Implementing Annotations

Annotations are based on vectored drawing functions and are associated with bitmaps as an overlay of the displayed image. LEADTOOLS supports a number of annotation types, including lines, rectangles, audio clips, hotspots, redact objects, polygons, and containers. A container is a specialized annotation object that lets you position and group other annotation objects, including other container objects. For a full list of available annotation types, refer to Types of Annotations.

LEADTOOLS maintains annotations separately from bitmaps. Your application code is responsible for maintaining the relationships between images and annotations. For example, the annotation example that ships with LEADTOOLS, creates an annotation file that has the same name as its associated image file, but with a different extension. When the image file is loaded, the program looks for an associated annotation file and loads it as well.

The functions supported by LEADTOOLS let you create automated annotations or non-automated annotations, depending on your application’s requirements.

Automated Annotations

Automated annotations require an automation object to be associated with the top-level container, also known as the root container. This automation object lets you maintain default properties for all objects in the root container. For example, you can use it to set the default font and the default line width. Keep in mind, however, that scaling factors affect the appearance of these default measurements. The values are set based on the scaling factors that are in effect at the time you create the object. Features associated with automated annotations are:

Automated annotation menus appear when you right click in design mode. These menus may or may not include the hyperlink menu item.
Automated drawing lets you use the left mouse button to draw annotations in design mode.
The annotation toolbar lets you select the annotation tool to draw.
LEADTOOLS handles the activation of audio annotations and hyperlinks.
You can undo a number of user actions, executed using the automated annotations functions.

You can implement the automation using only a few supporting functions.

First, use the following function to create the root container:

L_AnnCreateContainer

Then, use the following functions to create and maintain an automation object:

L_AnnCreate

L_AnnCreateItem

L_AnnGetAutoBackColor

L_AnnGetAutoContainer

L_AnnGetDpiX

L_AnnGetDpiY

L_AnnGetFillMode

L_AnnGetTextFixedSize

L_AnnGetLineFixedWidth

L_AnnSetAutoBackColor

L_AnnSetAutoContainer

L_AnnSetAutoDefaults

L_AnnSetDpiX

L_AnnSetDpiY

L_AnnSetTextFixedSize

L_AnnSetLineFixedWidth

The following functions provide selection capabilities:

You can modify and enhance the automated features using other annotation functions and the WM_LTANNEVENT message.

Note:	In automation mode, the undo feature can cause the values of object handles to change. Therefore, if your application needs to identify the object that is activated or deactivated, you should use the tag property. The L_AnnSetTag function sets the tag, and L_AnnGetTag gets the current value.
Note:	The annotation example program that ships with LEADTOOLS is implemented using high-level automated features. For more information about the annotation demo, and to see an example of the automated user interface, refer to Automated User Interface for Annotations.

For information on creating an automated annotation program, refer to Implementing an Automated Annotation Program and Using Automated Annotations in Run Mode.

Non-automated Annotations

Non-automated annotations allow you to customize the creation of and interaction with annotations to suit your own needs. Any LEADTOOLS annotation function, except those requiring an automation object, can be used when working with non-automated annotations. When programming non-automated annotations, it is important to remember:

You must provide any menus or dialogs you wish to use for entering annotation data.
You must also provide your own means of drawing and interacting with the annotations.
No hyperlink activation is provided for non-automated annotations. In addition to providing the code for entering hyperlink type and associated parameters, you must also provide the code for accessing the default web browser and calling any programs to be run through a hyperlink.

For information on creating a non-automated annotation program, refer to Implementing a Non-automated Annotation Program and Using Non-automated Annotations in Run Mode.

For a list of functions pertaining to various aspects of implementing annotations, refer to:

Annotation Functions: Implementing Automation.

Annotation Functions: Working with the Toolbar.

Annotation Functions: Input and Output

Annotation Functions: Creation, Deletion and Copying

Annotation Functions: Global Properties

Annotation Functions: Size, Position and Shape

Annotation Functions: Object Properties

Annotation Functions: Display and Printing

Annotation Functions: Realizing to a Bitmap

For more information on annotations, refer to: