TBitmap.FreeImage Method

Frees the cached file image stored in memory by the bitmap.

Pascal

procedure FreeImage;

C++

__fastcall FreeImage();

Description

Use FreeImage to reduce the memory requirements of an application when color depth and pixel format are not an issue. Freeing the image releases the memory allocated for the bitmap image when it was originally loaded to disk. Consequently, some of the original pixel format of the bitmap is lost (for example, if you changed its format to a DIB) as well as the color depth of the bitmap.

When a bitmap is loaded into a bitmap object, the bitmap object creates an image of the loaded bitmap in memory. If the bitmap isn't changed, the memory image is used when saving the bitmap, to verify that the bitmap has not lost color depth or changed the pixel format.

C++ Examples:

Copy Code

/*
This example uses a button on a form and creates two bitmaps
dynamically.  One bitmap is monchrome, which means all
non-white colors become black.  The bitmap file path is
relative to the Debug directory.
Note: For the C++ Builder, capitalization matters for the file
name and path.
*/

#include <memory>       //for STL auto_ptr class

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  std::auto_ptr<Graphics::TBitmap> Bitmap1(new Graphics::TBitmap());
  std::auto_ptr<Graphics::TBitmap> Bitmap2(new Graphics::TBitmap());
  try
  {
    Bitmap1->LoadFromFile("..\\FACTORY.BMP");
    Bitmap2->Assign(Bitmap1.get());     // Copy Bitmap1 into Bitmap2
    Bitmap2->Dormant();           // Free up GDI resources
    Bitmap2->FreeImage();         // Free up Memory.
    Canvas->Draw(20, 20, Bitmap2.get());  // Note that previous calls don't lose the image
    Bitmap2->Monochrome = true;
    Canvas->Draw(80, 80, Bitmap2.get());
    Bitmap2->ReleaseHandle();       // This will actually lose the bitmap;
  }
  catch (...)
  {
    MessageBeep(0);
  }
}

Delphi Examples:

Copy Code

{
This example uses a button on a form and creates two bitmaps
dynamically.  One bitmap is monchrome, which means all
non-white colors become black.  The bitmap file path is
relative to the Debug directory.
}
procedure TForm1.Button1Click(Sender: TObject);
var
 BitMap1,BitMap2 : TBitMap;
 MyFormat : Word;
begin
   BitMap2 := TBitMap.Create;
   BitMap1 := TBitMap.Create;
try
   BitMap1.LoadFromFile('factory.bmp');
   BitMap2.Assign(BitMap1);     // Copy BitMap1 into BitMap2
   BitMap2.Dormant;             // Free up GDI resources
   BitMap2.FreeImage;           // Free up Memory.
   Canvas.Draw(20,20,BitMap2);  // Note that previous calls don't lose the image
   BitMap2.Monochrome := true;
   Canvas.Draw(80,80,BitMap2);
   BitMap2.ReleaseHandle;       // This will actually lose the bitmap;
 finally
   BitMap1.Free;
   BitMap2.Free;
 end;
end;

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