DXF (Drawing eXchange Format) is the vector file format developed and maintained by Autodesk for the exchange of 2D/3D CAD data in an AutoCAD drawing with other applications. It has been adopted as an industry standard for this purpose, with widespread support for reading and writing DXF files across CAD/CAM/CAE and other technical applications (such as CNC machines).
DXF files generated by Visual integrity software can be imported and edited in AutoCAD and other packages such as Microstation, UniGraphics and PowerShape. An SDK is available for developers and OEMs to create plug-ins or add direct pdf2cad functionality to their applications.
Frequently Asked Questions
There are two types of PDF files – raster PDF and vector PDF. If your drawing will not convert, it is probably a scanned drawing saved as a raster PDF file. Unfortunately, there is no useful data in a raster PDF file for us to extract about the objects or text. When a drawing is scanned, it is reduced to a flat image, comparable to a snapshot or a photocopy. There’s nothing you can do except trace over it manually or with tracing software (raster-to-vector software). One way or another, you need to recreate it.
Our software is designed to convert vector PDF files. These files are created on computers using save, export, print-to-file, etc. These vector PDF files contain a rich data set and all the information we need to accurately extract the drawing and render it in a format Visio or AutoCAD, etc can digest.
For comparison sake, below is a snip of a raster PDF file at 500% where the characteristic “jagginess” or pixelation of raster PDF files can easily be seen. Below it is a snip of a vector PDF file which is remarkably smooth and clear even though it has also been zoomed to 500%. This visual method is a very easy and accurate way to determine if your PDF file is a raster or vector. Most people get both types of files so pdf2cad or pdf2picture may be useful for some of your files.
A sample vector PDF file at 500% – notice how smooth the lines are and how clear the text is. This type of file is best converted with vector-to-vector software like pdf2cad and pdf2picture.
When a CAD drawing is saved as a PDF file, it still retains information about layers that can be extracted. When converting, pdf2cad looks at color attributes, or other definitions in the PDF file, to create layers. If the option to recognize layers is turned on, pdf2cad gathers all objects with same color and put them on one layer. If the PDF file has three colors, the resulting DXF file will have three layers. It is then easy in AutoCAD to turn off a complete layer. This setting can be found in the Options->DXF tab of PDF FLY or simply under Options in pdf2cad.
There are two basic formats for graphics – vector and image. Vector graphics are made up of objects, lines, curves and text while images are made up of a collection of dots or pixels. Images are also referred to as bitmaps or rasters.
Visual Integrity can convert most PDF files into either vector or image formats. It’s important to know which is best for the job you are doing.
If you need to break a PDF file down into objects and text for editing, then you want to choose a vector format. The vector formats supported in our software are DXF, PDF, PS, EPS, SVG, WMF, EMF, CGM, HPGL and MIF.
If you do not need to edit the file and simply want a sharp copy to insert into a document or to publish on a web-site, you’ll want to go with image formats. The image formats that we support are TIFF, GIF, PNG, JPEG and BMP. If you will be printing the graphic on a laser or ink-jet printer, convert at 150 or 300 dpi (dots per inch) resolution. If publishing to a web-site, use 96 or 72 dpi is best for screen display. Keep in mind that the higher the dpi (resolution), the larger the file size. It’s best to use the lowest resolution which achieves the level of quality you want.
Note! Scanned images can not be transformed by vector mode into lines, text and other vector objects because they are not vector source files. Instead, you will get an exact replica of the PDF as an image that can be used as a tracing layer which aids in the duplication effort. To convert scanned images into vector objects, you need a special class of software called “raster to vector”.
The DXF file format does not define physical dimensions using absolute measurements from a ruler. Instead it uses units which the user defines. When you create a PDF file from a CAD drawing, it is transformed to paper/print dimensions and the meaning of the original CAD units are lost but the xy relationship remains. As a result, pdf2cad can not restore the intended dimensions but it does preserve the scale. This means that you can calculate a scaling factor to apply during the conversion to achieve the size drawing you want. By default, pdf2cad uses 1mm(0,03937 inch) in the PDF = 1 unit in the DXF. You can change this under the DXF Options tab. You can also scale the DXF after import into your CAD application.
Tip: Sometimes pdf2cad delivers better precision and more accurate coordinates if you change one of the values in your pdf2cad.ini file. Please try setting the ctm_scale to 10.0 instead of 1.0 (default) in the pdf2cad.ini file. If this does not help, please send us the file to diagnose.
If the PDF file contains characters, pdf2cad will convert them and map them as MTEXT objects in the DXF file. Unfortunately, when creating a PDF file from a CAD drawing, the text is not always retained. Sometimes it is “plotted” as pen strokes or turned into curves. When this happens, the character definition is lost. There is nothing that pdf2cad can do about this – it can only reproduce the curves (=SPLINES entities) in the DXF file. What looks like text in the original file may actually just be an object, comprised of a series of pen strokes that looks like a letter.
Tip: to see if the text in your PDF drawing is live and searchable, open the PDF file in Acrobat (Reader) and use the Text Select tool. If you cannot highlight any words, the text is already outlined to curves. If a PDF file contains searchable text, pdf2cad will reproduce it as MTEXT in the DXF file, preserving the fonts and styles.
Tip: To create a PDF with searchable text from AutoCAD, make sure to use TrueType fonts in the drawing and ensure that your printer driver is set to retain text as text instead of converting it to curves. Text can be lost in either of these two steps in creating a PDF file. See how to create a PDF file with searchable text from CAD Digest.
Tip: if your PDF files contain non-Roman font text (such as Chinese, Arabic or Cyrillic), or if the text looks garbled in the DXF output, try using the “Convert characters to curves” option in the General tab of the Options menu of pdf2cad. This outlines the text during conversion to ensure WYSIWYG rendering (not editable).
When you see a width dimension or what look like very fat lines in the drawing, you need to adjust the line width setting. It’s possible to turn off (reduce to zero) the line weight on the DXF Options tab or via Command Line. Change the value of the function zero_linewidth from 0 to 1 in the pdf2cad.ini, which is in the installation directory of pdf2cad and rerun the conversion. The installation directoryby default is C:Program FilesVisual Integritypdf2cad.
When the PDF file was created, the dashed lines were created as small individual line segments. Because of this attribute in the PDF file, pdf2cad converts them as small line segments in the DXF file. pdf2cad does not yet have an option to recognize these segments. as a line with a certain dashed-line attribute.