CAP_CAMERAENABLED

Description

This feature depends on “camera addressing”, which is the ability to address elements in the device responsible for the color space or location. TWAIN offers DAT_FILESYSTEM and CAP_CAMERASIDE to do this.

When set to TRUE the device will deliver images from the current camera. The Current Camera can be selected with either CAP_CAMERASIDE or DAT_FILESYSTEM. With CAP_CAMERASIDE it is possible to enable bottom (rear) only scanning, or have different settings for top and bottom. With DAT_FILESYSTEM it is possible to enter a Single Document Multiple Images (SDMI) mode in addition to enabling different settings for top and bottom.

Application

CAP_CAMERASIDE is easier to use, but cannot be used for SDMI. To enable bottom only scanning, set CAP_CAMERASIDE to TWCS_BOTTOM and set CAP_CAMERAENABLED to TRUE, then set CAP_CAMERASIDE to TWCS_TOP and set CAP_CAMERAENABLED to FALSE.

With DAT_FILESYSTEM an application can traverse and control all cameras individually.

An application should not use both CAP_CAMERASIDE and DAT_FILESYSTEM to address a camera.

Avoid using ICAP_PIXELTYPE after setting CAP_CAMERAENABLED. ICAP_PIXELTYPE implicitly sets CAP_CAMERAENABLED to TRUE for both sides of the current pixel type, and sets all other cameras to false. This supports legacy behavior. An application can always reasonably expect that setting ICAP_PIXELTYPE to TWPT_RGB and then scanning (simples or duplex) will result in getting color images.

The application is not allowed to turn off CAP_CAMERAENABLED for all cameras.

Source

A Source that supports CAP_CAMERAENABLED must support DAT_FILESYSTEM or CAP_CAMERASIDE or both.

If CAP_CAMERASIDE is supported, the application can use it to set the driver up for bottom (rear) only scanning. Set CAP_CAMERASIDE to TWCS_BOTTOM and set CAP_CAMERAENABLED to TRUE, then set CAP_CAMERASIDE to TWCS_TOP and set CAP_CAMERAENABLED to FALSE.

If DAT_FILESYSTEM is supported, then the application may be able to enter Single Document Multiple Images (SDMI) mode. In this mode the application can independently address the color, grayscale, bitonal, top and bottom cameras as supported by the driver. If the application sets CAP_CAMERAENABLED to TRUE for more than one “pixel type” on the same camera side, (for instance, color and bitonal on the front) then the driver will output multiple images for that side of the document.

When ICAP_PIXELTYPE is set or reset and CAP_CAMERASIDE is set to TWCS_BOTH, the source sets the current camera(s) to TRUE and sets all others to FALSE.

If the application attempts to set all CAP_CAMERAENABLED values to FALSE, the source returns a status of TWRC_FAILURE TWCC_CAPSEQERROR. At least one camera must be enabled at all times. Note: It is not recommended that applications mix the use of ICAP_PIXELTYPE with DAT_FILESYSTEM or CAP_CAMERASIDE. ICAP_PIXELTYPE is intended for simple applications that only want to choose color, grayscale or bitonal. Applications that want to provide bottom (rear) only scanning should use DAT_FILESYSTEM or CAP_CAMERASIDE. Applications that want to provide Single Document Multiple Images should use DAT_FILESYSTEM.

Values

Type: TW_BOOL

Value after MSG_OPENDS: (may be remembered from a previous session)

After MSG_RESET/MSG_RESETALL: (dependent on ICAP_PIXELTYPE)

Allowed Values: TRUE or FALSE

Containers

MSG_GET TW_ONEVALUE TW_ENUMERATION // 2.0 and higher

MSG_GETCURRENT TW_ONEVALUE

MSG_GETDEFAULT TW_ONEVALUE

MSG_SET TW_ONEVALUE

MSG_SETCONSTRAINT TW_ONEVALUE TW_ENUMERATION // 2.0 and higher

MSG_RESET TW_ONEVALUE

MSG_QUERYSUPPORT TW_ONEVALUE

Required By

None

TWAIN Version Introduced

Version 2.0

Related

CAP_CAMERAORDER CAP_CAMERASIDE