What is Vector Conversion?

Vector conversion or "Vectorising" is the process of taking a raster file (or bitmap) and converting this to a vector (CAD) format. This means your paper drawings can be converted into CAD files.

So, how does a Vector File Conversions Take Place?

Firstly, the drawings are scanned on a large format scanner using lineart scanning. This produces a raster file usually saved in the TIFF format. The TIFF file is then converted, using software, to the vector format.

Several software programs exist with the ability to convert raster files to vector format. They all offer slightly different facilities and are available in a variety of purchase prices. Generally, they are all proficient at converting straightforward drawings containing usual lines, circles, arcs, dimensions, etc.

All programmes have a difficulty in converting text from the raster format into the vector format. After conversion, the CAD file (vector format) normally recognises text as much the same as any drawing entities during conversion. For example, a letter A is not stored as a letter "A" but simply as a series of lines. Because of the complex shapes of text and the many fonts in which text can be written (both by CAD programs and by hand) it is difficult to identify and accurately convert.

Having said this, most of the conversion programmes can be trained to recognise text of the same font and this is of use where there are large numbers of drawings using an identical font e.g. stencilled text of the same size or that produced by CAD drawings. However, for practical processes text does convert easily and is stored as a series of lines and arcs after conversion. Nevertheless, it still appears similar to the original text on the drawing.

Due to this, text may require editing after conversion and may need to be re-entered as actual CAD text characters if this is required.

What Happens to Dots and Smudges?

During initial scanning, the "de-speckle" facility will remove some dots etc but not always all. A level has to be struck above which the program is instructed to ignore dots, as they may be data. If the image has been scanned in Greyscale at 8 bit, there will be 256 levels of grey. It is possible to delete some grey levels e.g. "smudges" and then convert back to "lineart" i.e. one bit depth as black or white. However, for "clean" drawings this is not necessary.

Once smudges and speckles have been removed at the raster stage, conversion to vector format takes place. Everything the conversion program recognises as on entity is converted. Hence, "dirty" drawings may have many small lines or dots and squiggles that have been translated from original dots and smudges. These can simply be "windowed" in the CAD package and deleted to remove them.

Post "vectorisation" cleaning by the operator is not normally included within the conversion price as its requirement is subjective and the extent to which it may be taken always difficult to define. Good quality drawings require little cleaning, if any. Hdi can provide manual cleaning of drawings if required.

What's the Advantage of Vector Conversion?

The advantage is the low cost and speed of producing a CAD file from a paper drawing. Manual CAD re-drawing may take a draughtsman several hours to produce a CAD drawing by slowly re-drawing from the original paper drawing. However, if the cost is acceptable, this will produce a cleaner drawing than software conversion.

Can any Drawing be Converted?

A reasonable quality, i.e. relatively clean print or drawing is required. Drawings that are very intense, e.g. electrical schematics, poor quality drawings or similar, may not convert successfully. If in doubt regarding the quality of your drawing, we will advise before proceeding.

Drawings would be scanned at 400 dpi in mono and then converted to a DXF or DWG file maintaining the original scale. As part of the conversion, de-speckle, de-skew and cropping are normally provided carried out.

Can my Existing Raster Files be Converted?

If the drawing was a clean drawing and the scanned file is a reasonable image, then yes they can be converted.

Usually, the scan is at 200 ppi and this is preferentially increased to 400 ppi to improve image quality. Why not send us a sample by email and we would be pleased to advise you.

Is Raster to Vector Conversion Expensive?

Individual files can be converted for around under £25:00/drawing and this price will reduce substantially to a few pounds with quantity.

Will my CAD Package View Raster Files?

Yes, the raster files can be viewed in various CAD packages e.g. in AutoCAD. In fact AutoCAD can call up a raster image ("Insert" then select "Raster Image"), and permit the user to overdraw in vector format and then save the raster/vector hybrid drawing in DWG or DXF format. Alternatively, the raster image can be subsequently deleted leaving only the vector drawing.