Vector Graphics

• General Information
      Raster File Formats
      Vector File Formats
• Vector Layers
• Node Editing
• Vector Text
• Exercise 8 – Creating a Vector Cat

General Information . . .

Comparing Raster and Vector File Formats

Raster File Formats

A Raster image is composed of units of light, called pixels, which are laid out on a grid. If you increase the magnification of an image, you can see these pixels. They appear as squares in the screen. A Raster program creates objects by grouping pixels. An object is stored as a group of pixels with information about each pixel color. Pixels can be blended to create soft edges and smooth transitions between objects. This makes the format a good choice to use for saving photographs.

An image in the Raster format is resolution-dependent. You specify the resolution and pixel dimensions when you create the image. If you later decide to increase its size, you enlarge each pixel, which lowers the image quality.

Vector File Formats

A Vector image is composed of mathematical instructions for drawing the image. Each object in a Vector image is stored as a separate item with information about its relative position in the image, its starting and ending points, width, color, and curve information. This makes them suitable for logos, fonts, and line drawings.

An image in the Vector format is resolution-independent. It can be resized without losing detail because it is stored as a set of instructions, not a collection of pixels. Each time you display an image, you recreate it. See "Exercise 8", part "f " for additional information on vector formats.

Note that a computer monitor uses pixels to display an image, and most printers convert pixels to ink dots. Vector images are rasterized (created using pixels) when displayed on the screen or printed. When you close them, they are saved in the Vector format.

Below are some of the more common vector formats. . .

Vector Layers . . .

A vector layer does not use pixels for storing image information. Instead, it stores a vector object as a set of properties that describe its attributes, dimensions, and position in the image. Each time an image is opened, these properties are used as instructions for drawing the objects. Because the objects are independent elements, you can move them without affecting the rest of the image.

You can add vector layers to images of color depths that are too low to support raster layers. While only greyscale and 24-bit color images can contain multiple raster layers, images of any color depth can contain multiple vector layers. When you reduce the color depth of an image, Paint Shop Pro merges both raster and vector layers. You can then create new vector layers in this image, even if it does not support raster layers.

The Layer palette displays the vector icon to the left of a vector layer button. When the layer contains vector objects, a plus sign appears next to the icon. Click it to display the buttons of all the vector objects on the layer.

You cannot place vector objects on raster layers or raster objects on vector layers. If you try to create a vector object on a raster layer, Paint Shop Pro automatically creates a vector layer for you. If you are working on a vector layer, Paint Shop Pro merely adds the new object to the layer.

The Drawing , Preset Shape , and Text tools can create both vector and raster objects. Use the tools as vector tools on vector layers and raster tools on raster layers. There is also a tool for editing vector objects called the Object Selector tool . It cannot be activated unless a vector layer is current (active).

Node Editing . . .

What is a node?

A node is a control point. Every vector object contains a path, which is composed of at least one contour. A contour contains at least two nodes, or control points, and the segments that connect them. A contour is a mathematically described path, it starts at a node and ends at a node. References: JASC, “ Paint Shop Pro”, Help; &  http://www.zdwebopedia.com/Graphics/vector_graphics.html an on line reference.

A node is a control point on a vector object. The type of each node dictates the shape of the line segment on either side of it. A node and its control arms influence the shape of the entering and exiting segment. For example, to make smooth curves, use a node with symmetrical control arms. 

All drawing points (nodes) have two handles extending from them. These handles determine the shape of a contour. A handle can have a length of 0. Two opposing handles from sequential nodes having zero length form a straight line segment. A curve is formed if one or both opposing handles of sequential nodes have length.

There are three types of nodes:

· Tangent node

· Corner or cusp node, and

· Curve node, either symmetrical or asymmetrical.

When working with nodes:

· In Drawing and Edit mode, press the <Ctrl> key while left-clicking to add nodes along the contour,

· In Drawing and Edit mode, use the left mouse button to move the nodes or reshape the curves.

· In Drawing and Edit mode, right-click to choose context menu commands.

Accessing Node Edit . . .

Use one of the following methods to enter the Node Edit function:

· Activate the Drawing tool by clicking its button on the Tool palette or the Tool Options palette Tool Selection menu, and then select Point to Point from the Type drop-down box on this palette’s first tab.

· Activate the Object Selector tool by clicking its button on the Tool palette or the Tool Options palette Tool Selection menu, and then right-click a Vector object other than text and choose Node Edit from the context menu.

· Activate the Object Selector tool, click a vector object other than text to select it, and then click the Node Edit button on the Tool Options palette.

Exiting Node Edit . . .

Use one of the following methods to exit the Node Edit function:

· Press the <ESC> key. Paint Shop Pro exits the mode without applying any changes.

· Right-click a node and choose Quit Node Editing from the context menu. Paint Shop Pro applies the changes and exits the Node Editing mode.

· Press <Ctrl> + <Q>. Paint Shop Pro applies the changes and exits the Node Editing mode.

· Click outside the image.

When you exit the Node Edit function, Paint Shop Pro applies color to the path and deletes single nodes not connected by segments. To return to Node Edit, use any method described above.

Below are examples of nodes and actions you can use with them. . .

1.  By using the "Preset Shapes" tool, tool options "Star 1".  Notice the whole object is a group of nodes.

2  Using the "Vector Object Selection" tool, and right clicking inside of the group, and selecting "Node Edit".  Notice that now individual nodes are available to position.

3.  Four of the nodes were dragged to a new position.

4.  While in the "Node Edit" mode new nodes were added (by holding down the Ctrl key and clicking on a line segment when the word "add" appeared by the cursor) and then dragging two of them to a new position.

5.  Node editing was exited (by right clicking), when the group was displayed, similar to figure 1. the small square to the right of the center was used to rotate the entire figure.

6.  This was achieved by right clicking inside of the group and selecting "Properties".  The fill style color was then changed from white to green.

Vectors are very "neat" in to days vernacular.  They are very powerful and deserve our attention.

Vector Text . . .

Use the Text tool to create raster and vector text. Vector text, which can be moved, deformed, and edited after it is created, can only be placed on vector layers. If you create vector text while working on a raster layer, Paint Shop Pro places it on a new vector layer.

To position the text, click the point on the image where you want to place it. Clicking the image opens the Text Entry dialog box. To create text on an existing layer, click that layer’s button on the Layer palette.

You can create text in one of three modes:

· As a raster selection on the current layer,

· As a floating raster selection above the current layer, or

· As a vector object on a vector layer.

Vector text can be created only on vector layers. If necessary, Paint Shop Pro creates a new vector layer. The text is a vector object that can be edited, deformed, and moved. Text is placed horizontally unless you have created it on a path. Shown below is something you can do to a simple "HELLO".  When created on a path, the text follows the path.

The Hyper-Link title above was created using Vector Text.  It is left as an exercise for class members to create text which follows a Bezier Curve.  The curve tool is found under the tool options menu for the draw tool button.  Once the curve is drawn you merely select the text tool and click for a starting point on the curve.  You then follow the directions in the text tool window.

Click on the image, it is a hot-link to the exercise where you will learn the BASICS of constructing vector objects and combining them into a vector image of a cat.

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