By Martin Phelps
To keep records of manually produced drawings, that’s drawing produced with a pen or pencil on paper; the old way prior to CAD programs, many companies in all areas of industry have scanned their old drawings into a digital format, this saves space – no plan chests cluttering up the design office, and it also enables the images to be sent across the internet – no waiting for a paper copy to be sent via post. This is not its only application since more and more digital data is becoming readily available.
For a long time now, AutoCAD has had the ability to add a digital photographs or raster images to a drawing, but its functionality has been very limited with the user only being able to only either clip the image via rectangular or polygonal shapes, or change the brightness, contrast or fade properties of the inserted raster image.
Raster editing software is not new, and it’s not new to Autodesk, it’s not even new to the suite offerings but it does get overlooked.
The Raster Design product is available with most suites, and is an ideal tool for making changes to scanned drawings and images, such as adding and cleaning up data without the time consuming process of redrawing.
Raster Design not only allows you to effectively use scanned paper drawings, but also aerial photographs, Digital Elevation Models (DEM) and satellite data inside your AutoCAD drawings. Bitonal, greyscale and colour raster images can be inserted in to the drawing files these can be edited, analysed and the results exported.
Depending on the way the original file was scanned and how much care was taken in the scanning process this may well have an influence on the final raster file. A paper drawing may have areas that are not relevant to the drawing detail such as finger marks, pencil smudges, stray pen or pencil marks, or even tea or coffee cup stains, the drawing may also have been scanned at an angle, or even end up a mirror image of the original, and if the drawing has been produced on trace sheet it may have become distorted over the years. Drawings on trace sheet are susceptible to damp, hence the distortion.
These issues can be resolved by using the “CLEANUP” and “RUBBERSHEET” tools with in Raster Design.
For example if the image is not aligned with the horizontal, it may be adjusted by using the “DESKEW" tool.
Unwanted Raster may be removed be either deleting the unrequired raster or setting a speckle size with in the “DESPECKLE” tool.
If the image has been reversed during the scanning process, then the “MIRROR” tool can put the image back to its correct state.
These are just three of the many tools with in Raster Design, as well as the ability to clean up raster images, Raster Design can also convert or vectorise raster to vector; this function can be used in conjunction with the “RASTER SNAPS” to increase accuracy and speed of this process. The text recognition tools allow the conversion of scanned text into either AutoCAD “MULTILINE” OR “SINGLE LINE” text. Created vectors can be converted back in to raster, removing the need for a file to contain both raster and vector data.