You can control the reprojection options of your vector and raster maps using the Image Processing Preference. Reprojection, particularly when reprojecting seamless tables or other large raster map layers, can take a long time. This is particularly true if your reprojection is dramatic, as when you are transforming world-wide rasters from Long/Lat to Mercator, for example.
To see the results of this setting, refer to Reprojecting a Raster based on a Vector Map.
To set the raster reprojection options for all registered raster
files:
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On the PRO tab, click Options, and Image Processing to open the Image Processing dialog box.
You can also open the Image Processing dialog box by clicking Image Processing in the Map Options dialog box (under the MAP tab).
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Choose a reprojection:
- Never - Prevents raster reprojection. This is the default setting which preserves the pre-version 8.5 MapInfo Pro behavior.
- Always - Ensures that reprojection is always performed, that is, MapInfo Pro calculates the image's coordinates based on a precise formula and then the pixels are resampled using Cubic Convolution or Nearest Neighbor options.
- Optimized - Determines the reprojection of a raster image based on the look of the destination rectangle (a selection of the image) after transformation into the source image space. If it looks as a rigorous rectangle (two sides are parallel to x-axis and two sides parallel to y-axis), then the standard Windows functions stretch the source image in both directions, as it was in pre-version 8.5 MapInfo Pro. If the image fails the rigorous rectangle test, the reprojection is performed using the resampling options.
The Resampling Method options enable when you select Always or Optimized. Never is the default reprojection option and reflects the vector reprojection only behavior.
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If you chose Always or Optimized,
then you can decide how best to resample the image by choosing:
- Cubic Convolution provides the best restoration of pixel values because of their separateness. Using this option, a pixel in the destination image is calculated based on the pixel values in a 4x4 pixel window centered at the original pixel in the source image. The coordinates of the original pixel are calculated for every pixel of the destination image based on a special optimized procedure. Pixels are then weighted based on the basic pixel coordinates. In general, we recommend you use the Cubic Convolution resampling method for aerial images and satellite raster images to get a better image quality. The Cubic Convolution algorithm used in MapInfo Pro is based on the work of S.K. Park and R.A. Schowengerdt, Computervision, Graphics and Image Processing (1983, Volume 23. Pages 258-272).
- Nearest Neighbor replaces the pixel value in the reprojected image with the original pixel value from the source image. This resampling method takes less time to render than the Cubic Convolution method, but may be less precise. In general we recommend you use Nearest Neighbor resampling for raster maps, grids, and scanned maps to get faster results.
Note: When you are reprojecting 8-bit palette raster images, such as color .TIFF or .BMP images, MapInfo Pro uses the Nearest Neighbor resampling option without regard to the resampling method you choose.
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Click OK to close the dialog and save your settings.
When you choose the Always or Optimized reprojection, the reprojection process runs in the background and there is nothing to see. However, you can see the differences that Cubic Convolution or Nearest Neighbor resampling make in the way that the raster displays.