Applying Actions

Actions are processes that can be applied to the images attached to cells within the container/image viewer. LEADTOOLS supports several standard or "built-in" actions and custom or "user-defined" actions.

Built-in Actions

LEADTOOLS supports the following built-in actions:

Window Leveling: Maps grayscale intensities using a user defined color map (LUT).

Alpha: A window-leveling factor used when the window leveling lookup table is not linear.

Scale: Increases or decreases the size of the image in the cell.

Offset: Changes the offset of the image within the cell.

Magnifying Glass: Magnifies the image in the cell.

Stack: Scrolls the images within the cell.

Annotation ruler: adds a ruler object to the cell.

Annotation rectangle: adds a rectangle object to the cell.

Annotation ellipse: adds an ellipse object to the cell.

Annotation angle: adds an angle object to the cell.

Annotation highlight: adds a highlight object to the cell.

Annotation arrow: adds an arrow object to the cell.

Annotation text: adds a text object to the cell.

Rectangle region: adds a rectangle region to the cell.

Square region: adds a square region to the cell.

Elliptical region: adds an elliptical region to the cell.

Circular region: adds a circular region to the cell.

Free hand region: adds a free hand region to the cell.

Polygon region: adds a polygon region to the cell.

Magic Wand region: adds a magic wand region to the cell.

Color Range region: adds a color range region to the cell.

Custom Actions

Custom actions are completely controlled by the user, including any mouse movement and keystroke association. These are handled through the LImageViewer::ActionCallback function. This callback function must be set by setting LImageViewer::EnableActionCallback to TRUE.

Adding Actions

Regardless of whether the action is built-in or custom, any action must be added to a container before it can be used. To add an action to a container, call LImageViewer::AddAction. Since the Image Viewer supports custom actions, there is no limit on how many actions a container can have. However, an action cannot be added to a container twice. To determine how many actions are currently in a particular container, call LImageViewer::GetActionCount.

Next, assign a mouse button or a keyboard key to the action. To assign a mouse button to the action, call  LImageViewer::SetAction, and pass the action and associated mouse button values together. An action can only be assigned to one mouse button.

To assign a keyboard shortcut to the action call LImageViewer::SetKeyboardAction. To get the current keystroke combination associated with a specific action, call LImageViewer::GetKeyboardAction.

Once the action has been added, it is considered "active". To determine whether a specific action is active, call LImageViewer::IsActionActive. To check whether the button or the flag is valid to be assigned to the specific action, use the function LImageViewer::IsButtonValid.

The LImageViewer::SetAction function also lets the user decide whether the applied action will affect one cell, selected cells, or all cells in the container, and whether the action is applied during mouse movement or after mouse button release. You can also retrieve the assigned mouse button and flags to the specified action by calling the function LImageViewer::GetActionButton.

Action Properties

Each action has both general and specific properties. The general properties, like the cursor, are common to all cells within the container. These are applied at the container level. Specific properties, such as the width used by the window level action, are used to manually change values used by the action. These are applied at the cell level. The properties used by each action are contained in an action-specific structure.

Action properties that apply to the entire container can be found in the DISPCONTAINERACTIONPROPS structure. Each of the action-specific structures contains a DISPCONTAINERACTIONPROPS structure, as well as other properties, related to the specific action. Some of the additional properties related to the specific properties are also applied at the container level and are therefore "general" properties, while others are applied at the cell level and are therefore "specific" properties.

The current properties associated with a specific action can be retrieved by calling LImageViewer::GetActionProperties. To change the properties for a specific action, call LImageViewer::SetActionProperties. When an action is no longer needed in a container, it can be removed by calling LImageViewer::RemoveAction.

How action works

Any action must be added to a container before it can be used. To add an action to a container, call LImageViewer::AddAction. Next, assign an action to a mouse button by calling LImageViewer::SetAction, or assign an action to a keyboard key by calling LImageViewer::SetKeyboardAction.
For example,  if the “Window Level” action is assigned to the left mouse button, when the user clicks and hold the mouse button, then drags in any directio,. the brightness and contrast of gray image will be changed according to the direction of drag.
LImageViewer::SetKeyboardAction allows you to set a keystroke to imitate the mouse movement in any of four ordinal directions. For example, assign  the key Shift + Left to initiate the same effect as dragging the mouse to the left.

The following describes action behaviors when it is assigned to a mouse button:

For more information on the properties of the various actions, refer to the structures listed below:

DISPWLEVELACTIONPROPS

DISPALPHAACTIONPROPS

DISPMAGACTIONPROPS

DISPOFFSETACTIONPROPS

DISPSCALEACTIONPROPS

DISPSTACKACTIONPROPS

DISPOWNERACTIONPROPS

DISPANNOTATIONPROPS

DISPREGIONPROPS