What's the difference between raster and vector files?

A raster image is roughly equivalent to a newspaper photograph. If you look closely you see that it is made up of lots of small dots. The density of these dots is referred to by resolution, measured in dots per inch (stated as 'dpi'). Raster files are stored in many file formats. TIFF is a common example.  Vectors are used to describe specific objects defining their size, position and geometry. The image seen on screen in a CAD application is only a visual representation of the vector file. The vector information in a CAD file is mathematical. It is not stored as an image.  So, for example, a vector line is an absolute line connecting two or more points; a vector curve is described by source coordinates, a polynomial equation and end point coordinates.  Vector information is stored in many different file formats, one of which is DXF. The primary function of the DXF file is to permit CAD vector information to be exchanged between different CAD applications.

Do scans work in a CAD program?

Scanners produce raster images, not the vectors used in CAD programs. When CAD software allows import of a raster, it will display it as a raster (i.e. dot based) image within the CAD document.
The lines in a raster image in a CAD document cannot be manipulated in the CAD program. The CAD program will not convert it to vectors unless assisted by a conversion program like TracTrix.

How can I use my desktop scanner to create CAD files?

Paper to CAD (raster to vector) software such as TracTrix take your scans, convert them to vectors and output them as a DWG, DXF, IGES, HPGL or other vector file format. In the case of TracTrix this can be done within AutoCAD itself or outside of AutoCAD.

What's the difference between pixels and dots per inch? Is a dot a pixel?

A pixel is a minute circular point of light about 10 or 12 thousandths of an inch in diameter (sometimes stated as 10 or 12 'mils') created on a monitor screen.  A dot is a sample taken by a scanner for representation in a raster image. A 300 dots per inch (dpi) scan takes snapshots of dots which are about 3 mils across (3,33333....mils to be exact).   To represent a 300 dpi scan on screen at a 1:1 scale your computer typically has to consolidate groups of 16 dots (each 3.33... mils diameter) into a single pixel (10 - 12 mils diameter)  This means that the raster image you see on screen is only an approximation of the underlying digital 'dpi' information from your scan. And your scan itself is an approximation. Sometimes the screen appearance can be disconcerting.

Why can't I just edit my raster files and not have to bother taking them to vector?

Raster files are excellent for visual purposes, for Web posting and distribution, for archiving and for security in release control (see Trix RasterServer) - after all they are a picture of the original image just like a print. TracTrix does provide raster editing tools so you can edit and clean up your scans. But raster editing can be tedious if there are considerable modifications to be done - especially if you are used to the power of a CAD package.  And all CAD software uses vector objects instead of rasters. The primary benefits are ability to precisely describe, create, scale and manipulate individual objects.

In image resolution, what's the difference between 400 dpi true and 400 dpi interpolated?

True resolution is the number of dots per inch of reflected light captured by the scanner head. The scanner head is physically limited in the number of dots which it can capture.  Interpolation software (usually built in to the scanner, but also available in raster manipulation programs) can make a good guess at what lies between the dots recorded by the scanner.
By comparing adjacent dots captured in a true 200 dpi scan interpolation software might replace each dot with four new ones (creating a 400 dpi interpolation) or even nine new ones (creating a 600 dpi interpolation).  For many applications (including the majority of paper to CAD conversions) interpolation works well. But interpolation will never be as accurate as a true resolution.

Is there an international standard for vectorization?

No. But conversion of paper to CAD and indexed raster images may provide you and your organization with an excellent opportunity to begin implementing ISO 9000 quality standards.
A good engineering document management system goes a long way towards meeting the ISO standard. 

I've too many drawings to vectorize in-house. How should I choose a conversion bureau?

There is a pretty clear relationship between price and quality in bureau conversion. We recommend starting with a pilot project comprising two stages. In the first stage establish that the bureau can deliver to your required quality for a small sample of drawings, say five or ten.
From this limited experiment set the parameters for a second stage test with a much larger sample of your drawings (maybe 5% of your stock). The second stage determines how your bureau will perform under a real load.
You and your bureau can establish a solid relationship during this test and sort out potential problems. And most important, involve your eventual users in the test. Have them check that the quality meets their needs. Some users may need help in defining their needs. You might want to think about an alternative to vectorizing all of your drawings. That is to scan all of your drawings and vectorize later as required. 

If I have a small or hand-held scanner, can I scan a big drawing in pieces and 'stitch' them together afterwards?

If you have access to a large format scanner use it instead of stitching small images together. TracTrix can convert very large drawings (E/A0 and above). Many areas have copy shops or similar reproduction shops where a large document can be scanned to disk without editing at very reasonable prices.  For instance a busy 'A0' size drawing scanned at 300 dpi monochrome (black and white) can be stored on a 3 1/2" diskette or emailed to you from your scanning bureau. The raster file on disk can then be vectorized in TracTrix at your convenience. Do be sure that your bureaus understands the level of quality and resolution you require before they scan the drawings. Vector output is only as good as the raster input. Advice on how to scan for best results is included in TracTrix manuals.

What should I be aware of before I start converting images to CAD?

Vectorizing packages do not add information to your original drawing. We tend to think of drawings as being super accurate. This is not true. An image on paper is imperfect, inaccurate and imprecise. This may seem like a heresy to all who (like us) have slaved over drawing boards. Think about what we do when we 'read' a drawing:
Our intellect works wonders piecing together the disparate pieces of information which our eyes pick up from a drawing; Our brain automatically sorts text from line work and combines different sorts of visible information into a comprehensive whole. With this we can mill our piece, set our forms, etc. to the designer's requirement.
Contrast this with CAD. When we work in a CAD package vector information is created. The dimensions are the primary information and the CAD package produces a visible representation on screen (or to a plotter) based on these dimensions. This output is an approximation from the absolute dimensions of CAD. We go through the same processes to begin milling or setting up our formwork. And whether the information began in CAD or on a drawing board, we adjust it to the accuracy needs and limitations of the real physical world.

What are my options when considering how to get from paper to CAD?

There are several methods that will help you take a paper drawing or print into CAD. You could simply redraw from scratch in a CAD program, you could create a vector file from the drawing on a digitizing tablet, you could scan the drawing, open it in a 'Head-up' digitizing program on your monitor and digitize to vectors with a mouse much like the digitizing tablet or you can use an automatic raster-to-vector program like TracTrix.
Tablet and head-up digitizing is subject to the skill and eye-hand coordination of the operator. Studies have shown that as digitizing operators tend to wander off the original lines by as much as 1/32 of an inch as they progress through a days work. Automatic raster-to-vector conversion will provide you with editable vectors in a fraction of the time of other methods.

So what's the process involved in translating paper to CAD?

It always requires two stages. In the first you scan and convert a raster image of the original drawing to CAD vectors . In the second, you check that the CAD representation created by vectorizing meets your need for accuracy and purpose.
You've probably heard the expression "garbage in, garbage out". This is not more true than scanning a paper drawing and vectorizing it. Vectorizing software can only make vectors where there is raster information for it to track.
Breaks in the lines, poorly connected lines at corners, blobs in the image at multiple line intersections and similar imperfections in the raster image all contribute to imperfect vectors.
TracTrix is used by a major prosthetics manufacturer to create cutting and drilling templates for microsurgery. Their originals are very finely detailed. Generally, the accuracy you'll achieve will depend primarily on the quality of the original drawing. Accuracy can then be made absolute in whatever CAD software you are using.
You should always expect to take raster images automatically to vectors and then edit them to the precision your application requires.

What else should I be aware of when considering paper to CAD conversion?

Manipulating large image files is best done with plenty of RAM. For example, a 300 dpi scan of an A3 size drawing will create an uncompressed file that is nearly 17 Megabytes. RAM therefore is an important consideration when converting and manipulating image files. At least 32 or even better 64 meg of RAM is recommended for paper to CAD conversion.

How about drawings that have been reduced to a smaller size?

When large drawings are reduced to a smaller size (using the 'reduce' function on a scanner or copier) lines and details tend to bleed together into indiscernible blobs of pixels. Parallel lines that are close together blend into one line. Small holes in the original drawing close up to a solid black object. TracTrix cannot 'read' through these solid black objects to figure out what they are. Therefore we do not recommend reduced size drawings as a starting point for automatic raster-to-vector conversion.

What is the difference between accuracy and precision in vectorizing

Repeating the point above: Scanning paper to create a raster image does not improve the quality in any way. As a matter of fact the scan is a less perfect than the original. Vectorizing software of any type can only vectorize that which it can 'see', the pixels in the raster image. The resultant vectors are no more perfect than the raster.
Vectorizing is accurate to the extent that the vectors are an accurate representation of the raster image. Is this 'accuracy' good enough for your application? Perhaps. But if it isn't, the vectors can be edited to make the vector file as precise as you require. Remember, vectors can be made to be mathematically perfect, rasters cannot.

Does high resolution (dpi) assure vector accuracy?

TracTrix follows either the centerline on lines or the outline of images. It achieves this by looking for pixels. In centerline tracking, TracTrix looks for the chosen line width by looking at pixel quantities across line and seeks the mean center of the line. Having more pixels from a higher resolution will not necessarily create a "better" mean centerline.
When following an outline it looks for pixels on the edge of the image. Higher resolution might present a 'smoother' less jagged edge for TracTrix to vectorize but the vectors are not more accurately created. Higher resolution makes for bigger files to manipulate. Bigger files require more pre-processing storage and processing takes much longer (twice the resolution means four times as many pixels to store and process).
As a general rule, there are rapidly diminishing returns from increasing resolution for raster to vector conversion. We tend to use 300 dpi or 400 dpi. Occasionally we need 600 dpi for small, finely detailed, originals.

Horizontal and vertical vector lines on screen do not appear to be straight, but they were in the original drawing. Why?

What you see on screen is only a visual display of the actual stored CAD file and does not represent what the file will create on a plotter or printer. The vector points, also seen on screen, more accurately depict the vectors as they will be plotted. What you are seeing is the result of a slightly askew scan.
When a computer depicts straight lines on screen they will appear straight, without a jagged appearance, only when they are absolutely square to the screen's matrix. That is if they are perfectly parallel to or at right angles to the horizontal scan of the monitor.  If they are slightly off square the computer tells the screen to depict the straight line as a Cathode Ray Tube scan series which might be: Fill 100 pixels horizontally, go down 1 pixel, fill 100 pixels horizontally, etc.  It is this small one or two pixel step down which makes straight lines appear to have a jog or appear jagged on screen. The underlying vector which it is representing is a single point-to-point line.
Consider the jogs to be an optical aberration on the monitor screen and not representative of the actual vector. In TracTrix, one can see the actual vector points at each end of the line by clicking on the line.

How come some vector files are bigger than raster files of the same image?

The raster image size is based upon the resolution (dpi) and the physical size of the image. The vector file size is based upon the number of vector entities required to represent the raster file. The relationship between the two varies with the content of the drawings, the entity types in the vector file, the raster format used and whether there is compression in the raster format.

My drawings are already in CAD. How do I publish them electronically around my company?

After more than a decade of building engineering document management systems it is clear to us that raster file formats are the most secure, tamper-proof, durable and easiest method for publishing and archiving CAD designs. For some of the reasons take a look at our RasterServer page.
In brief: Raster formats such as TIFF, CALS and C4 are non-proprietary, stable - you won't have to buy 'upgrades' every couple of years, and viewable and printable from a wide variety of viewing software.

How can I publish engineering drawings on the Internet?

The simplest method is to rasterize completed CAD designs from DWG or DXF to a raster format that can be viewed by a Web Browser. These formats are PNG, JPEG or GIF. These can be published using the regular IMG tag in HTML. TracTrix and Trix RasterServer produce the PNG format for this purpose. The user needs nothing more than a recent Web Browsing software.
If you have large, complex, files and/or you want to do more than just view a drawing through a Browser you should look at adding a viewer plug-in to the users' Browsers. Plug-ins add functionality to a Browser. For example, Trix Systems offers a Plug-in version of Trix DrawingCenter. When this is installed a user can view DXF. DWG, HPGL and many raster file formats. The publisher does not have to convert these to PNG, JPEG or GIF. In addition to viewing the plug-in provides annotation, measuring tools, printing and saving controls. The user can add additional information to a copy of drawing and save it at the local workstation.
Other companies also offer plug-in viewers. There is an AutoCAD specific DWF format which also requires a plug-in. The PDF format is also for Web publishing using Acrobat Reader as the plug-in for Browsers. TracTrix and Trix RasterServer also convert CAD formats to PDF files.

What is the typical TracTrix Paper to CAD conversion process?

Scan your original into TracTrix. Select the description which fits your type of drawing from pre-defined types (e.g. architectural, contour, illustration, logo, mechanical). Select the portion of the drawing to convert. TracTrix then automatically processes the raster lines into vectors. Compare the vectors with the underlying original raster image and make any post-processing changes using TracTrix' built-in vector editing tools. Export the result in the vector format of your choice.

Speed/Expectations

TracTrix typically can convert a busy E-sized drawing in about 2 minutes on a Pentium 400MHz machine.
In our years of providing image conversion for customers we have learned that individual needs are unique. So we are reluctant to suggest exactly what savings TracTrix can bring you. But based on the tens of thousands of drawings that we've converted in our own conversion bureau, we'd hazard a guess that after building in post-processing clean-up you could aim for 50% savings in hours spent on conversion.  That's not to say that all drawings lend themselves to raster-to-vector conversion. Depending on quality and intended application, you'll find some drawings can be almost entirely vectorized using TracTrix, others may inevitably require manual redrawing.
TracTrix is very forgiving in that the vectors created can be deleted and re-vectorized, edited and all vector errors corrected before saving in the CAD file format of your choice.

Will TracTrix give me a DWG file?

Yes.
TracTrix software also generates DXF, IGES and other vector description files which import into virtually all CAD packages. After you have imported the DXF, or IGES file into your CAD package you have a CAD document on your screen. When you open and save this from within whatever CAD program you have it creates the native CAD file for your CAD package.

Do I have to use TracTrix to drive my scanner, or will any image file work?

TracTrix can start with a raster image file from many different sources. Your, or your vendor's or your bureau's scanner(s) will produce a raster image file which TracTrix can work with. Digital cameras, scans from aperture cards and film are all raster files that TracTrix can convert. TracTrix also includes a TWAIN driver and large format scanner drivers to directly scan images into TracTrix.

What raster and vector formats does TracTrix work with?

Depending on version of TracTrix used, TracTrix can import
ATT, BMP, BRK, CALS-Group 4 Type 1, CALS-Group 4 Type 2, CLP, CUT, DCX, DIB, GEM IMG, GX2, GTX G3, GTX G4, ICA, ICO, IFF, JEDMICS C4, JPEG, KFX, LV, PCX, MAC, MSP, PCD-Photo CD, PICT, PCX, PSD-Photoshop, RAS, TGA, TIFF- Pack Bits, TIFF-Modified Huffman, TIFF-Group III, TIFF-Group IV, TIFF-JPEG, WMF, WPG, XPM, XBM, XWD.

How do I convert CAD files to non-CAD files for archiving or distribution?

TracTrix can individually convert DWG, DXF and HPGL CAD files to high-resolution raster files. For batch conversion consider Trix RasterServer.

Is TracTrix a scanner?

TracTrix is software. It does not include hardware. TracTrix can either drive or use the raster output from practically every scanner available. If you do not have a scanner you will need to acquire one to run TracTrix (unless you plan to use a bureau for your scanning). Plan to purchase a scanner which generates at least 300 dots per inch resolution and if a small format scanner preferably one that supports the TWAIN interface. TracTrix also drives several large format scanners including, Contex, Ideal, Vemco, CalComp, Océ and WideCom. You should also look for a scanner which also scans and outputs in colour so that you can take advantage of TracTrix vectorization from coloured originals.

I have an old scanner. Will it work with TracTrix?

If your scanner can create a monochrome (also called bi-tonal or black and white - i.e. no shades of gray) TIFF, CALS or one of many other monochrome image file formats you can use TracTrix.
To use TracTrix colour vectorization you'll need a colour scanner.

Is there any way I can use TracTrix without a scanner?

The short answer is that TracTrix requires the type of image that scanners create. A more complete answer is that you do not need to own or acquire a scanner in order to use TracTrix.
You could go to a scanning bureau to have your scans done. Or you could try using your fax modem, although we don't recommend this approach.
Conversion Bureaus: You could have your drawings scanned at a bureau, put the images on disk, tape or CD ROM and use these stored raster images as input to TracTrix.
A disadvantage of this approach is that you will not be able to experiment easily with scanning difficult images - dirty, dilapidated or cluttered ones - so that they vectorize optimally.
You and your bureau should establish clear quality control procedures for the scans, preferably after running a pilot study using a good sample of your drawings. Alternatively, for large conversion projects, you may want to consider contracting out all the work to a conversion bureau. 
Legacy Scans: If you already have stored binary images from previous scans, they can probably be taken into TracTrix with no problem. Some experimenting may have to be done to achieve this. For additional help with poor quality images ask us for advice.
Aperture cards: Few companies have an aperture card scanner. But many have aperture cards and an aperture card viewer. Aperture cards can be scanned by a bureau and the raster file delivered to you on disk or tape. These files can then be opened and converted by TracTrix.
Using a Fax image: We know of users who fax drawings to their computer's fax modem (using the fine setting) and open the stored fax image in TracTrix to create vectors. However we don't recommend this approach. TracTrix works best with images of at least 300 dots per inch or 400 dots per inch. Normal fax standards do not support this level of resolution.

What will I save by using TracTrix?

Exact savings depend upon the quality of the original drawing and the type of image being brought into CAD. Some users report costs savings as high as 80% against conventional methods such as complete redraws, tablet digitizing and heads-up digitizing. And for some images, such as contours, automatic vectorization by TracTrix saves even more.
Taken over a library of original drawings we think you might realistically expect that the total time required to scan, vectorize with TracTrix and perform post-conversion tidy-up would be around 50% of what it would take for manual redrawing in CAD. However, every user's originals are different.

What will I gain by using TracTrix?

This question is a bit different from 'What will I save..? TracTrix has opened new methods to the 'time to market' issues so important to today's manufacturers. Many companies employ TracTrix to shorten time to manufacture by allowing sketches and other irregular drawings to be rapidly taken into CAD format for use in numerically controlled milling machines, machining centers, laser, water jet and plasma arc cutters.
Manufacturers are able to start with less than perfect originals and use TracTrix technology to produce samples and finished parts in a fraction of the time previously taken.

What does TracTrix do with text, symbols - Optical Character Recognition (OCR) ?

From our experience, text on engineering drawings, especially numerals and angled text, is very difficult to capture adequately with conventional OCR technology.
Hand drawn letters and numerals often look alike and are very difficult for the eye to discern. For example, we find that the hand drawn 'B' and '8' are quite frequently mistranslated, a poorly formed capital letter 'G' is often mistranslated as a '6' and vice versa.
Text at any significant angle to the normal axes is missed entirely. Post OCR editing time to find and correct the things that were missed or worse, erroneously translated, often takes longer than keying in all the text. The comments for text apply equally to symbols.
TracTrix has a unique text recognition technology. When initiated it searches for text regions and isolates them from the drawing line work itself.
The text recognition in TracTrix will either convert the identified text regions to CAD characters by its built in OCR or allow you to 'train' it to recognize the uniqueness of the characters in your particular drawing or set of drawings.
If font-based text is not a requirement, text areas can be selected for vectorization using TracTrix outline mode. This produces very readable text in vector lines rather than a vector font.
Alternatively, if the text is too unreadable to convert automatically TracTrix provides tools to create font-based vector text. In TracTrix the user manually enters the text in vector overlay mode, then deletes the raster text underneath.
Trix Systems is continuously reviewing OCR and pattern recognition technology in order to improve and enhance TracTrix. Recognition of shapes is not yet available - this 'pattern recognition problem is similar to that encountered with OCR - but the techniques available for our present processors are just not satisfactory.

Can I just vectorize what I want and not the whole drawing?

Yes. TracTrix allows "windowing" around that portion you wish to vectorize.

Does TracTrix despeckle or eliminate "noise"?

Despeckling or noise elimination means eliminating small groups of pixels which create visual 'dirt' or visual clutter in a raster image. TracTrix settings allow the user to define the minimum size of object to be vectorized. In this way 'dirt' is ignored and not vectorized.

Does TracTrix do orthogonal adjustment?

Squaring up corners is referred to as orthogonal adjustment. TracTrix provides this facility. It also allows you to adjust the whole of or parts of a vector image to be absolutely vertical or horizontal.

Does TracTrix recognize circles?

TracTrix recognizes circles as well as arcs, lines, polylines and Bezier curves.

How far can TracTrix zoom in?

It can zoom enough so that the user can see down to the single pixel level.

Can TracTrix show a vector over a raster?

Yes, this is a facility in TracTrix and is a useful way to check that the vectors represent the raster image.

Can TracTrix show dimensions in metrics and/or inches?

Yes, either one, it's users choice each time it's used.

Can TracTrix be set to jump a gap in a line?

Incomplete or broken lines can be edited, in the raster with our raster editing tools or as vectors, into complete or single lines within TracTrix or as vectors in your CAD software.

How many layers can TracTrix put vectors on?

TracTrix can create and place vectors on a near unlimited number of layers. This is achieved by identifying in advance the different raster line widths to be vectorized then each set of line widths is placed on different layers after vectorization.
TracTrix also recognizes offset spot colours. It will vectorize each different colour and place the resultant vectors from each colour on different layers. This too will provide an unlimited number of vector layers.

Can I use TracTrix without a CAD package?

TracTrix installs on your CPU as a standalone conversion tool that does not require a CAD package and as an object ARX application that runs within AutoCAD. No separate license is required. TracTrix Desktop 2 is a standalone package. Most users do have a CAD package into which the resultant TracTrix vectors are taken either before or after editing in TracTrix. Some NC users take their cutting input files directly from TracTrix.

How does TracTrix raster-to-vector conversion work?

An algorithm in TracTrix is designed to seek the pixels in the raster image and 'follow' them according to the parameters set by the operator. These include following the edge line of pixels in the 'Outline' following mode or following the centerline of the selected line width of pixels in the 'Centerline' following mode.
Additionally, TracTrix can be set optionally to create vectors as lines, arcs, circles, polylines, Beziers, NURBS or splines. The original image and desired file type often dictate the mode selected.

Definitions

DXF
DXF is one of many vector file formats used for the storage and exchange of CAD drawing data between different CAD software applications.

Hybrid file
A file containing both raster and vector information.

ISO 9000
ISO 9000 is an international certification of company quality standards established by The International Standards Organization (ISO), headquartered in Geneva Switzerland. Certification may be required in order to do business in certain industries, in certain countries, with certain companies and many government agencies. There are also other ISO standards with different numbers governing different types of businesses and technologies.

Line following
Line following software vectorizes interactively. The operator watches as the software tracks along the lines in an image and intervenes if an error is made. This is slower than automatic vectorization but can produce better results in certain types of complex images. Line Following will be supported in a future release of TracTrix in conjunction with other major technical advances.

Splines, B-splines, NURBS and Bezier curves
A spline or B-spline curve is a blended piece polynomial curve passing near a given set of control points. The blending functions are the type that provide more local control compared to other curves like a Bezier curve. A Bezier is a polynomial curve passing near, but not necessarily through, a set of given points.

A Bezier curve represents an equation of an order one less than the number of points being considered. A NURBS (Non uniform rational B-spline) is a B-spline curve or surface defined by a series of weighted control points and one or more knot vectors.

TWAIN
TWAIN is driver software which enables applications software such as TracTrix and other graphics applications to communicate with and drive your scanner. Once you've set up an application to use TWAIN, its presence should be almost invisible to you. Created by Hewlett-Packard, the TWAIN standard is now widely used by other small format scanner manufacturers.