Acquiring an Image (Delphi 4.0)

Take the following steps to start a project and to add some code that acquires an image from a TWAIN source:

1.	Start Delphi 4.0.
2.	If you didn’t install LEAD RasterView Control, install it as follows:
	On the Component pull-down menu, use the Import ActiveX Control… and select the LEAD RasterView Control (14.5). Press install, and then compile and install the package dclusr40.dpk.
3.	Select the LEAD RasterView control and add it to Form1. Size and position the control as you want it to appear at run time.
4.	On the Project pull-down menu, use the Import Type library… and select the LEAD RasterTwain Object Library (14.5). Press OK.
5.	If you didn’t import LEAD Raster Variant before, import it as follows:
6.	On the Project pull-down menu, use the Import Type library… and select the LEAD Raster Variant Object Library (14.5). Press install, and then compile and install the package dclusr40.dpk.
7.	If you didn’t install LEADEventSink Control, install it as follows:
	On the Component pull-down menu, use Install component …, and browse to LEADXX\Include\LEvntSnk.pas. Press OK, and then compile and install the package dclusr40.dpk.
8.	From the ActiveX controls, add the LEADEventSink control to Form1.
9.	Add the following code to the private section of Unit1:

TwainCap: LEADTwainCapability;
RasterTwain: LEADRasterTwain;
nXferMode: Integer;
nRet: Integer;
Function TwainSetCapability ( uCapability: Integer; CapVal: LEADRasterVariant; uItemType: Integer): Integer;

10.	Handle the Form1 OnCreate event, and code the FormCreate procedure as follows:

procedure TForm1.FormCreate(Sender: TObject);
begin
   TwainCap:= CreateComObject ( CLASS_LEADTwainCapability ) as LEADTwainCapability;

   RasterTwain:= CreateComObject ( CLASS_LEADRasterTwain ) as LEADRasterTwain;
   RasterTwain.InitSession ( Handle ) ;
   LEADEventSink1.Connect  ( RasterTwain, _LEADRasterTwainEvents );
end;

11.	Handle the Form1 OnClose event, and code the FormClose procedure as follows:

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
RasterTwain.EndSession();
end;

12.	At the top of Form1, add six Buttons and three Option Buttons and name them as follows:
	Name	Caption
	btnOK	OK
	btnCancel	Cancel
	btnAcquire	Acquire
	btnSelectSource	Select Source
	btnNative	Native
	btnMemBuf	Memory Buffered
	btnFile	File
	btnSaveTemplate	Save Template File
	btnLoadTemplate	Load Template File
13.	Handle the btnOK OnClick event, and code the btnOKClick procedure as follows. In online help, you can use the Edit pull-down menu to copy the block of code.

procedure TForm1.btnOKClick(Sender: TObject);
begin
Close ( ) ;
end;

14.	Handle the btnCancel OnClick event, and code the btnCancelClick procedure as follows. In online help, you can use the Edit pull-down menu to copy the block of code:

procedure TForm1.btnCancelClick(Sender: TObject);
begin
Close ( ) ;
end;

15.	Handle the btnAcquire OnClick event, and code the btnAcquireClick procedure as follows:

procedure TForm1.btnAcquireClick(Sender: TObject);
begin
RasterTwain.Acquire ( L_LTWAIN_SHOW_USER_INTERFACE ) ;
end;

16.	Handle the btnSelectSource OnClick event, and code the btnSelectSourceClick procedure as follows:

procedure TForm1.btnSelectSourceClick(Sender: TObject);
begin
RasterTwain.SelectSource ( ) ;
end;

17.	Handle the btnSaveTemplate OnClick event, and code the btnSaveTemplateClick procedure as follows:

procedure TForm1.btnSaveTemplateClick(Sender: TObject);
begin
nRet:= RasterTwain.SaveTemplate ('c:\test.ltt');
end;

18.	Handle the btnLoadTemplate OnClick event, and code the btnLoadTemplateClick procedure as follows:

procedure TForm1.btnLoadTemplateClick(Sender: TObject);
begin
nRet:= RasterTwain.LoadTemplate ( 'c:\test.ltt' ) ;
end;

19.	Handle the btnNative option button’s OnClick event, and code the btnNativeClick procedure as Follows:

procedure TForm1.btnNativeClick(Sender: TObject);
var
   CapVal: LEADRasterVariant;
begin
   nXferMode:= L_TWSX_NATIVE;
CapVal:= coLEADRasterVariant.Create ( );
CapVal.Type_:= VALUE_USHORT;
   CapVal.LongValue:= nXferMode;
   TwainSetCapability ( L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16 );
end;

20.	Handle the btnMemBuf option button’s OnClick event, and code the btnMemBufClick procedure as follows:

procedure TForm1.btnMemBufClick(Sender: TObject);
var
   CapVal: LEADRasterVariant;
begin
   nXferMode:= L_TWSX_MEMORY;
CapVal:= coLEADRasterVariant.Create ( );
   CapVal.Type_:= VALUE_USHORT;
   CapVal.LongValue:= nXferMode;
   TwainSetCapability ( L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16 );
end;

21.	Handle the btnFile option button’s OnClick event, and code the btnFileClick procedure as follows:

procedure TForm1.btnFileClick(Sender: TObject);
var
   CapVal: LEADRasterVariant;
begin
   nXferMode:= L_TWSX_FILE;
CapVal:= coLEADRasterVariant.Create ( );
   CapVal.Type_:= VALUE_USHORT;
   CapVal.LongValue:= nXferMode;
   TwainSetCapability ( L_ICAP_XFERMECH, CapVal, L_TWTY_UINT16 );
   RasterTwain.FileTransferName:= 'c:\twain.bmp';
end;

22.	Handle the LEADEventSink1 OnInvoke event, and code the LEADEventSink1Invoke procedure as follows:

procedure TForm1.LEADEventSink1Invoke(Sender: TObject; DispID: Integer;
  const IID: TGUID; LocaleID: Integer; Flags: Word; Params: tagDISPPARAMS;
  varResult, ExcepInfo, ArgErr: Pointer);
var
   pBitmap: Integer;
begin
   Case (DispID) of
      LEADRASTER_TWAIN_EVENTS_ACQUIREPAGEEVENT:
      begin
         pBitmap:= OleVariant ( Params.rgvarg[0] ) ;
         ShowMessage ( 'Acquisition of Image Done' ) ;
         LEADRasterView1.Raster.InsertBitmapListItem ( -1, pBitmap ) ;
      end;
   end;
end;

23.	Add the TwainSetCapability function body to the Unit1 file.

Function TForm1.TwainSetCapability ( uCapability: Integer; CapVal: LEADRasterVariant; uItemType: Integer): Integer;
var
   iRet: Integer;
begin
   TwainCap.EnableMethodErrors:= False;
   TwainCap.CapInfo.Capability:= uCapability;
   TwainCap.CapInfo.ConType:= L_TWON_ONEVALUE;
   TwainCap.CapOneValue.OneValItemType:= uItemType;
   TwainCap.CapOneValue.OneValCapValue:= CapVal;

   iRet:= RasterTwain.SetCapability2(TwainCap, L_LTWAIN_CAPABILITY_SET);
   TwainSetCapability:= iRet;
end;

24.	At the beginning of the Unit1 file, add ComObj, LTRASTERVARIANTLib_TLB, LTRASTERTWAINLib_TLB, ActiveX to the uses section. This lets you handle the Com objects, the Raster Twain object library, and use ActiveX Controls.
25.	Run your program to test it.