protected void TransferPictures()
{
// see http://www.twain.org/wp-content/uploads/2017/03/TWAIN-2.4-Specification.pdf
// page (3-20)
if (DataSource.SourceId.Id == 0)
{
return;
}
PendingXfers pendingTransfer = new PendingXfers();
TwainResult result;
try
{
do
{
pendingTransfer.Count = 0; // the Twain source will fill this in during DsPendingTransfer
IntPtr hbitmap = IntPtr.Zero;
// Get the image info
ImageInfo imageInfo = new ImageInfo();
result = Twain32Native.DsImageInfo(
ApplicationId,
DataSource.SourceId,
DataGroup.Image,
DataArgumentType.ImageInfo,
Message.Get,
imageInfo);
if (result != TwainResult.Success)
{
DataSource.Close();
break;
}
Bitmap bitmap;
try {
// Transfer the image from the device
result = Twain32Native.DsImageTransfer(
ApplicationId,
DataSource.SourceId,
DataGroup.Image,
DataArgumentType.ImageNativeXfer,
Message.Get,
ref hbitmap);
if (result != TwainResult.XferDone)
{
DataSource.Close();
break;
}
if (hbitmap == IntPtr.Zero)
{
throw new TwainException("Transfer complete, but bitmap pointer is still null.");
}
bitmap = BitmapRenderer.NewBitmapFromHBitmap(hbitmap);
} finally {
if (hbitmap != IntPtr.Zero)
{
Kernel32Native.GlobalFree(hbitmap);
hbitmap = IntPtr.Zero;
}
}
// End pending transfers
result = Twain32Native.DsPendingTransfer(
ApplicationId,
DataSource.SourceId,
DataGroup.Control,
DataArgumentType.PendingXfers,
Message.EndXfer,
pendingTransfer);
if (result != TwainResult.Success)
{
DataSource.Close();
break;
}
// fire the transfer event...
TransferImageEventArgs args = new TransferImageEventArgs(bitmap, pendingTransfer.Count != 0, 1.0f);
TransferImage(this, args);
if (!args.ContinueScanning)
{
break;
}
}while (pendingTransfer.Count != 0);
}
finally
{
// Reset any pending transfers
result = Twain32Native.DsPendingTransfer(
ApplicationId,
DataSource.SourceId,
DataGroup.Control,
DataArgumentType.PendingXfers,
Message.Reset,
pendingTransfer);
}
}
