TAdvPDFLib can I access the canvas

VCL TMS VCL UI Pack
1

Hi, with TAdvPDFLib is it possible to directly access the PDF canvas, i.e. a TCanvas object? We want to draw some high resolution images (e.g. 10000x10000 pixels) and get out of memory errors if we have to first draw this to a bitmap. Thx.

2

Unfortunately there is no TCanvas and right now, the bitmap drawing goes through a TBitmap object. It's not possible to add bitmap data directly from a stream, we would need to add support for that. Which TCanvas capabilities do you need exactly?

3

Well most of them, we have some fairly complex plotting code. In the PDF we want to see exactly the same thing as we have drawn onto a TImage on a form, but we want it to be higher resolution in the PDF. So we can't just take a screengrab, we need to do all the canvas based drawing again on the PDF.

So we would require at least the following:
Pen
Brush
Font
MoveTo
LineTo
TextOut
Ellipse
Arc
Polygon
Polyline
Rectangle
FillRect

Thx.

4

If you have the drawing calls to a TCanvas, which you are using to create the bitmap you could map them onto TAdvGraphics. We have created a special descendant engine that you can use together with the PDF engine to create more complex graphics. Here is an example.

uses
  Math, AdvTypes, Types, AdvPDFLib, AdvGraphicsTypes, AdvGraphicsPDFEngine;

procedure TForm12.Button1Click(Sender: TObject);
var
  p: TAdvPDFLib;
  pg: TAdvGraphicsPDFEngine;
  pth: TAdvGraphicsPath;
  r: TRectF;
  st, swp: Single;
  cp, rd, sp, ird: TPointF;
begin
  p := TAdvPDFLib.Create;
  pg := TAdvGraphicsPDFEngine.Create(p);
  pth := TAdvGraphicsPath.Create;
  try
    p.BeginDocument('test.pdf');
    p.NewPage;

    pg.Fill.Color := gcRed;
    pg.Fill.Kind := gfkGradient;
    pg.Fill.ColorTo := gcOrange;
    pg.Stroke.Kind := gskSolid;
    pg.Stroke.Color := gcDarkred;

    r := RectF(200, 200, 500, 500);

    st := 90;
    swp := 180;

    rd := PointF((r.Right - r.Left) / 2, (r.Bottom - r.Top) / 2);
    ird := PointF((r.Right - r.Left) / 4, (r.Bottom - r.Top) / 4);
    cp := CenterPointEx(r);
    sp.X := cp.X + ird.X * Cos(DegToRad(st));
    sp.Y := cp.Y + ird.Y * Sin(DegToRad(st));

    pth.Clear;
    pth.MoveTo(sp);
    pth.AddArc(cp, rd, st, swp);
    pth.AddArc(cp, ird, st + swp, -swp);
    pth.ClosePath;

    pg.DrawPath(pth);

    p.EndDocument(True);
  finally
    pth.Free;
    pg.Free;
    p.Free;
  end;
end;
5

Ok thx we'll have a look into that.