the format.
- The values of the palettes on the input raster will not change, but the number of palette entries does change. The maximum number of palette entries depends on the number of bits in the option. For instance, if the original palette has 256 entries with keys 0 to 255 and the number of bits is set to 4, keys 16 to 255 will be removed and the output palette will only have keys 0 to 15.
BigTIFF Support
Another option in the GeoTIFF writer is BigTIFF support. The option is exposed as a feature type parameter “Enable BigTIFF” on the feature type level, and as a feature attribute geotiff_enable_bigtiff on the feature level.
The value can be set to yes or no, or left empty. When the value is set to no or left empty, the writer functions as if this option does not exist. When the value is set to yes, the writer will produce a file with the BigTIFF file structure. Other applications are required to support BigTIFF in order to open the BigTIFF file, even if the file is less than 4GB.
Writer-Level Format Parameters
The GeoTIFF writer supports additional options through the GeoTIFF Writer Feature Type Parameters.
FME Raster Features
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data.
For comprehensive information about how FME processes raster data, see Rasters.
GeoTIFF files can be written with non-square pixel dimensions.
GeoTIFF supports rasters with an arbitrary number of bands, provided all bands are the same data type and no band has a palette. GeoTIFF also supports rasters with a single band that has a palette.
The reader and writer support band types of Byte, UInt16, Int16, UInt32, Int32, Real32, and Real64. Classified (Paletted) images will return class dictionary (palette) information associated with the band.