Getting and Setting Capabilities

Each TWAIN source may support a number of capabilities. These capabilities dictate the behavior of the TWAIN source. Before acquiring images from the selected TWAIN source, the user may wish to examine and change the capability settings for that source.

It is possible to check whether the installed scanner to the system supports certain capabilities. For more information, refer to How to Find Out Whether Your Scanner Supports Certain Capabilities Using Twacker, found on http://support.leadtools.com/SupportPortal/cs/forums/3781/ShowPost.aspx.

The LEADTOOLS TWAIN toolkit provides the user low-level and high-level functionality for getting and setting the capabilities.

LEADTOOLS provides both low-level and high-level methods for getting and setting capabilities. The low-level methods get and set capabilities individually. The high-level methods let the user get and set a specific group of capabilities, be getting and setting properties in a structure.

Low-Level:

$image\sqrblit.gif$ To get information about the capabilities supported by the selected TWAIN source, set EnableEnumCapabilityEvent property to TRUE and call the EnumCapabilities method. For each capability enumerated by EnumCapabilities, this method will generate the OnEnumCapabilityEvent Event. Within this event the user can process the capability information.

$image\sqrblit.gif$ To get information on a specific capability (current, default, or all possible values) call the GetCapability method. This method gets information about the capability specified in a TW_CAPABILITY structure. For more information about TW_CAPABILITY, refer to the TWAIN 1.9 specification from the site www.twain.org.

$image\sqrblit.gif$ To set a specific capability to a new value or to reset the value of a capability to the default value, call SetCapability method.

High-Level:

$image\sqrblit.gif$ GetProperties and SetProperties methods allow the user to get and set a number of capabilities through the LTWAINPROPERTIES structure. If this structure does not have the capability needed to negotiate, user may use the low-level methods to do so.

To get each property set through an event, set EnableSetPropertiesEvent to TRUE and handle the OnSetPropertiesEvent Event.

$image\sqrblit.gif$ The QueryProperty method lets the user get the available values for a specific capability from the selected source, to free the ppltProperty parameter was allocated by calling the QueryProperty method call FreePropQueryStructure method.

When working with TW_CAPABILITY structures it may be necessary to create a container associated with that structure. For more information on containers, refer to How to Work with the Containers.