RasterDgn Makes it Easy to Permanently Deskew Raster Reference Files

Change the actual raster reference file, not just the way it displays in one DGN file.

By Eiren Smith
Do you have crooked raster reference files of scanned drawings? Do you find yourself rotating the same raster reference file in MicroStation every time you attach that raster file to another DGN file? MicroStation's Raster Manager doesn't change the actual raster file, it just changes how it displays in that one instance in the current DGN file, meaning the deskewing is never permanent as the raster file itself doesn't get changed. So, every time you attach the raster reference file, you also have to manually deskew it again with MicroStation's Raster Manager.

MicroStation Deskew Raster

Figure 1. Each of RasterDgn’s features such as deskew, copy (shown above), move, delete and more are easy to use. Once you know how to use one, you can use them all. RasterDgn is the easiest way to edit your raster reference files without leaving MicroStation.

This kind of double-work is completely avoidable. Axiom's RasterDgn can deskew the actual raster file such as a TIFF or CIT (a common Intergraph raster file format) file so you never have to fix its rotation in MicroStation again. You deskew it once with RasterDgn and it stays deskewed because RasterDgn changes the actual raster file, not just how it is displayed as referenced to one DGN file. Even better, RasterDgn doesn't require you to figure out the angle you need to deskew by to make the raster file level — RasterDgn can scan the raster file and calculate its skew angle completely automatically.

We hear from customers all the time with scanned drawings that are skewed. It's a common side effect of scanning large batches of old drawings, especially if the folks scanning them used an automatic document feeder to speed up the scanning job. And when people need to scan tens of thousands of drawings, they do whatever they can to save time. Sometimes this results in 100,000 skewed raster files. Rescanning the skewed drawings would be way too costly, and carefully rotating them by hand each time they're attached to a DGN file, over and over, is tedious and error-prone.

Deskewing a Referenced Raster File with RasterDgn
RasterDgn makes short work of this. Here's how.

  1. Open a DGN file with a skewed raster reference file attached in Micro­Station. RasterDgn supports MicroStation V8 2004 Edition, XM and V8i. For this example, I'll use the tutorial sample file "rasdgn.dgn" delivered with RasterDgn, which is usually saved in "c:\Program Files\Axiom\V8\RasDgn\Sample\". Observe that it is indeed skewed.
  2. Select Axiom | RasterDgn for V8 from the Axiom menu.
  3. Choose the {Deskew} button from the RasterDgn toolbar. The "RasterDgn Deskew" tool settings box will appear.

MicroStation Deskew Raster

Figure 2. RasterDgn’s Deskew tool can determine the exact skew angle of your raster reference file. You can choose the corner to pivot about when deskewing.

Note: In addition to automatic calculation, RasterDgn allows you to enter a skew angle value or use a two-points method. For this example, we'll use the default ("Calculate automatically") as it actually does an incredibly precise job. Also note the "Pivot Corner" setting, which lets you choose the corner to pivot the raster file about when deskewing it. I'll leave the default corner chosen, "Left-Top".

  • If you have only one raster reference file attached to your active DGN file, RasterDgn will immediately calculate its skew angle and report it in its tool settings box. If you have multiple raster reference files attached to your active DGN file, choose the one you want to deskew with a data point and RasterDgn will calculate its skew angle.
  • Once RasterDgn has calculated the raster file's skew angle, place a data point anywhere in any view and RasterDgn will deskew the attached raster file. When it is done, you will see the deskewed raster file in MicroStation immediately — there is no need to reopen your DGN file to reload the deskewed raster file. It just works.

MicroStation Deskew Raster Before After

RasterDgn's deskew feature works directly on the raster file, not just the view.

You're all done! You just deskewed your raster reference file automatically with RasterDgn. The raster file itself has been deskewed so you'll never need to deskew it again!

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