How do I convert a scanned floor plan PDF to AutoCAD line drawing?

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AutoCAD 2017 and later released has the functionality to easily convert vector based PDFs to AutoCAD line drawings using the built-in AutoCAD PDF Import tools. If you need to read more about this process you can read the following blog: Note the blog was done using AutoCAD 2017 version and since then with later releases of AutoCAD the process has been enhanced whereby you can also convert vector PDF text into AutoCAD text: https://www.mgfx.co.za/blog/building-architectural-design/converting-pdf-vector-lines-into-autocad-lines/

The problem exist when you want to convert a raster PDF drawing to usable AutoCAD lines. These raster PDFs are typically created by scanning a physical paper drawing to a PDF file. This file is in raster format and will not be converted to AutoCAD lines and text using the AutoCAD PDF import tools.

A customer asked a question related to the above whereby he wanted to convert a scanned PDF to a DWG. I am writing this blog to show the process. Note that the process to convert a raster PDF to AutoCAD lines is a manual process unlike the automatic conversion of the vector PDF to AutoCAD conversion.

System Setup

Firstly you’ll also need to install a product called Autodesk Raster Design. Raster Design comes with the old Building Design Suite, new AEC collection and with the new AutoCAD Industry Toolsets. To read more on these products you can visit www.mgfx.co.za and also https://www.mgfx.co.za/contact/ to request a quotation.

Once you have installed Raster Design software it will add an additional Tab inside of AutoCAD as it’s an AutoCAD add in. See below.

Raster Design

You also have a go through an activation process the first time you click on a tool from this Tab. Once everything is set up you can start with the process.

Convert Image

With Raster Design you can attached an image file and then do certain tasks with this raster image including converting it to DWG lines. The issue is that we have a PDF file and not an image file.

To convert our PDF file to an image you can either use Adobe Acrobat software or similar software. The image file format I want to convert the PDF to would be a Tiff file. Tiff files are uncompressed and are one of the best formats to use when edited images.

Searching on Google I found a website to convert a PDF to Tiff for free. The site’s address is: http://pdf2tiff.com/

I uploaded the raster PDF and downloaded the Tiff image file.

Insert Image

Now go to AutoCAD and go to the Raster Design Tab and click ‘Insert’ on the left. Browse to the Tiff file and click Open on the dialogue box.

Insert

Click next on the following dialogue box and noting the Insertion Point equals 0,0,0.

Insert

In the next dialogue keep all defaults and click Next.

Insert

Click Finish.

Insert

The image will be inserted and you might have to ‘Zoom Extents’ to get the whole drawing to show.

Zoom Extents

Now that the raster file is inserted you can start with the process of converting the lines.

Resize Image

You can scale the image if you want now or you can scale the lines at the end of the exercise so that the drawings are 1:1 or real size. Below we’ll scale the image using the Raster Design scale tool. Zoom into a dimension on the drawing and measure it to check. In this case the distance is 1.7574 instead of 3500. See below.

Scale

Then click on the ‘Scale’ icon in the Raster Design toolset.

Scale

The Scale tool will ask for a base point and then to indicate the two ends of the dimension to define the Source distance and thereafter you type 3500 to indicate the Destination distance. See below.

Scale

Now that the drawing is scaled up to real size or 1:1 you can Zoom Extents to see the whole image.

Setup Image

To enable Raster Design to pick up the lines vs the background color the image needs to be ‘bitonal’ which just means black and white. To set the image to bitonal click on the ‘Process Image’ on the Edit Panel and select the ‘Change Picture Depth’ command. Select ‘bitonal’ as option.

Process Image

This will adjust the image to a black and white image. Also as the background is white you need to just ‘Invert’ the image by clicking on the ‘Cleanup’ tool and then ‘Invert’.

Process Image

The background will now be black and the raster lines white. You are now ready to do the conversion.

Convert lines

The process of converting the raster lines to vector lines is a manual process and the tools are in the Vectorize panel. Firstly I’ll show the Primitive conversion using the line tool. See below.

Convert Lines

Once you have selected the line tool it will ask you to select a line. Zoom to a line and select the white part of a line. See below.

Convert Lines

Press enter twice and the raster line is converted to a vector line or AutoCAD line. You can now do this for as many other lines you require.

Convert Lines

Another tool to use is ‘Followers’. You’ll use this tool to convert multiple raster lines into vector lines or AutoCAD polylines.

Convert Lines

Once you select the tool and selected a white line it will give you a preview of the line.

Convert Lines

Pressing Enter twice it will convert the raster line into a vector polyline. See below. Although this is a faster way it might result in some inaccurate converted lines.

Convert Lines

Convert Text

To convert the raster text to AutoCAD text you will select the OCR tool.

OCR

You then select 2 points to indicate the direction of the text.

OCR

Then select the a windows to include the text to convert.

OCR

Once you have selected the text a dialogue box will appear showing the selected text and the converted AutoCAD text. Click Ok.

OCR

You’ll now see the text in the drawing and the raster text is removed.

OCR

There are many other Raster Design tools and you can learn more about these by doing a course through Micrographics or downloading a tutorial here:  http://images.autodesk.com/adsk/files/autocadrasterdesign_10_tutorials.pdf

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