Information about Rasters and Vectors for PhotoDraw 2000 Users 

Computer imaging and graphics programs deal with two basic types of objects, rasters and vectors:

• A raster object, also known as a "bitmap," "paint object," or "image," is a collection of small dots (pixels) arranged in a pattern. Paint programs, such as Microsoft Paint, and imaging programs, such as Microsoft Image Composer and Microsoft Picture It!®, let you create and edit raster objects. Raster objects produce subtler shading than vector objects, but they also produce larger files. A photograph is a good example of a raster object. When you zoom in on a photo, you can see its individual pixels.
• A vector object, also known as a "draw object" or "graphic," is a collection of lines that use mathematical descriptions to determine their position, length, and direction. Illustration programs and drawing programs let you create and manipulate vector objects. Vectors give you crisper lines and produce smaller files than bitmaps. An AutoShape that you create in a Microsoft Office program is a good example of a vector object. Its lines are smooth at any zoom level, whereas a raster line would look jagged at high zoom levels.

Traditionally, you would use a paint or imaging program to work with raster objects, and a separate graphics program to work with vector objects. Microsoft PhotoDraw™ lets you create and edit both types of objects without requiring you to switch between different programs.

Which Is Which?

You can tell the difference between rasters and vectors when you edit an object in PhotoDraw. Since vector objects are mathematically recalculated and redrawn when you edit them, they retain their original clarity and crispness. For example, if you stretch a vector line that you drew, its length is calculated based on its new start and end points, and then its color and width are reapplied.

Original vector object	... enlarged 200%	... enlarged 400%

But if you stretch a raster line that you painted, more pixels are added to the line, which can produce jagged edges. When you shrink a painted line, pixels are removed to reduce its overall size, which can make it appear distorted.

When Vector Objects Become Bitmaps

Each type of object you create in PhotoDraw begins as either a raster or vector object:

PhotoDraw object	Raster or vector?
3-D	Raster
Line	Vector
Paint stroke	Raster
Photograph	Raster
Shape	Vector
Text	Raster

But certain tasks that you perform on vector objects change them to raster objects. For example, when you touch up or apply an effect to a vector object, it becomes "rasterized." For example, if you draw a line (a vector object) and add a drop shadow to it, then the line becomes a raster object. Similarly, if you fill an AutoShape (a vector object) with a picture (a raster object), then the shape becomes a raster object as well. Note that the converse is never true: raster objects cannot become vector objects.

Understanding when a vector object is rasterized is important because it affects how you can edit that object. For example, you can edit the points of an AutoShape only while it's still a vector object. If you apply a 3-D effect to that AutoShape, it becomes rasterized. At that point, you can move and resize the object, but you cannot edit its points. Also, resizing a line or shape that has become rasterized may cause its edges to become jagged, as illustrated above.

Tips for Working with Vectors and Rasters

Suppose you create a vector object, and you want to edit it in such a way that it becomes rasterized. Because you cannot edit the individual points of a raster object, it's generally a good idea to wait until the vector object looks just the way you want before you apply raster effects to it.