TOpenPictureDialog OS Depending ?
lazarus / 31-LCL

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BeanzMaster · 2020-07-22 15:05

Hi to all, i have a little question about TOpenPictureDialog.

I would like to improve the preview with my owns methods. (for
previewing images like pcx, tga, webp....)

I just simpy herited my own dialog from TOpenPictureDialog like that

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
TBZOpenPictureDialog = Class(TOpenPictureDialog)  private   
FPreviewFilename, FSaveTitle : string;  protected    procedure
UpdatePreview; override;  public    function Execute: boolean;
override;  end; implementation procedure
TBZOpenPictureDialog.UpdatePreview;var  CurFilename: string; 
FileIsValid: boolean;  Bmp : TBZBitmap;  NativeBmp :
Graphics.TBitmap; begin  CurFilename := FileName;   if CurFilename =
FPreviewFilename then exit;  FPreviewFilename := CurFilename; 
FileIsValid := FileExists(FPreviewFilename);
//FileIsReadable(FPreviewFilename);  if FileIsValid then  try    Bmp
:= TBZBitmap.create;    try      Bmp.LoadFromFile(FPreviewFilename); 
   PictureGroupBox.Caption := Format('(%s - %dx%d BPP:%d)',          
                     [Bmp.DataFormatDesc.Desc, Bmp.Width, Bmp.Height,
Bmp.ImageDescription.BitCount]);     
Bmp.Transformation.Stretch(ImageCtrl.ClientWidth,
ImageCtrl.ClientHeight, True);       NativeBmp := Bmp.ExportToBitmap; 
    ImageCtrl.Transparent := False;     
ImageCtrl.Picture.Bitmap.Assign(NativeBmp);      ImageCtrl.Repaint;  
   FreeAndNil(NativeBmp)     finally      FreeAndNil(Bmp)    end; 
except    FileIsValid := False;  end;  if not FileIsValid then  begin 
  ShowMessage('Not Valid');    ClearPreview;   end;end; function
TBZOpenPictureDialog.Execute: boolean;begin  Filter :=
GetBZImageFileFormats.BuildDialogFilters;  FSaveTitle :=  Self.Title; 
result := inherited Execute;end;           
But it's not working,

I'm on Windows.

So i suppose TOpenPictureDialog depend on the OS API
So, in this case,  my question What is the code for UpdatePreview ?
because the TGroupbox and Timage, is never show and didn't took in
account.

It is possible, without recreate the wheel ?

Thanks in advance

Cheers

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jamie · 2020-07-22 22:49

My docs say it's "PreviewFileControl" in the dialog is what you need
to paint on...

you may need to create a canvas for that..

 ACanvas.Handle := GetDC(PreviewFileCOntrol.Handle);

   now do your code..

Make sure you release the DC handle afterwards.

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BeanzMaster · 2020-07-23 07:36

Quote from: jamie on July 23, 2020, 12:49:24 amMy docs say it's
"PreviewFileControl" in the dialog is what you need to paint on...

you may need to create a canvas for that..

 ACanvas.Handle := GetDC(PreviewFileCOntrol.Handle);

   now do your code..

Make sure you release the DC handle afterwards.

Hi Jamie, thanks but i'm not understanding how do this, and why pass
through Handle.

Because TOpenPictureDialog is declared  as this :
The GroupBox and TImage are created and we can get access directly,
normally. 

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Type TOpenPictureDialog = class(TPreviewFileDialog)  private   
FDefaultFilter: string;    FImageCtrl: TImage;    FPictureGroupBox:
TGroupBox;    FPreviewFilename: string;  protected    class procedure
WSRegisterClass; override;    function  IsFilterStored: Boolean;
virtual;    property ImageCtrl: TImage read FImageCtrl;    property
PictureGroupBox: TGroupBox read FPictureGroupBox;    procedure
InitPreviewControl; override;    procedure ClearPreview; virtual;   
procedure UpdatePreview; virtual;  public    constructor
Create(TheOwner: TComponent); override;    procedure DoClose;
override;    procedure DoSelectionChange; override;    procedure
DoShow; override;    function GetFilterExt: String;    property
DefaultFilter: string read FDefaultFilter;  published    property
Filter stored IsFilterStored;  end;               
implementation constructor TOpenPictureDialog.Create(TheOwner:
TComponent);begin  inherited Create(TheOwner);  FDefaultFilter :=
GraphicFilter(TGraphic)+'|'+                     
 Format(rsAllFiles,[GetAllFilesMask, GetAllFilesMask,'']); 
Filter:=FDefaultFilter;   FPictureGroupBox:=TGroupBox.Create(Self); 
with FPictureGroupBox do begin    Name:='FPictureGroupBox';   
Align:=alClient;  end;   FImageCtrl:=TImage.Create(Self);  with
FImageCtrl do begin    Name:='FImageCtrl';   
Parent:=FPictureGroupBox;    Align:=alClient;    Center:=true;   
Proportional:=true;  end;end; procedure
TOpenPictureDialog.ClearPreview;begin 
FPictureGroupBox.Caption:='None'; 
FImageCtrl.Picture:=nil;end; procedure
TOpenPictureDialog.UpdatePreview;var  CurFilename: String; 
FileIsValid: boolean;begin  CurFilename := FileName;  if CurFilename =
FPreviewFilename then exit;   FPreviewFilename := CurFilename; 
FileIsValid := FileExistsUTF8(FPreviewFilename)                 and
(not DirPathExists(FPreviewFilename))                 and
FileIsReadable(FPreviewFilename);  if FileIsValid then    try     
FImageCtrl.Picture.LoadFromFile(FPreviewFilename);     
FPictureGroupBox.Caption := Format('(%dx%d)',       
[FImageCtrl.Picture.Width, FImageCtrl.Picture.Height]);    except    
FileIsValid := False;    end;  if not FileIsValid then   
ClearPreview;end;
So, i don't understand why my code doesn't work. And Why
TOpenPictureDialog 's code is like this and how it work ????
I need to declare/attach my own dialog somewhere or with a method that
i don't know, to the widgetset ???

Thanks

Cheers

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BeanzMaster · 2020-07-23 08:13

I have made little test, just by adding a form for previewing picture

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i typeunit
BZPictureDialogs; {$mode objfpc}{$H+} interface uses  Classes,
SysUtils, Graphics, GraphType, InterfaceBase, LCLType,  IntfGraphics,
FPimage, LCLIntf, LazFileUtils,  Forms, ExtDlgs , StdCtrls, ExtCtrls,
Dialogs,   BZGraphic, BZBitmap, BZBitmapIO;      {
TBZOpenPictureDialog }  TBZOpenPictureDialog =
Class(TOpenPictureDialog)  private    FPreviewFilename, FSaveTitle :
string;    FPreviewForm : TForm;  protected    procedure
UpdatePreview; override;  public    constructor Create(TheOwner:
TComponent); override;    procedure DoClose; override;    function
Execute: boolean; override;  end; implementation  procedure
TBZOpenPictureDialog.UpdatePreview;var  CurFilename: string; 
FileIsValid: boolean;  Bmp : TBZBitmap;  NativeBmp :
Graphics.TBitmap; begin   CurFilename := FileName;   if CurFilename =
FPreviewFilename then exit;  FPreviewFilename := CurFilename; 
FileIsValid := FileExists(FPreviewFilename);
//FileIsReadable(FPreviewFilename);  if FileIsValid then  try    Bmp
:= TBZBitmap.create;    try      Bmp.LoadFromFile(FPreviewFilename); 
   PictureGroupBox.Caption := Format('(%s - %dx%d BPP:%d)',          
                     [Bmp.DataFormatDesc.Desc, Bmp.Width, Bmp.Height,
Bmp.ImageDescription.BitCount]);     
Bmp.Transformation.Stretch(ImageCtrl.ClientWidth,
ImageCtrl.ClientHeight, True);       NativeBmp := Bmp.ExportToBitmap; 
    ImageCtrl.Transparent := False;     
ImageCtrl.Picture.Bitmap.Assign(NativeBmp);      ImageCtrl.Repaint;  
   FPreviewForm.Caption := FSaveTitle + ' - ' +
ExtractFileName(FPreviewFilename) + ' : ' + PictureGroupBox.Caption; 
   FPreviewForm.Show;      bmp.DrawToCanvas(FPreviewForm.Canvas,
FPreviewForm.ClientRect);       FreeAndNil(NativeBmp)     finally    
FreeAndNil(Bmp)    end;  except    FileIsValid := False;  end;  if not
FileIsValid then  begin    ShowMessage('Not Valid');   
FPreviewForm.Close;    ClearPreview;   end;end; function
TBZOpenPictureDialog.Execute: boolean;begin  Filter :=
GetBZImageFileFormats.BuildDialogFilters;  FSaveTitle :=  Self.Title; 
result := inherited Execute;end; constructor
TBZOpenPictureDialog.Create(TheOwner: TComponent);begin  inherited
Create(TheOwner);  FPreviewForm := TForm.Create(nil); 
FPreviewForm.Width := 320;  FPreviewForm.Height := 240; 
FPreviewForm.Position :=  poScreenCenter; end; procedure
TBZOpenPictureDialog.DoClose;begin  FPreviewForm.Close; 
FreeAndNil(FPreviewForm);  inherited DoClose;end;         

It work, picture are showing Like we see on the attached GIF.
It seems  "ImageCtrl" is not used because it have the default
dimensions 60x60 and the preview in dialog itself is not shown.

Thanks in advance for your help

Cheers

Jérôme