How to do a transparent splash screen using a 32 bits image png in linux

[dcelso]

Hello, to all.
I have a  png image to do a splash screen for my application. I would like do it using transparent options.
The basic code is do a form, put in alclient a timage and load into it the image 32bits png. After do it the image is correctly painted showing the background form color in his transparent pixels, and my idea is do that show the dekstop pixels instea of bacground from color.

In windows, using updatelayerdedwidows function, i can do it, the tweak used in delphi runs wells in lazarus windows version, I saw it in : http://melander.dk/articles/alphasplash/

But it does not run in lazarus linux version. Anyone have any idea?
Thanks to all.

[lainz]

Really you do that code works on Windows? You can show us the code? Thanks.

[dcelso]

Yes, if you do all steps put in the before link, you can optain gratifying results.
Resuming it is that I said.
Do a form, put in alclient a timage and load into it the image 32bits png. And use updatelayerdedwidows function in onshow method.

[lainz]

And where is UpdateLayeredWindow; I can't find WinAPI in Lazarus =D

[dcelso]

In user32.dll , please.  Read the link that i put before. It says the details better than me. Sorry, My esoEnglish is too poor.

[lainz]

In user32.dll , please.  Read the link that i put before. It says the details better than me. Sorry, My esoEnglish is too poor.

Ok my english maybe us poor too =) but also my programming, so if you get it already working please upload the project..

[dcelso]

Code: [Select]

unit Unit1;

{$mode objfpc}{$H+}

interface

uses
 {$IFDEF WINDOWS}
 windows,
 {$ENDIF}
 Classes,  SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls, FPimage;

type

  { TForm1 }

  TForm1 = class(TForm)
    Image1: TImage;
    procedure FormShow(Sender: TObject);
  private
    { private declarations }
  public
    procedure Execute;
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{$IFDEF WINDOWS}
function UpdateLayeredWindow(hwnd: HWND; hdcDst: HDC; pptDst: PPoint;
  psize: PSize; hdcSrc: HDC; pptSrc: PPoint; crKey: TColor;
  pblend: PBlendFunction; dwFlags: DWORD): BOOL; stdcall; external 'user32';
{$ENDIF}

{ TForm1 }

procedure TForm1.FormShow(Sender: TObject);
begin
  Image1.Picture.LoadFromFile('image.bmp');
  Execute;
end;

procedure TForm1.Execute;
var
   {$IFDEF WINDOWS}
   BlendFunction: TBlendFunction;
   BitmapSize: TSize;
   {$ENDIF}
   BitmapPos: TPoint;
   exStyle: DWORD;
 begin
   {$IFDEF WINDOWS}
   // Enable window layering
   exStyle := GetWindowLongA(Handle, GWL_EXSTYLE);
   if (exStyle and WS_EX_LAYERED = 0) then
     SetWindowLong(Handle, GWL_EXSTYLE, exStyle or WS_EX_LAYERED);
   {$ENDIF}


     // Resize form to fit bitmap
     ClientWidth := image1.picture.Bitmap.Width;
     ClientHeight := image1.picture.Bitmap.Height;

     // Position bitmap on form
     BitmapPos.x:=0;
     BitmapPos.y:=0;

     {$IFDEF WINDOWS}
     BitmapSize.cx := image1.picture.Bitmap.Width;
     BitmapSize.cy := image1.picture.Bitmap.Height;

     // Setup alpha blending parameters
     BlendFunction.BlendOp := AC_SRC_OVER;
     BlendFunction.BlendFlags := 0;
     BlendFunction.SourceConstantAlpha := 255;
     BlendFunction.AlphaFormat := AC_SRC_ALPHA;

     // ... and action!
     UpdateLayeredWindow(Handle, 0, nil, @BitmapSize, image1.picture.Bitmap.Canvas.Handle,
       @BitmapPos, 0, @BlendFunction, ULW_ALPHA);
     {$ENDIF}

end;


end.



Code: [Select]

[/object Form1: TForm1
  Left = 305
  Height = 240
  Top = 263
  Width = 320
  Caption = 'Form1'
  ClientHeight = 240
  ClientWidth = 320
  OnShow = FormShow
  LCLVersion = '1.1'
  object Image1: TImage
    Left = 0
    Height = 240
    Top = 0
    Width = 320
    Align = alClient
  end
end]