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Raster to Vector Guides

Creating Vector Outlines of Raster Images

Be it for business, for design or for machining, many designers and CAD users will at some point have to deal with creating workable outlines out of reference images. But how do you go about doing so? And what do you do if your reference image is a raster image?

Chances are, if you’ve dipped your foot into the design or CNC fields before, you’re familiar with the differences between raster and vector. But for the beginners out there, the basic difference is that raster images are made of pixels and vector images are made or scalable, machine-readable “paths”. In practice, that means that raster images get blurry as you zoom in and vector images do not. When it comes to dealing with outlines for logo design, illustration, and CNC machining, vector images will always be the standard. But if you’re stuck with a raster image with an outline you need to use, there are a couple of ways we can go about converting an image for CNC.

Vectorized outlines of birds
Vectorized outlines of birds Source

The three main branches of conversion methods that you need to consider are manual conversion, online services (such as rastertovector.com’s ability to convert raster to vector for free online), and dedicated conversion software. Manual is just like what it sounds: you manually trace over the raster image to create an outline. There are also free and not-so-free online services that offer to automatically convert raster outlines to vector formats. And as for dedicated conversion software, some programs are specifically designed and are made commercially available to those seeking to do raster-to-vector conversions regularly.

Now, all these three methods have their own pros and cons. What’s best suited to each user will depend on their priorities and considerations. We’ll go through the three methods and by the end, hopefully, this would help you decide what proverbial route to take.

Manually creating vector outlines

Manually tracing using paper
Manually tracing using paper Source

Back in the day, drafters, illustrators, and machinists would have to set up a drafting desk with tracing paper and drawing implements just to produce a traced outline of their reference image. With the advent of CAD and vectorization, the process of manual drafting has gone surprisingly unchanged – just with digital tools instead of physical ones.

The idea is – if you need to produce a vector outline of a raster image, import the image file onto a CAD program and “trace” over the image with your CAD tools. It’s a simple and straight-forward process that needs little instruction from those familiar with CAD programs.

  1. Open up your preferred CAD software and ready up the plane or view where you want to place and trace your raster image.
  2. Import your raster image into the program and scale it accordingly.
  3. If the option is available, turn down the opacity of the image so that any lines drawn over it will be easier to see.
  4. Carefully follow the outline of the image with the various drafting tools available. If you’re working with digital illustrations, splines usually create smoother edges than arcs. For the purposes of CNC machining, however, arcs and polylines are the easiest to handle and most standard graphical elements for most CNC machines.
  5. Make sure to do a once-over after finishing up with all the drawn lines. You’ll want to make sure that there are no loose ends and then all lines, arcs, and splines connect to each other. This is less of an issue for digital illustrations but would be a very important step for CNC designs since CNC machines can much readily and efficiently handle optimized vector files.
Pros Cons
  • User has full control over the vectorization process
  • Process is the best for any raster images that are too blurry or pixelated for automated processes to handle
  • Easily the most tedious and time-consuming vectorization process
  • Can only be done when users are familiar with the use of CAD programs
  • Prone to human error
  • Not optimal for complex images including bezier-like shapes or when working with batches of multiple images

Online tools or services

Online vectorization
Online vectorization Source

So the first of two automated vectorization methods involves availing of online conversion services. These websites will typically ask users to upload a copy of their raster image and will either take some time to process the image and then churn out a downloadable vectorized version of the file or email you the said converted file.

These are ideal for those looking for an affordable and quick way to go about automatically vectorizing outlines as a one-off. Since not all websites are the same, you’ll be better off keeping realistic expectations when choosing a conversion website. “Free” websites will often come with a catch. Some websites will place a watermark, some will limit the number of files one can upload, and others will online work for raster images within a set resolution. Although it’s hit or miss with these websites, it’s safe to say that smaller vectorization processes are simple enough to do with online websites as long as users stay smart about what sites they visit.

  1. On the upload page of the conversion service, transfer in a copy of your raster image. Do note that since you’re required to give a copy of the raster image to a third-party, it’s important to make sure that there are no sensitive or confidential contents in the image.
  2. For some sites, they will require you to set up an account or register an email address.
  3. Make sure you keep within the limits of the online converter and ground your expectations by doing some research, i.e. the maximum file size or resolution for the input and output, whether the image has a watermark, or if there is a set amount of uploads or downloads from the site.
  4. With your preferred dedicated CAD program, double-check the final product and make sure that the lines are optimized and clean.
Pros Cons
  • Usually free to use
  • Easy and straightforward
  • Does not require any CAD or conversion programs to be downloaded since it can be done on your web browser
  • Not always consistently reliable
  • Requires you to upload files to a third-party website
  • Can only handle simple vectorizations
  • Will most likely have designer-set limits as to what you can achieve with it

Dedicated vectorization software

Scan2CAD vectorization of the Ford logo
Scan2CAD vectorization of the Ford logo

There are vectorization and conversion solutions that are either plug-ins into already existing CAD programs or are their own independent and standalone programs. CAD programs with added vectorization capabilities are few and far in-between, with most of their prices being a tad on the expensive side. And even after paying the premium for these programs, it’s quickly apparent that they aren’t the most customizable processes to execute.

Dedicated third-party programs are the best choices available and one such process is Scan2CAD. Programs like Scan2CAD are perfect for anyone who’s expecting automated conversion to be a regular need in their workflows. And with advanced object recognition, OCR capabilities, and customizable vectorization profiles, there are very few automated options out there that can hold a candle to dedicated vectorization programs.

  1. Open up your image file in your vectorization software. The most suitable images for vectorization will have the following criteria:
    1. Lossless file formats such as TIFF or PNG
    2. Scanned images at 300-500 DPI
    3. A minimal amount of colors, preferably monochromatic (black and white)
  2. With your conversion program’s editing tools, convert it to black and white if isn’t already monochromatic. Play around with the threshold level to get just the right amount of black pixels without adding too much graphic noise. Additionally, try to clean up any speckles and holes in the image to minimize any unwanted vectorizations.
  3. When converting to vector, choose your program’s designated ‘Outline’ settings. Tweak the settings to sharpen or smoothen out the resulting vectors.
  4. Take the time to do minor edits and vector optimization changes onto the resulting vector.
  5. Save the output by setting its name and file format.
Pros Cons
  • The most robust and versatile option
  • Quick and straight-forward
  • Can handle batch vectorizations and has no set limit to image complexity or file size
  • Perfect for regular vectorization needs
  • The priciest option
  • Has limits when dealing with extremely low-quality raster images
  • With editable settings, more involved than most online converters

The bottom line

If we were to rank the three methods in terms of efficiency, quality, and price:

Efficiency
  • Most Efficient – Dedicated software
  • Mid-tier – Online converters
  • Least Efficient – Manual conversion
Quality
  • Highest Quality – Dedicated software
  • Mid-tier – Manual conversion (depending on the skill of the drafter)
  • Least Efficient – Online converters
Price
  • Priciest – Dedicated software
  • Mid-tier – Manual conversion (still needs CAD programs)
  • Most Affordable – Online converters

So if you’re short on time and the outline vectorization process isn’t something you’re expecting to do too often, your best bet would be online converters. For those with a more regular need for vectorization solutions, dedicated software would be the best. And for drafters with a lot of extra time or for those raster images with just too little definition to be reliably vectorized automatically, you can’t go wrong with the manual conversion.

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