Setting the TWAIN Image Acquisition Mode

For those who are unfamiliar with the three types of TWAIN acquisition, the following is a synopsis of each:

Native: ImageGear loads the entire image into an IGPage Object as one continuous data stream.
Disk File Transfer: The data source saves the acquired image directly into a file. Images acquired by this method cannot be automatically displayed during scanning because they are not loaded into memory. ImageGear allows you the added control of setting the filename and file format to be used.
Buffered Memory Transfer: The data will be loaded into an IGPage Object (as for Native Transfer), except that it will be buffered and stored in either strips or tiles. ImageGear also allows you to set the buffer size.

Not all of the TWAIN-supported transfer syntax modes are supported by all Data Sources. If you try to use an acquisition mode that your device does not support, you will receive an error message.

To set the transfer syntax to Disk File Transfer:

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Dim capOneValue As IGTWAINCapOneValue Set capOneValue = frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE) capOneValue.ID = IG_TW_ICAP_XFERMECH capOneValue.ItemType = AM_TID_META_UINT16 capOneValue.Value.ChangeType IG_DATA_LONG capOneValue.Value.Long = IG_TW_SX_FILE frmMain.IGTwainCtl1.SetCapability capOneValue, IG_TW_MSG_SET

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Dim capOneValue As IGTWAINCapOneValue
Set capOneValue =
frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE)
capOneValue.ID = IG_TW_ICAP_XFERMECH
capOneValue.ItemType = AM_TID_META_UINT16
capOneValue.Value.ChangeType IG_DATA_LONG
capOneValue.Value.Long = IG_TW_SX_FILE
frmMain.IGTwainCtl1.SetCapability capOneValue, IG_TW_MSG_SET

To set the transfer syntax to Buffered Memory:

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Dim capOneValue As IGTWAINCapOneValue Set capOneValue = frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE) capOneValue.ID = IG_TW_ICAP_XFERMECH capOneValue.ItemType = AM_TID_META_UINT16 capOneValue.Value.ChangeType IG_DATA_LONG capOneValue.Value.Long = IG_TW_SX_MEMORY frmMain.IGTwainCtl1.SetCapability capOneValue, IG_TW_MSG_SET

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Dim capOneValue As IGTWAINCapOneValue
Set capOneValue =
frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE)
capOneValue.ID = IG_TW_ICAP_XFERMECH
capOneValue.ItemType = AM_TID_META_UINT16
capOneValue.Value.ChangeType IG_DATA_LONG
capOneValue.Value.Long = IG_TW_SX_MEMORY
frmMain.IGTwainCtl1.SetCapability capOneValue, IG_TW_MSG_SET

To set the transfer syntax to Native:

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Dim capOneValue As IGTWAINCapOneValue Set capOneValue = frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE) capOneValue.ID = IG_TW_ICAP_XFERMECH capOneValue.ItemType = AM_TID_META_UINT16 capOneValue.Value.ChangeType IG_DATA_LONG capOneValue.Value.Long = IG_TW_SX_NATIVE frmMain.IGTwainCtl1.SetCapability capOneValue, IG_TW_MSG_SET

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Dim capOneValue As IGTWAINCapOneValue
Set capOneValue =
frmMain.IGTwainCtl1.CreateCapability(IG_TW_ON_ONEVALUE)
capOneValue.ID = IG_TW_ICAP_XFERMECH
capOneValue.ItemType = AM_TID_META_UINT16
capOneValue.Value.ChangeType IG_DATA_LONG
capOneValue.Value.Long = IG_TW_SX_NATIVE
frmMain.IGTwainCtl1.SetCapability capOneValue,
IG_TW_MSG_SET

By default, if no call is made to set transfer mode, ImageGear will use the mode set in Data Source.