The twexplore program is available either to run as a script from the Python interpreter or as an executable. The executable does not require a Python system to run.
On loading the program, a form is displayed, as show above. The form has a menubar, from which all the options are taken, a main pane, which will show the source capabilities when you connect to the source, and a status bar. The status bar has three sections, showing the latest message, the name of the current source and the current state in the TWAIN state concept.
To open a source, select menu->connect. If you have twain source on your PC, you should see an option list. Select the driver you are interested in. Once a driver is selected, the source information is displayed in a dialogue. The TWAIN specification contains information on the meaning of the source information.
Once the source is open, the source capabilities are displayed on the main form. Where the attempt to read a capability produced an exception, the exception is displayed instead of the value. The 'Supported Values' column shows the result of the GetCapability() operation. This value types can be seen clearly. The highlighted item (ICAP_PIXELTYPE) displays its capabilties using an enumerator. The 'Current Value' column shows that the current value is 2 (from the specification page 336, 2=TWPT_RGB).
Under the TWAIN specification, the data source can give our program the list of supported capabilities (CAP_SUPPORTEDCAPS). The supported capabilities are shows in green.
By double clicking on a capability a capability editing dialog is show. This dialog allows you to attempt to set the capability to an arbitrary value. You enter the value in the dialog box and select the type from the radio-box. Where the capability can be retrieved, the dialog is initialised to the current value of the capability and the type returned by the GetCapabilityCurrent() request.
The value field is interpreted in the context of the twain module. You can therefore use both values (e.g. 0) and constants (e.g. TWPT_RGB). The log message is translated back to the symbolic constant.
You can reset a capability to the default value using the 'Reset Value' button. After you have changed a capability, you can use the menu option 'File->Refresh Capabilities' to refresh the main display.
To request an image from the TWAIN device, select the menu option 'File->Acquire'. You are given the option of displaying the TWAIN source user interface. If you do not use the twain source user interface, you can use the Layout dialog to select a frame from the image.
When the image is available on the Data Source, our application is notified via a callback and the transfer dialog is displayed. This dialog shows the information which is available about the image. The twain module supports two options for transfer of the image 'Transfer Natively', or 'Transfer to File'. If you select 'Transfer Natively', the image is displayed in a simple frame. If you select transfer to file, you will be prompted for a filename and file type. If there are no more images remaining on the Data Source, the Transfer dialog is closed.