Common DWG Conversion Problems

Updated Jun 28, 2018
DWG Conversion Problems

With its rich features and status as the native file format for AutoCAD, it’s easy to see why many designers want to convert to DWG. Whilst conversion is a complex process, that doesn’t mean that it has to be difficult. Scan2CAD makes the process easy – we’ve even created a simple conversion guide for users to follow.

Nevertheless, it’s still all too common to run into problems with converted DWG files. We’ve put together a list of some of the most common issues users face, as well as the solutions you need to tackle them.

Converting from JPEG or GIF

One of the advantages of using Scan2CAD is its support for a large number of file types, allowing you to convert a number of raster image file types and PDFs to DWG. However, whilst it is possible to convert to DWG from all major raster formats, some are more suited to vectorization than others. We would advise users to avoid using poor quality JPEG and GIF images when converting to DWG.

JPEGs are a popular format for photography, and come with small file sizes. However, this comes with a trade-off. JPEG uses lossy compression, which means that any time you edit a JPEG, it loses quality. The lines in a JPEG file may therefore become pixelated and lose definition.
Learn more about JPEG to DWG conversion by checking out our ultimate guide.

GIF, meanwhile, uses lossless compression. This means that it can be edited without losing quality. Nevertheless, some GIF images can still be unsuitable for vectorization. This is because GIFs are usually of low resolution. A GIF file is meant to support 256 colors; to increase this number, techniques such as dithering may be used. This can make GIFs look fuzzy and undefined.

The ideal image for use in vectorization is clean, well-defined, and contains few colors. Scan2CAD recommends saving your image file as a TIFF, as this allows you to compress your image without any loss in quality. Another suitable choice for vectorization is the more popular image format PNG.

Poor raster image quality

So, you’ve saved your raster image as a TIFF or PNG. Is it ready for vectorization now? Not quite. Even if you’ve used the correct format for your raster image, it might still not be ready for conversion. Raster images will often have imperfections, such as speckles, holes, and ‘hairy’ lines, especially if they have been scanned in.

Poor image quality for raster to vector conversion

Some of the most common problems with raster images

Vectorization works by detecting lines and patterns within your image. To be able to get precise vectors, your image needs to be as clean and simple as possible. Ideally, your raster image should have clean, unbroken lines and few colors. This is why architectural and engineering drawings are best suited for vectorization, whilst photos work less well.

No matter what type of raster image you’re starting off with, there are always steps you can take to improve your chances of good vectorization results. Even if your image looks vector-ready on first glance, make sure you follow our Raster Quality Checklist. This handy guide covers the steps you can take to get your image ready for vectorization.

For even more useful tips, you can also check out top ten raster effects to optimise your vector conversion.

Incorrectly-recognized text

As noted, vectorization works by tracing over patterns in a raster image. Whilst this process works well when it comes to lines and shapes, it can struggle to deal with text. Without the proper tools to handle text, an O could become a vector circle and an L would be a right angle. Not only does this look wrong on the page, it also makes it extremely hard to edit.

Good conversion software, meanwhile, has an important weapon in its arsenal to deal with text: Optical Character Recognition, or OCR. Working from a database of patterns, OCR is able to detect characters and create editable text strings. Scan2CAD comes with OCR built in — making the conversion process easier. Its powerful technology mean that text is rendered correctly and assembled into logical text strings.

OCR text conversion using Scan2CAD (left) and other software (right)

The text on the left was converted using Scan2CAD. The text on the right was converted using a different CAD program, and hasn’t been correctly reassembled into strings.

Common issues with text conversion

Despite Scan2CAD’s powerful OCR technology, problems still arise when dealing with text. Some of the most common can be solved by following our Raster Text Quality Checklist. We’ve listed some common issues (and their solutions) below:

  • Your software can’t recognise the font. Whilst OCR is able to recognise characters across a range of fonts, it’s not 100% foolproof. Sometimes fonts are too far outside of the standard patterns to recognise. To fix this, you can train Scan2CAD to recognise new fonts. Learn more about font training at our user manual.
  • The text is handwritten. As there are no regular, predictable patterns to handwritten text, it is very hard for OCR to deal with it. If possible, the best solution may be to simply type over it with new vector text. This solution can also apply to other types of illegible text.
  • The text is written over other drawing elements. In this case, it is impossible to separate out overlapping elements. The only way to fix this is to use a different raster image.
  • The characters are too close together. If different characters touch, then OCR will find it hard to separate them. To fix this, try selecting OCRSettingsSplit before starting OCR.

Unable to open DWG file

So, you’ve converted your file to DWG, you’ve fired up your CAD software, and… you can’t open your DWG file. Why is this happening? The two most likely reasons are that you’re using the wrong DWG version or that your software doesn’t support DWG. How can you fix this? Read on…

Wrong DWG version

Like many common file formats, DWG is subject to software versioning. Every few years, as CAD software evolves, new features are added to DWG. The current DWG format is therefore much more complex than the original DWG files of 1982. As a rule of thumb, new software can still support old versions of DWG, but old software can’t support new versions.

Before you convert, make sure you’re aware of which versions are supported by your CAD software. In many cases, the only thing you’ll have to do to solve this issue is to open up your file in Scan2CAD and save as a different DWG version.

Software doesn’t support DWG

Maybe the problem isn’t that you’re using the wrong version of DWG—maybe your software just doesn’t support DWG at all. The DWG format was built to work specifically with the CAD market leader, AutoCAD. It is a proprietary file format, which means that developers must have a licence to use the format in their software. As a result, many CAD programs don’t support DWG. So what should you do if you don’t have AutoCAD?

One potential solution is to simply convert your DWG file to DXFDXF is another CAD format, and unlike DWG, it is an open standard, meaning that it is supported by practically every CAD program. However, it lacks some of the functionality of DWG files, with some AutoCAD-specific vector elements being unsupported by the format.

Luckily, there are alternatives which will allow you to view and edit your DWG files without AutoCAD. Autodesk also produce the browser-based A360 Viewer, the desktop software DWG True View, and the cloud-based app AutoCAD 360. Outside of the Autodesk family, there are many other programs which can be used to view DWG files—amongst which is our very own Scan2CAD.

Convert to and from DWG, DXF, and dozens of other file types with Scan2CAD. Try out our fully-featured 14-day free trial.

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