Delphi Graphics32 resize layer in ImgView32

I want to be able to programatically resize one layer (the selected one) on click of a button. So basically I have an ImgView32, and I add layers to it. The last one is selected, then I want to press a button and onClick of that button I want the selected layer to be enlarged...

I want to be able to draw lines horizontal and vertical, in order to allow the user to draw the layout of a house (in 2D). But I want the user to be able to resize a line without the mouse... so he should be able to enter the width and height in editboxes and on click of a button apply the dimensions to the respective (selected) line.

How can I do that in graphics32?

I tried like this:

var
  orig,Tmp: TBitmap32;
  Transformation: TAffineTransformation;
begin
  Tmp := TBitmap32.Create;
  Orig := TBitmap32.Create;
  Transformation := TAffineTransformation.Create;

  if Selection is TBitmapLayer then
    begin
      orig := TBitmapLayer(Selection).Bitmap;
      try
          Transformation.BeginUpdate;
          Transformation.SrcRect := FloatRect(0, 0, orig.Width+200, orig.Height+200);
          Transformation.Translate(-0.5 * orig.Width, -0.5 * orig.Height);
          tmp.SetSize(200,200);
          Transformation.Translate(0.5 * Tmp.Width, 0.5 * Tmp.Height);
          Transformation.EndUpdate;
          orig.DrawMode := dmTransparent;
          Transform(Tmp, orig, Transformation);
          orig.Assign(Tmp);
          orig.DrawMode := dmTransparent;
      finally
        Transformation.Free;
        Tmp.Free;
      end;

    end;
end;

But the selected layer remains the same size and the contents shrink... I do not know what I am doing wrong. Please help.

Thank you

Solution

Something like:

begin
  if Selection is TBitmapLayer then
    begin
      TBitmapLayer(Selection).Location := FloatRect(TBitmapLayer(Selection).Location.Left,
        TBitmapLayer(Selection).Location.Top, TBitmapLayer(Selection).Location.Right + 200, TBitmapLayer(Selection).Location.Bottom + 200);    
    end;
end;

would make the layer wider by 200 pixel (in both x- and y- dimension). Doing so, the content will (typically) be stretched, if not specified otherwise.

The ugly assignment can be written more elegantly using a function like IncreaseRect(), which however is not present, but must be written by yourself.

It could look like:

function IncreaseRect(SourceRect: TFloatRect; IncX, IncY: TFloat): TFloatRect;
begin
  Result := FloatRect(SourceRect.Left, SourceRect.Top, 
    SourceRect.Right + IncX, SourceRect.Top + IncY);
end;

and called with

TBitmapLayer(Selection).Location := IncreaseRect(TBitmapLayer(Selection).Location, 200, 200);

Still I'm not sure if this is what you're after.