how exactly autocad convert pdf into dwg?

[samifox]

hi

 

how exactly autocad convert pdf into dwg?

 

does it use OCR?

 

tx

[BIGAL]

Optical Character Recognition. Been around for ever.

Edited November 4, 2021 by BIGAL

[SLW210]

OCR is only for the text. The lines they just recreate, since they have to be vector for AutoCAD to convert back. I used to do that with Ghostscript and other programs long ago, then I had a LISP that used Ghostscript, etc. I picked up somewhere. Still need an OCR program for Text from the lines.

 

P.S. PStoEDIT and Ghostscript, the LISP is VECT2PDF

[samifox]

how you can know for sure they use ocr?  if you try to import raster image autocad will ignore it. only pdf with retriveable data can be imported/

[Dahzee]

What is this post really about?

 

Samifox, what do you need to know and what difficulty are you having?

 

Without this information there is no way we can help.

 

Sorry to be blunt.

[samifox]

im writing article about converting option. i couldn’t see any evidence that OCR is part of the algorithm.

[SLW210]

8 hours ago, samifox said:

how you can know for sure they use ocr?  if you try to import raster image autocad will ignore it. only pdf with retriveable data can be imported/

Did you read my post?

 

The only way to convert lines that look like text to text is OCR by definition. That's separate from the Import PDF as AutoCAD Objects. My best WAG is just like I stated...

 

Quote

PStoEDIT and Ghostscript

 

[ammobake]

Regarding PDFIMPORT command...

The sheet that you import from a PDF will get scanned.  As the Autodesk support notes point out...

 

Notes: 

• Lines will become editable geometry and text will become editable text.
• The accuracy of the resultant AutoCAD content is largely dependent upon the quality of the original PDF, so results may vary.
• PDF underlays in drawings created with previous AutoCAD releases can be converted into editable drawing geometry using the PDFIMPORT command. 
• Prior to AutoCAD 2017, it was not possible to convert a PDF file to a DWG file using AutoCAD or AutoCAD LT.
• PDF files could only be inserted as underlays (external references). The content could then be traced and scaled to known dimensions, if desired.
• Using PDFIMPORT with PDFs created from scanned images/documents will result in the creation of a raster image file, which is then attached to the drawing as an xref.
• The raster imagery will not be converted into editable geometry.

Third party PDF to DWG converters can do the job (kind of) but I've seen mixed results.

 

I've used 2 different third party converters over the last 17 years.

They worked for what I was needing but the now built-in PDFIMPORT feature in Autocad works better from my experience.

 

Ideally, you want the PDF to have come directly from Autocad.

The import options have layer settings

Each sheet that is imported will be inserted as a unique Block that can be edited or exploded as you see fit.

 

The process usually works well enough to pull out the data that you are looking to get.

But the feature is not 100%. 

 

Text will normally be imported as "editable" but it sometimes changes the text style and the process does not work with dimensions.  For dims, the text will generally be editable but the rest of each dimension will be imported as linework and/or fills -  such as extension lines and leaders.

 

Also, the feature will break fractions causing you to have to realign every numerator of every dimension.  I'm not sure why but it has to do with Autocad's "PDF Text Recognition"

In addition, Background masks get imported as grey hatches which then have to be fixed manually.

 

So it can be annoying having to deal with.

 

Should be noted as well...

 

If you have a PDF underlay in autocad, you can convert a specific portion of that PDF to DWG objects as well.

This is done in the PDF Underlay contextual tab as "click import as objects".  You are then prompted if you want to delete the rest of the PDF underlay after conversion.

 

There are also other conversion features that are kind of "hidden" in autocad - at least in the sense they aren't readily accessible.

 

If you go into the Autocad PDF Text Recognition settings there are some other options.

For example, you can convert SHX geometry into multiline text objects.

(Click Insert tab, Import panel, Recognition Settings)

 

-ChriS

 

[tombu]

Usually works great as long as you have the correct fonts listed in Text Recognition settings.

Of course even with a listed Text Style like AutoCAD's roamans.shp if it has a width factor or is set to fit width you can have problems converting it.

[SLW210]

I had a very good OCR program that came with a page scanner I bought, this was back when I just bought my 486DX2 computer. It didn't miss a thing. I wish I could remember who made it.

 

Like stated, AutoCAD probably uses the same method that has worked for quiet some time now. Maybe Illustrator and Inkscape use the same method. Inkscape is Open Source and does install Ghostscript and most likely PStoEDIT. Maybe you should dig into those programs as well.