Graphical Progress Bar for Delphi applications - Partial / Continuous Move

Display a continuous bar by "moving" a graphical object

When your application performs a time-consuming operation, you can use a progress bar, the TProgressBar Delphi control, to show how much of the task is completed.

When you do not know how many steps are needed for a progress bar - you might want to display a continuous bar - or a moving graphical object. The UpdateImageProgress takes a reference to a TImage control displaying a picture. By calling the procedure from inside, for example, a timer event (TTimer control), a graphical progress effect is achieved.

The UpdateImageProgress shifts the image to the right - using the boundaries of the image - thus creating a continuous progress bar.

//"moves" image to the right in "step" steps
procedure UpdateImageProgress(const img : TImage) ;
const
  step = 4;
var
  b : TBitmap;
begin
  with img.Picture.Bitmap do
  begin
    b := TBitmap.Create;
    try
      b.Width := Width;
      b.Height := Height;
      BitBlt(b.Canvas.Handle, step, 0, Width-step, Height, Canvas.Handle, 0, 0, SRCCOPY) ;
      BitBlt(b.Canvas.Handle, 0, 0, step, Height, Canvas.Handle, Width-step, 0, SRCCOPY) ;
      Assign(b) ;
    finally
      FreeAndNil(b) ;
    end;
  end;
end;

UpdateImageProgress shifts the trailing "step" part of the bitmap to the front, moving the rest along.

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