TPicture.LoadFromFile not working
lazarus / 39-Graphics

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lainz · 2010-09-11 22:14

Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
ExtCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
    Image1: TImage;
    procedure Image1MouseEnter(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;
  picture1: TPicture;
  bitmap1: TBitmap;

implementation

{$R *.lfm}

{ TForm1 }

procedure TForm1.Image1MouseEnter(Sender: TObject);
begin
  Image1.Picture:=picture1;
end;

initialization

picture1.Create;
picture1.LoadFromFile('1.bmp');

end.
Error: External SIGSEGV; and load "picture.inc" at line 730 "
NewGraphic.OnProgress := @Progress;"

also the same error on bitmap.LoadFromFile

What i'm doing wrong?

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jhvhs · 2010-09-12 07:35

This should do the trick:
Code: [Select]procedure TForm1.Image1MouseEnter(Sender: TObject);
begin
  Image1.Picture.Assign(picture1);
end;
...
Picture1 := TPicture.Create;

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theo · 2010-09-12 09:23

It doesn't have to do with Picture but with the way you're creating
objects.

picture1.Create;
Should be:
picture1:=TPicture.create;

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lainz · 2010-09-12 14:27

Thanks! Now i have an image button with 3 pictures (normal, mouse
over, mouse down)

Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
ExtCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
    Image1: TImage;
    procedure Image1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Image1MouseEnter(Sender: TObject);
    procedure Image1MouseLeave(Sender: TObject);
    procedure Image1MouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;
  picture1: TPicture;
  picture2: TPicture;
  picture3: TPicture;

implementation

{$R *.lfm}

{ TForm1 }

procedure TForm1.Image1MouseEnter(Sender: TObject);
begin
  Image1.Picture.Assign(picture2);
end;

procedure TForm1.Image1MouseDown(Sender: TObject; Button:
TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Image1.Picture.Assign(picture3);
end;

procedure TForm1.Image1MouseLeave(Sender: TObject);
begin
  Image1.Picture.Assign(picture1);
end;

procedure TForm1.Image1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Image1.Picture.Assign(picture2);
end;

initialization

{normal}
picture1:=TPicture.Create;
picture1.LoadFromFile('1.png');

{mouse over}
picture2:=TPicture.Create;
picture2.LoadFromFile('2.png');

{mouse down}
picture3:=TPicture.Create;
picture3.LoadFromFile('3.png');

end.

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wotanica · 2010-09-21 13:36

Not to sound harsh but you should be carefull where you create
objects. I for one would not setup picture-objects during unit
initialization (unless they are global and have proper access
methods). You are bound to get access violation errors sooner or
later. If the pictures are part of a form, or being used by a
component, you should keep them within the scope of that parent rather
than on unit level:

Code: [Select](* override constructor *)
Constructor TForm1.Create(AOwner:TComponent);
Begin
  Inherited Create(AOwner);
  FPicture1:=TPicture.Create(NIL);
  (.. etc ..)
end;

Destructor TForm1.Destroy;
Begin
  if assigned(FPicture1) then
  FreeAndNIL(FPicture1);
  Inherited;
end;

The reason this is better is twofold:
1. You dont have to look for bizare errors outside the class (if
something goes wrong with "picture1" the exception might turn up
inside a form method, but it's actually on unit level. Better to keep
these things seperated).
2. You have little control over how lazarus unloads units. If you
initialize pictures this way - you at least have to take height of
application.termination.

Just a friendly heads up, you are going to experience problems if you
go down that road of programming.