This is also known as “classifying” a raster and involves generating a polygon for each contiguous area of pixels with similar values. Extract polygons from a raster based on pixel values Learn more about converting imagery into usable data in our blog about extracting geospatial data from PDFs. The text shown in the PNG image on the left has been extracted using the TesseractCaller. Preparing the output involves smoothing the polygons generated by Potrace so we end up with nice blocky shapes instead of crazy 1000-sided chiliagons. Preparing the raster therefore involves classifying color ranges so the number of colors is reduced - extracting the dark shade representing buildings and leaving everything else as the background. In the image, buildings are shown in a darker shade. In the below example, the user has an RGB image of an area and needs to extract CAD polygons of buildings. Converting raster to vector in this context involves three steps: In FME, you can leverage it via the custom transformer PotraceCaller. Potrace is a free tool for turning bitmaps into vector graphics. Trace an image to convert it to CAD or GIS Here are three ways you can do it by processing your raster in an FME data integration workflow. There are many possible ways to tackle these problems, some easier than others, some more accurate. Maybe you’d like to digitize a scanned map, convert a DEM to polygons based on elevation, extract text from an image, or otherwise generate polygons from a supplied image. This is a common scenario for GIS and CAD workflows, and a challenging one. In my testing the drawing used, created a 167kb vector file, using Hidden and settings the PDF Options to 350x350 dpi, gave a readable 400kb raster PDF that cannot be converted.Extracting vector features from an image (or “vectorizing a raster”) involves converting groups of raster pixels into polygons. With a bit testing, you can balance quality and file size to something acceptable. If you then want to manually tweak the quality/file size further, you can edit the PDF Options below: For example a drawing that makes a 150kb vector PDF file, will make around a 1mb raster PDF file.Ī quick way to decrease the file size, is to set the Quality to Preview: You will notice however the file size is a lot larger than a vector PDF. In the Plot setup go to “Shaded viewport options” and just change this from the default “As displayed” to Hidden, Realistic or Shaded: To do this inside of AutoCAD use the following settings. If PDF is needed, then we need to create a raster based PDF file which cannot be converted. If we are not worried about format we could use Autodesk’s DWF format instead, this is generally smaller in file size that PDF and can be viewed easily in many ways. However what if you do want your design to be used or converted in AutoCAD 2017? The design could be protected in some way, or maybe you do not want to give your design to someone who may change it. My colleague Clint Brown produced the following article on this: This can be very useful when sharing designs between departments or even businesses. With the Introduction of AutoCAD 2017 came the excellent feature to import and convert vector based PDF files into AutoCAD geometry.
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