All About Raster to Vector Conversion

Hello out there.  It’s a new week, and we have the scanners warmed up, the technical guys and gals in front of their computers and we’re rolling.  I love coming to work!  Every day is different.  Every project brings new challenges. 

At the end of last week, I was talking to some folks about a CAD Conversion job they want done.  We were specifically discussing raster to vector conversion.  I thought that some of the questions that came up in our conversation would make for a good blog entry this week.  So…here goes…

What is raster to vector conversion?

According to Wikipedia, “vectorization refers to the process of converting raster graphics into vector graphics.”    In very simple terms, this means converting pixels, which are dots of color (raster) like this

 . . . . . . . . . . . into lines (vectors) like this __________.    When you enlarge a raster image, the dots or pixels begin to break apart, like this .   .   .   .   .   .   .   .   .   .   .  and you lose the clarity of the image.  (Think about enlarging a photo taken with your digital camera.  On the other hand, a vector image can be enlarged indefinitely without loss of integrity, like this________________________ because it is made of lines, arcs, polygons, etc. 

Why is this concept important?

When you design in CAD, (Computer Aided Design) you have to work with lines, just like you would draw with a pencil, if you were designing on paper.   Here are some sample AutoCAD files. 

How do you convert from raster to vector?

This is where the “magic” comes in, better known as experience and know-how.  CadCam Services uses many different conversion methods. We use CAD conversion products from, GTX, Hitachi, I/Vector, and Softelec.   In addition we have quite a few routines and conversion programs we’ve written ourselves.  Unfortunately we have found that one R/V conversion product does not fit all. It is not uncommon with 100 drawings, that 30% are converted via one (1) method, the next 40% are converted via a different method, and the remaining are hand redrawn. Please do not be mislead with R/V software vendors promising ‘automatic raster to vector conversion’. Simply put, it is not true. These products are tools – and only tools. They all help in our conversion process, but they are not the cure-alls they claim to be. We spend hours, and hours inside of your drawings to get them to be 100% correct.   

Next week, we’ll talk about CAD Translations.

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Converting Paper Drawings to CAD Files

We have lots of large format scanning and file conversion jobs going on in our cad conversion shop this week and as usual our scanning and raster to vector conversion experts are going full steam ahead.  One of our more interesting jobs this week is the scanning of hundreds of old construction drawings to bring into a CAD system for update.  It occurred to me that it would an interesting topic to discuss just how we here at Cad/Cam perform the scanning and cad conversion process.

Scanning

The process starts with a high quality scan. The only large format scanners we use to scan work for raster to vector jobs are 4-camera scanners. Image quality is everything here. If two lines are muddied up and appear as a single line how can our drafters know they should be separate? All of our R/V scanners sell for ~ $28-30,000. Once we have the best scanned raster image possible, we rectify the image to make sure it is aligned correctly, scaled correctly, and rectified to make sure it measures correctly on all axes points.

Cad Conversion

We use several different methods to convert drawings into CAD. Sometimes we use heads up digitizing, sometimes we use commercial R/V software, or sometimes we use our own custom written CAD conversion scripts and software. We use the method that provides the best end result CAD conversion for our customers.  We’ve spent years refining this process. Again, one process does not fit all. If you need 100 drawings converted, we might do 30 one way, 30 another, and 40 a third way. There is a learned art to this CAD conversion process. On large ongoing projects we even set up dedicated teams who work only on one project throughout the entire year.

Quality Control

All work is checked by a different member of our drafting department. Our staff shifts to keep the drafters and checkers fresh. All are experienced with a minimum of 3 years of CAD work.  We guarantee our work to be 100% correct, 100% of the time.  No exceptions.  No excuses.

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