Illustrator
Introduction
Illustrator is 2D vector graphics editing software. It can be used to make presentation posters, diagrams, drawings, and so on.
Contents
Background
It is important to familiarize yourself with some important terms that are involved in working with illustrator:
Vectors and Pixels
Vectors
Vector images consist of lines and shapes that are mathematically describes. Therefore vector graphics are always sharp, no matter how far you zoom in; the precise shape is calculated.
Vector graphics don't have a 'resolution', which is used as an indicator for quality in raster images, which means they can be scaled to any size and printed at any resolution without losing detail or clarity.
Vector graphics are well-suited for line drawings, schemes, graphs and such. Since vector objects can only depict a single color or simple gradients, they are not suited for depicting photographs or other images with subtle, irregular and multi directional color differences.
The example at the right shows a typical drawing made in Illustrator, where the sharpness and precision of the program result in better control over the lines and drawing as a whole.
Examples of vector formats are:
- DXF/DWG (AutoCad)
- AI (Adobe illustrator)
- CDR (Coral Draw)
There are also some formats that are mainly vector based, but often also contain bitmap information. Some examples:
- PDF (Adobe Portable Document Format)
- SWF (Macromedia Flash)
- WMF (Windows Metafile)
Software for creating and editing vector files:
- Adobe Illustrator
- Inkscape
- CorelDraw
- Autodesk Autocad
Pixels
Pixel or raster images are the most commonly used type of images. Digital photos are raster images, for example. Generally speaking, they consist of pixels (squares) with a certain color value.
Often pixel images are referred to as raster images because an image consists of a raster or grid of pixels. Because raster images are based on pixels they have certain disadvantages. The main disadvantages becomes apparent when scaling or zooming-in to a part of the image. The raster becomes apparent and the image will no longer have sufficient detail for smooth shapes. This makes it impossible to scale a raster image without loss of quality.
Raster images can be edited with software such as Photoshop, GIMP, Paint and Paint Shop Pro.
The comparison
This example at the right shows a raster (pixel) version of a filled circle (left) and a vector version (right), which illustrates the difference between raster and vector images. A part of the edge is magnified. When magnifying, the saw-tooth pattern is clearly visible. Hence there evidently is a detail limit for bitmaps. When zooming in on a vector object, the shape can still be accurately calculated due to the mathematical equations.
Because of the elemental difference between pixel and vector images, the one is better suitable for certain types of images then the other. This becomes clear when comparing a pixel image photo to a traced (vector) photo. It is evident that the vector photo has a lack of detail and shade gradients. Therefore vectors are more suitable for line-art images, whilst pixels are more suitable for images that require subtle details in colors (photo's, hand-drawings a.o.).
The image below illustrates the difference of a photo (raster image) (right) and the same photo converted to vectors (left):
Adobe Illustrator can import pixel images, which makes it ideal for creating presentation posters. Because you can import, for example, your CAD drawings, and combine them with rendered images in one poster, without losing the sharpness of the CAD drawing (because it stays vector-based). If you were to make the presentation poster in Photoshop you would lose the sharpness of your CAD drawing, since Photoshop converts it into a raster image, a process called rasterizing, which undoubtedly will cause loss of quality.
Converting bitmap to vector
Converting bitmap to vector is a little tricky. The process is called tracing. A prerequisite is that the bitmap is suited for conversion. As a rule, images like photographs are not or less suited. Both Adobe Illustrator and Macromedia Flash offer tracing options. (The effect of tracing a bitmap has a similar effect as using the cut out filter in Photoshop).
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