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Return bitmap

How to return tbitmap object form dll when I call function form my application?
0
mmaxim
Asked:
mmaxim
1 Solution
 
SteveWaiteCommented:
Do a search for madshi's dll example of hooking the keyboard. There you will see with memory mapped file to share memory so you can pass the bitmap from the dll. Look up CreateFileMapping() api.
0
 
DrDelphiCommented:
DLL:
library PicDLL;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }

uses
  SysUtils,
  Classes,
  Graphics;

{$R *.RES}

Function ShowMeThePic(picname:string):TBitmap;stdcall;
begin
  Result:=TBitmap.create;
  Result.LoadFromFile(Picname);
end;


Exports ShowMeThePic;

begin
end.
 





App:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Image1: TImage;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
 Function ShowMeThePic(picname:string):Tbitmap;stdcall;external 'picdll.dll';
{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
image1.picture.bitmap:=ShowMeThePic('mybmp.bmp');
end;

end.
0
 
ginsonicCommented:
Some time ago haved same problem . Thanks to Madshi for help:)

program YourProgram;

[...]

function DearDll_PleaseGiveMeABmp : dword; stdcall; external 'YourDll.dll';

procedure TForm1.Button1Click(Sender: TObject);
var bmp : TBitmap;
begin
 bmp := TBitmap.Create;
 bmp.Handle := DearDll_PleaseGiveMeABmp;
 Canvas.Draw(0, 0, bmp);
 bmp.Free;
end;

end.

library YourDll;

var GlobalBmp : TBitmap;

function DearDll_PleaseGiveMeABmp : dword; stdcall;
begin
 result := GlobalBmp.handle;
end;

exports DearDll_PleaseGiveMeABmp;

begin
 GlobalBmp := TBitmap.Create;
 GlobalBmp.LoadFromFile(...);
end.

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mmaximAuthor Commented:
That's it. Thanks for this clear example. Thanks DrDelphi, too...
0
 
ginsonicCommented:
Anytime with pleasure :)
0

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