In the Tailor Made Software conversion, data-extraction and data-manipulation engines, we map the Entities between DWG and PDF the following way:

Entity Mapping from DWG to PDF

An AutoCAD Drawing file (DWG) has a much more complex file format than an Adobe Portable Document Format (PDF) file. PDF files have a very limited set of entities: paths (essentially moveto, curveto and lineto operators), text and images.

The only “grouping” type element in PDF is the Optional Content Group which is usually used to emulate layers.

Any “higher order” AutoCAD entities, such as dimensions, leaders, faces and, of course, blocks, have to be devolved into many, now unrelated, seperate PDF operators.

AutoCad Entity       Description       Relationship       PDF types
line two point line 1:1 path
polyline multiple point line, can have “bulges” (arcs) 1:1 path
point point 1:1 path
xline infinite line from point in two directions 1:1 path 1)
ellipse ellipse 1:1 path 2)
shape Elements from an AutoCAD shape file 1:many various
polygon closed polyline 1:1 path
face 3D face 1:many path
arc circular arc 1:1 path 2)
solid 3 or 4 coordinate solid 1:1 path
ray infinite line from point in one direction 1:1 path*
text text 1:1 text
spline various forms of splines 1:1 path 2)
MText multi-line text 1:1 text
MLine two or more parallel lines 1:many path
insert block reference 1:many various
leader leader lines 1:many path and text
hatch Filled areas with polygons and donuts 1:many paths
mpolygon Filled areas with polygons and donuts 1:many paths
surface Boundary meshes 1:many paths
solid3d 3D Solids 1:many paths
attribute text information associated with block 1:1 text
MLeader Multiple leader lines 1:many paths
Image Raster Image 1:1 Image 3)

Note:1) PDF cannot represent an infinite entity where the line keeps going in one or both directions. As a result the XLine and Ray can only be approximate to the edge of the drawing.

Note:2) PDF uses Bezier Splines for curve definition, while AutoCAD can use circles, circular arcs, ellipses, and various forms of splines (not including the Bezier Spline), so any conversion to PDF’s Bezier Spline is approximate.

Note:3) PDF only supports JPEG and PNG images so Image may need to be converted

Entity Mapping from PDF to DWG

Since PDF has a limited set of entity types compared to DWG, a round-trip conversion (DWG->PDF->DWG) would differ greatly from the original DWG.

PDF Type       Description       Relationship      DWG Type
Path MoveTo, DrawTo 1:1 Line, Polyline, Polygon
Path MoveTo, CurveTo (Bezier segment) 1:1 Circle, Arc, Ellipse, Spline 1)
Path MoveTo, LineTo, CurveTo 1:Many Polyline, Arc and/or Spline 1)
Text Text 1:1 Text
Image Raster Image 1:1 Image

Note:1) What sort of entity can be used is determined by the mathmatics of the Bezier Spline (CurveTo) operators in the PDF file and the tolerances allowed. For instance, any Bezier Spline can be approximated by a series of arcs, but it may require A LOT of arcs to do it, depending on the curve and the tolerance. However, for a very large tolerance it is possible to fit a linear polyline. It will not look as good as the series of arcs, but mathmatically it will be correct. So a series of CurveTo operators may end up as a circle, an arc, an ellipse, a series of arcs and line (or a polyline with bulges), or even a spline.

Please Contact us for your specific platform, encapsulation and format requirements, and we’ll build it for you!