[[Caral]]

Hola
Dibujando encima de un TImage lineas rectas, tambien se pueden hacer otras figuras.

Código Delphi [-]
unit Unit1;

interface

uses
  SysUtils, Windows, Messages, Classes, Graphics, Controls, Forms, Dialogs,
  Buttons, ExtCtrls, StdCtrls, ComCtrls, Menus;

type
  TDrawingTool = (dtLine, dtRectangle, dtEllipse, dtRoundRect);
  TForm1 = class(TForm)
    Image1: TImage;
    BitBtn1: TBitBtn;
    BitBtn2: TBitBtn;
    procedure Image1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Image1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure Image1MouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
    BrushStyle: TBrushStyle;
    PenStyle: TPenStyle;
    PenWide: Integer;
    Drawing: Boolean;
    Origin, MovePt: TPoint;
    DrawingTool: TDrawingTool;
    CurrentFile: string;
    procedure DrawShape(TopLeft, BottomRight: TPoint; AMode: TPenMode);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  AnteriorBkMode: integer;
begin
  Drawing := True;
  Image1.Canvas.MoveTo(X, Y);
  Origin := Point(X, Y);
  MovePt := Origin;
 with Image1.Canvas do begin
  Brush.Color := clBlack;
  AnteriorBkMode := SetBkMode(Handle, TRANSPARENT);
  SetBkMode(Handle, AnteriorBkMode);
end;

end;

procedure TForm1.Image1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
   if Drawing then
  begin
    DrawShape(Origin, MovePt, pmNotXor);
    MovePt := Point(X, Y);
    DrawShape(Origin, MovePt, pmNotXor);
  end;
end;


procedure TForm1.DrawShape(TopLeft, BottomRight: TPoint; AMode: TPenMode);
begin
  with Image1.Canvas do
  begin
    Pen.Mode := AMode;
    case DrawingTool of
      dtLine:
        begin
          Image1.Canvas.MoveTo(TopLeft.X, TopLeft.Y);
          Image1.Canvas.LineTo(BottomRight.X, BottomRight.Y);
        end;
      dtRectangle: Image1.Canvas.Rectangle(TopLeft.X, TopLeft.Y, BottomRight.X,
        BottomRight.Y);
      dtEllipse: Image1.Canvas.Ellipse(Topleft.X, TopLeft.Y, BottomRight.X,
        BottomRight.Y);
      dtRoundRect: Image1.Canvas.RoundRect(TopLeft.X, TopLeft.Y, BottomRight.X,
        BottomRight.Y, (TopLeft.X - BottomRight.X) div 2,
        (TopLeft.Y - BottomRight.Y) div 2);
    end;
  end;
end;


procedure TForm1.Image1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
    if Drawing then
  begin
    DrawShape(Origin, Point(X, Y), pmCopy);
    Drawing := False;
  end;
end;

end.

Saludos