Parent Category: Big Blue Saw Blog
Created: Tuesday, 05 January 2016 17:01
Written by Simon Arthur
Our online quoting and ordering system works best with files in the DXF or DWG format. That's because these two file formats have nearly universal support in CAD software as well as in the waterjet and laser cutting world.
Significantly, these file formats are vector formats. As a quick recap: image files generally fall into one of two types -- vector files and raster (AKA bitmap) files.
Raster files consist of a regular grid of pixels, each of which has its own color. Think of a mosaic picture made using only square tiles of the same size. Or coloring in the squares on a sheet of graph paper.
Popular formats for raster files are JPG, GIF, and PNG. These files are typically created by digital cameras, scanners, and software like Windows Paint, Gimp and Photoshop.
A raster image is made up of pixels filled in with colors. In this image, the area in the red rectangle on the left has been zoomed in on the right so that you can see each pixel.
Vector files, on the other hand, create an image from a set of precisely defined lines and curves. Vector files are produced with CAD software like AutoCAD, DraftSight, etc. as well as by drawing programs like Inkscape and Adobe Illustrator.
A vector image is made of curves and straight lines. In this picture, you can see the end points of the lines as well as the control points that make up the curves.
One nice thing about vector files is that they can be zoomed or scaled and the lines look just as smooth. When you zoom in on a bitmap embedded within a vector file, this is not the case.
Unlike a raster image, a vector image can be resized or zoomed without losing any detail. The letters on the left look round even when made much bigger, as shown on the right.
When it comes time to make parts using waterjet cutting or laser cutting, we need a vector file because this gives the exact outline of the shape and a path for the cutting tool to follow. Astute users of our service will notice that uploaded GIF and PNG files are converted to DXF by a tracing process on our servers when the quoting process begins.
The Confusing Thing
Strangely, files can contain both bitmap AND vector data! This happens commonly when exporting to a vector format from a bitmap-oriented editor. When a vector file contains an embedded bitmap, the embedded bitmap does not have the exact outline of the shape and a path for the cutting tool. It's still a bitmap and shares the limitations of all bitmaps.
DXF, PDF, and SVG all support embedded bitmaps to coexist with vectors.
How to Tell If Your Vector File Has an Embedded Bitmap
One way to tell if a file has an embedded bitmap is by zooming in. You will be able to see the jagged edges of the pixels in the bitmap image once you zoom in far enough.
An overview of a CAD design in Inkscape. It looks just like a vector drawing at this zoom level.
Zoomed in, you can see the telltale jagged outline of an embedded bitmap.
Another way to check for embedded bitmaps is to use the outline view mode of your editor. In Inkscape, that's done by choosing View > Display Mode > Outline from the menu. An embedded bitmap will then be shown as a plain rectangle with an X in the middle. In this view, true vectors will be shown with their original path, but with alll styling (colors, thickness, etc.) removed.
Outline view in Inkscape.
The same design as a vector, zoomed in.
If you need free or low cost software that will create vector files for your design, take a look at our list of recommended software. Then learn how to format your CAD files for our online quoting system to make custom parts from aluminum, steel, plastic, and more.