Resampling of raster is a technique that is used to create a new version of the raster dataset with a different height and width. Resample tool can be used to increase or decrease the raster size. If you decrease the cell size it will enlarge the raster size and the resultant raster output. If you increase the raster size, its called upsampling. If you decrease the size, its called downsampling. In short, you will create a new raster cell grid on a different alignment from the original raster.
The values for each cell in the new raster grid are calculated by sampling or interpolating with the values of a neighborhood of cells in the corresponding position of the original input grid. This process introduces some visual artifacts in the output raster like aliasing, blurring, and edge halos. To minimize the effects of these artifacts, MapInfo Pro Advanced uses the resampling methods.
Supported Resampling Methods.
- Nearest Neighbor - In this method, the cell value of the resampled raster dataset is determined by taking the value of nearest input cell. This method is useful when you reproject a raster dataset and you want to retain the original cell values. You can use Nearest Neighbor resampling for raster maps, grids, and scanned maps to get faster results. Nearest Neighbor is used for discrete data, such as a land-use classification.
- Bilinear - In this method, the cell value of the resampled raster dataset is calculated based on the value of the linear distance-weighted average of 4 surrounding cells of the input raster.
- Bi-cubic - In this method, the cell value of the resampled raster dataset is calculated based on the weighted value 16 surrounding cells of the input raster. This method requires more processing time but gives more accurate result than bilinear interpolation. This method is useful when you want to reduce aliasing and blurring of raster images.
In MapInfo Pro Advanced, you can resample classified and numeric rasters. If the source raster is of classified type, you can produce a resampled output in MRR or classified formats. For example, if source raster is of type Vertical Mapper GRC, then the available output types are MRR and GRC. Imagery type rasters are also supported.
You can also use this operation in batch processing mode.
Support for MapInfo Virtual Raster
A MapInfo virtual raster is a raster that can be loaded, displayed, and operated upon in MapInfo Pro just like any other raster format. The raster data is acquired or generated on-demand, at run time. The MapInfo Virtual Raster (MVR) is a simple XML file using the .MVR file extension that you can load in MapInfo Pro. As a result, this operation is fast, and you get a preview without generating an actual output Raster file. You see the results instantaneously on a mapper. This option is also available in the Batch mode.
- Input - Input File - The input files allowed for an MVR output are limited to those having Continuous and Imagery field types.
- Resample Options - Resample Method - This option is not supported and hence hidden in case of an MVR output.
- Output - Compression Settings - This option is not applicable and hence hidden in case of an MVR output.