Paint on TGPImage programmatically - delphi

Question

Could an TGPImage be loaded from PNG file or resource
himg := TGPImage.Create('heading.png');
and then be modified by painting on it like using canvas?
Or, better to say, I would like to paint a background using programmatic methods and then load an image from PNG above my painting in order to operate with this merged image as one solid TGPImage.
I looked at methods and properties of TGPImage and didn't find painting instruments.
Could I probably do this using TBitmap?
Following does not work:
_hbm := TBitmap.Create();
_hbm.Width := 1000;
_hbm.Height := 1000;
_hbm.Canvas.Brush.Color := clBlack;
_hbm.Canvas.Pen.Color := clBlack;
_hbm.Canvas.FillRect(Rect(0, 0, 1000, 1000));
_hgb := TGPBitmap.Create(_hbm.Handle);
....................
GPGraphics.DrawImage(_hgb, 0, 0, _hgb.GetWidth(), _hgb.GetHeight());

Answer 1

You don't need a TBitmap for that.
You simply need to use a TGPGraphics associated with the TGPImage to draw on the TGPImage surface.
Here is a very simple example:
uses GDIPOBJ, GDIPAPI, GDIPUTIL;
procedure TForm1.Button1Click(Sender: TObject);
var
b: TGPBitmap;
g: TGPGraphics;
pen: TGPPen;
encoderClsid: TGUID;
begin
b := TGPBitmap.Create('D:\in.png');
try
g := TGPGraphics.Create(b);
try
pen := TGPPen.Create(MakeColor(255, 255, 0), 3);
try
{ Draw a yellow Rectangle }
g.DrawRectangle(pen, MakeRect(0, 0, 200, 200));
GetEncoderClsid('image/png', encoderClsid);
b.Save('D:\out.png', encoderClsid);
finally
pen.Free;
end;
finally
g.Free;
end;
finally
b.Free;
end;
end;