Graphics.GraphicExtension Function

Returns the default file-name extension of a graphics object.

Pascal

function GraphicExtension(GraphicClass: TGraphicClass): string;

C++

AnsiString GraphicExtension(TGraphicClass GraphicClass);

File

Graphics

Description

Call GraphicExtension to obtain a default extension value for the DefaultExt property of an Open, Open Picture, Save Picture or Save dialog. GraphicExtension returns the default extension for the type of graphics object specified by the GraphicClass parameter. In Delphi, the TGraphicClass type is the class type for descendants TGraphic.

These are the file extensions returned for each built-in graphics class:

Graphic class	File extension returned
TBitmap	bmp
TIcon	ico
TMetafile	emf

If custom graphics classes register a file extension, GraphicExtension will return that extension when passed the custom graphics class as an argument.

C++ Examples:

Copy Code

/*
The following example allows users to type the name of a
graphics class into an edit control and when a button is
pressed, the name of the default extension for that class is
displayed in another edit control.  In the form’s OnCreate
event handler (or a similar place) you must register the
graphics classes so that GetClass can find them.
*/
#include <memory>       //for STL auto_ptr class

TMetaClass *MetaClass;

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  std::auto_ptr<TClassFinder> myClassFinder(new TClassFinder(MetaClass, False));
  TGraphicClass mygraphclass = (TGraphicClass) (myClassFinder->GetClass(Edit2->Text));
//  TGraphicClass mygraphclass = (TGraphicClass) GetClass(Edit2->Text);
  Edit1->Text = GraphicExtension(mygraphclass);
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  MetaClass = __classid(TIcon); // ico
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(Graphics::TBitmap); // bmp
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TMetafile); // emf
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TShape);  // nographic extension
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TImage); // nographic extension
  RegisterClasses(&MetaClass, 0);
}

Copy Code

/*
This code displays a Save Picture dialog box with the
TBitmap default extension that is added automatically to
files that are given no extension. Confirm that the
bitmap file has been saved under the filename and path
specified.
*/
#include <memory>       //for STL auto_ptr class

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  AnsiString NewFileName, OldFileName;
  SavePictureDialog1->DefaultExt = GraphicExtension(__classid(Graphics::TBitmap));
  SavePictureDialog1->Filter = GraphicFilter(__classid(Graphics::TBitmap));
  OldFileName = "factory.bmp";
  if (SavePictureDialog1->Execute())
  {
    NewFileName = SavePictureDialog1->FileName;
    std::auto_ptr<TFileStream> OldFile(new TFileStream(OldFileName, (fmOpenRead | fmShareDenyWrite)));
    std::auto_ptr<TFileStream> NewFile(new TFileStream(NewFileName, (fmCreate | fmShareDenyRead)));
    NewFile->CopyFrom(OldFile.get(), OldFile->Size);
  };
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  Image1->Picture->LoadFromFile("../factory.bmp");
}

Delphi Examples:

Copy Code

{
The following example allows users to type the name of a
graphics class into an edit control and when a button is
pressed, the name of the default extension for that class is
displayed in another edit control.  In the form’s OnCreate
event handler (or a similar place) you must register the
graphics classes so that GetClass can find them.
}

uses ExtCtrls;

procedure TForm1.Button1Click(Sender: TObject);
var
  myClassFinder: TClassFinder;
  mygraphclass: TGraphicClass;
begin
  { make sure the classes are registered so that GetClass will work -- }
  { Usually, this goes in the initialization section where it is only executed once }
  RegisterClasses([TIcon, TBitmap, TButton, TShape, TImage, TMetafile]);
  try
    myClassFinder := TClassFinder.Create(TIcon, False);
    mygraphclass := TGraphicClass(myClassFinder.GetClass(Edit2.Text));
//    mygraphclass := TGraphicClass(GetClass(Edit2.Text));  // works as well
    Edit1.Text := GraphicExtension(mygraphclass);
  except
    on EAccessViolation do
      MessageDlg('Invalid class name.', mtError, [mbOK], 0)
  end;
end;

Copy Code

{
This code displays a Save Picture dialog box with the
TBitmap default extension that is added automatically to
files that are given no extension. Confirm that the
bitmap file has been saved under the filename and path
specified.
}
procedure TForm1.Button1Click(Sender: TObject);
var NewFileName, OldFileName: string;
    NewFile, OldFile: TFileStream;
begin
  SavePictureDialog1.DefaultExt := GraphicExtension(TBitmap);
  SavePictureDialog1.Filter := GraphicFilter(TBitmap);
  OldFileName := 'factory.bmp';
  if SavePictureDialog1.Execute then
  begin
    NewFileName := SavePictureDialog1.FileName;
    OldFile := TFileStream.Create(
      OldFileName, fmOpenRead or fmShareDenyWrite);
    try
      NewFile := TFileStream.Create(
        NewFileName, fmCreate or fmShareDenyRead);
      try
        NewFile.CopyFrom(OldFile, OldFile.Size);
      finally
        FreeAndNil(NewFile);
      end;
    finally
      FreeAndNil(OldFile);
    end;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Image1.Picture.LoadFromFile('factory.bmp');
end;