tracing, continued - page 1, 2, 3 & 4

Tracing is a technique used by sign-makers that allows them to preserve as much of the original bitmap file as possible, whilst allowing them to scale up and down a design without the loss of quality you saw on the previous page.

The process is also known as 'vectorizing' since the file-format and method used to rebuild the design utilizes vector drawing packages in comparison to bitmap drawing packages. Adobe Illustrator, Corel Draw, Zoner Draw and InkScape are all examples of vector-based drawing packages. Adobe Photoshop, Microsoft Paint, Paint-Shop Pro and Corel Painter are all examples of bitmap-based packages. I use Corel Draw X3 for most of my work.

'Vector' is a posh word that translates roughly into 'based on math'. It describes shapes. For example a square can be described as a closed shape consisting of 4 equal length sides, with ninety degree angles. It doesn't matter how large or small you want that square, the rule - or 'vectors' still applies.

The problem becomes how does a bitmap file - which is a collection of dots get 'described' (or 'vectorized')?

If the original file is suitable, then an automatic process can be used. If however the file is very small and is packed with intricate detail then it will be necessary to 'trace' the file by hand.

Tracing is the process of essentially redrawing the entire design but using vectors.

In most cases the sign-maker will load the bitmap into the vector drawing package and then carefully place curved lines to 'trace out' the edges of the shapes in the bitmap. An example is shown to the right. The bright red line indicates the edge of the 'trace'. This is a very rough example, a lot more fine-tuning would be required before this 'vector' could be used.

However, as you can see, the curves are much smoother than the underlying 'm'. These curves remain smooth regardless of how large (or small) the design becomes since they are based on a set of mathematical rules that describe the shape.

 

 

Eventually the design will have been completely recreated using vectors. It will now look something like the image to the left. The original bitmap image is now discarded.

Notice how 'crisp' the outcome looks compared to the previous examples. This new format can be scaled, rotated and manipulated without loss of quality.

continue to page 3