PDF Viewer / Editor

Hi,

Hi Paul,

the problem is editing. So I say nothing about how to render.

With QP you may build PDFs or modify existing PDFs. But modifying is here only a drawing over. Generally it is very difficult to find out which part inside the PDF is for which visible part on screen. And modifying inside the PDF is no easy game.


So I did a small and dirty study to go another way. The idea is to build a PDF-page over a descriptionlist of objects. If we would have a such list, we could interpret it to build a PDF. If we want to correct something, we change the list and make a fresh PDF.

Because we store for our objects the coordinates, we may calc back (over the used scale for rendering) from mouseposition in image to coordinates and find out, on which object the mouse is pointing.

So we create a baseobject for all entries in our list.

Here is may source, but beware it is only a study, fare from use.

First the objects:

type
  TMyPaintObj = class(TObject) // the base for all kind of PDF-content
  private
    x0, y0,
    x1, y1: double;            // area, in which the object is to paint
  public
    procedure SetData(ax0, ay0, ax1, ay1: double); virtual;
    procedure Paint(QP: TQuickPDF); virtual; // only for inheritance
  end;

  TMyColorObj = class(TMyPaintObj)
  private
    C, M, Y, K: double;
  public
    procedure SetData(aC, aM, aY, aK: double); override;
    procedure Paint(QP: TQuickPDF); override;
  end;

  TMyLineObj = class(TMyPaintObj)
  private
  public
    procedure SetData(ax0, ay0, ax1, ay1: double); override;
    procedure Paint(QP: TQuickPDF); override;
  end;

  TMyBoxObj = class(TMyPaintObj)
  private
  public
    procedure SetData(ax0, ay0, ax1, ay1: double); override;
    procedure Paint(QP: TQuickPDF); override;
  end;

  TMyCircleObj = class(TMyPaintObj)
  private
    r1: double;
  public
    procedure SetRadius(ax0, ay0, ar1: double);
    procedure Paint(QP: TQuickPDF); override;
  end;

// our list-object, it represents all content
  TDrawList = class(TObjectList) // items = TMyPaintObj
    function GetMyPaintObj(aindex: integer): TMyPaintObj;
    procedure SetMyPaintObj(aindex: integer; const Value: TMyPaintObj);
  public
    ItemIndex: integer;
    property items[aindex: integer]: TMyPaintObj read GetMyPaintObj write SetMyPaintObj; default;
    constructor Create; virtual;
    destructor Destroy; override;
    procedure Paint(QP: TQuickPDF);
  end;


The implementation looks like this:


procedure TMyPaintObj.SetData(ax0, ay0, ax1, ay1: double);
begin
  x0 := ax0; y0 := ay0;
  x1 := ax1; y1 := ay1;
end;

procedure TMyPaintObj.Paint(QP: TQuickPDF); // only for inheritance
begin
end;

procedure TMyColorObj.SetData(aC, aM, aY, aK: double);
begin
  C := aC; M := aM; Y := aY; K := aK;
end;

procedure TMyColorObj.Paint(QP: TQuickPDF);
begin
  QP.SetLineColorCMYK(C, M, Y, K);
end;

procedure TMyLineObj.SetData(ax0, ay0, ax1, ay1: double);
begin
  inherited SetData(ax0, ay0, ax1, ay1);
end;

procedure TMyLineObj.Paint(QP: TQuickPDF);
begin
  QP.DrawLine(x0, y0, x1, y1);
end;

procedure TMyBoxObj.SetData(ax0, ay0, ax1, ay1: double);
begin
  inherited SetData(ax0, ay0, ax1, ay1);
end;

procedure TMyBoxObj.Paint(QP: TQuickPDF);
begin
  QP.DrawBox(x0, y0, x1-x0, y1-y0, 2);
end;

procedure TMyCircleObj.SetRadius(ax0, ay0, ar1: double);
begin
  inherited SetData(ax0, ay0, 0, 0);
  r1 := ar1;
end;

procedure TMyCircleObj.Paint(QP: TQuickPDF);
begin
  QP.DrawCircle(x0, y0, r1, 2);
end;

// in the same manner you have to construct more objects for fonts and text
// and all other things you need

constructor TDrawList.Create;
begin
  inherited Create;
  ItemIndex := -1;
end;

destructor TDrawList.Destroy;
begin
  inherited Destroy;
end;

function TDrawList.GetMyPaintObj(aindex: integer): TMyPaintObj;
begin
  if (aindex<0) or (aindex>=count)
  then Result := nil
  else Result := inherited Items[aindex] as TMyPaintObj;
end;

procedure TDrawList.SetMyPaintObj(aindex: integer; const Value: TMyPaintObj);
begin
  inherited Items[aindex] := Value;
end;

// this small code make our list to be a PDF-page
procedure TDrawList.Paint(QP: TQuickPDF);
var
  j: integer;
begin
  for j:=0 to Count-1
  do Items[j].Paint(QP); // every object paints itself
end;


If you did read till here, you know it looks as a lot of work, but it may be a way.


Cheers,
Werner

Hi Paul,

if you think about something in direction to RTF, so I advise you to a very nice open-source-program. It is made by Marek Jedlinski and named keynote. And there is a work based on it, called keynote-nf, made by Daniel Prado Velasko. The source is hosted at http://code.google.com/p/keynote-nf/ .

Inside this program works with RTF and images and a lot of other things are allowed too. May be it helps at building the big part outside PDF.


Cheers,

Werner