TECHNICAL SUPPORT | How Illustrator Works

Vectors and Rasters

There are two main types of picture making applications:

Bitmap programs are ideal for creating painterly effects and photographic images. Photoshop is usually used for this type of image.

Bitmap art is created from pixels on a grid. Unlike vector art, bitmap art loses detail when scaled to a larger size.


Object-orientated (Vector art) programs are ideal for creating sharp, smooth, graphic images, like logos and type. Illustrator is usually used for this type of image.

Vector art is is created using mathematical algorithms executed by the PostScript page description language. Illustrator can create lines and shapes that are perfectly straight or curved, even if you move or resize them. You will able to draw precise lines and shapes at any size with any stroke weight, fill them with color, pattern or make them transparent.

 

More info and a short overview.

Even more info on using Vector Applications

 

Following is a comparison between the qualities of a Vector Image and a Bitmap Image:

VECTOR BITMAP
  • composed of separate distinct objects
    (mathematically defined paths)
  • pixels in a grid
    composed of tiny squares on a grid
    (pixels)
  • scalable:
    recoloring, resizing, reshaping an object will effect the entire object selected without diminishing its sharpness or smoothness
  • each pixel or "bit" in the image contains information about the color to be displayed
    recoloring, resizing, reshaping a part of an image will only effect the pixels selected in that image, not the entire object.
  • no background
    not restricted to a rectangular shape like bitmaps
    vector objects can be placed over other objects, and the object below will show through.
  • restricted to rectangle
    minimal support for transparency - GIF and PNG
    Photoshop support transparency, but only in native format
  • objects will look sharp regardless of the size displayed or printed
  • fixed resolution
    cannot be resized without losing image quality
  • generally small file sizes
  • files can get quite large
    often compressed to reduce their size
  • resolution independent:
    the higher the resolution of the printer, the sharper the printed image
  • resolution dependent
    print quality is dependent on the resolution of the image
  • primarily originate from software
    can't directly scan an image and save it as a vector file
    easily converted to bitmaps - rasterizing
  • easily converted
    all scanned images are bitmaps
    all images from digital cameras are bitmaps
    converting between bitmap formats is simple
  • ideal for creating logos, graphic images and illustrations
    made up of solid areas of color or gradients
    cannot easily depict continuous subtle tones
  • ideal for creating subtle tones and gradients, digital paintings, photorealistic images
  • Common vector formats include:
    AI (Adobe Illustrator), CDR (CorelDRAW), CGM (Computer Graphics Metafile), SWF (Shockwave Flash), and DXF (AutoCAD and other CAD software)
  • common bitmap-based formats:
    JPEG, GIF, TIFF, PNG, PICT, and BMP

 

How Object-Orientated Objects are made and modified

The three building blocks used to compose an illustration in Illustrator are:

Bezier objects are composed of anchor points connected by curved or straight segments. The edge of an object is called it's path. Paths can be open (with two endpoints) or closed and continuous. You can close an open path by joining its endpoints or open a closed path using the Scissors tool.

Some Bezier tools - like the Rectangle, Ellipse, Polygon and Star - produce complete, closed paths.

Other Tools like the Pen and Pencil tool produce open or closed paths by clicking or dragging with the mouse. The Pen tool can be used to create as many corner or curve anchor points as needed to form an object of any shape.

The Paintbrush tool can be used to create calligraphic, scatter, art or pattern brushstrokes.

There are six Type tools for creating PostScript type with features for style and formatting: point type, path type, area type - vertically or horizontally. Type can also be converted to outlines which can then be modified like any other vector object.

Bitmap images may be placed and included in an illustration or traced as Template using the Pen tool or the Auto Trace tool.

Layers are used to keep track of various elements in an illustration and can be restacked and toggled on or off for displaying and printing.

Objects must be selected before they are modified. There are five tools for this:

Objects are then modified using menu commands, filters, dialog boxes, palettes and tools.