Bitmap Editing with paint box

I try to ad a basic bmp (or Icon) editing feature into my app. So I am testing around with a paintbox.
I plan to load an image, convert to bmp, edit it in the paint box, convert back and save.

I guess, this will be a way, but it takes a while. Especially since I want to draw "blockwise" (zooming into the bmp and simulating big pixels). Maybe I should use a DrawGrid instead?

Beside this, there are many issues need to be resolved like drawing this frames while moving the mouse, undo (should I save old bmps etc, or drawing vectors like described in mastering delphi?);

Hence I look forward to acomplish this. I want to know whether this is the right approach before dwelling deep into this stuff. Maybe sombody has finished code for such a thing.

I would give more points for a finalized solution. The 125 points are meant for input which really helps me further.


I have created my first simple example on this topic:

(* Unit ================================*)

unit BMPEditU;

interface

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

type
  TForm1 = class(TForm)
    PaintBox1: TPaintBox;
    Button1: TButton;
    Panel1: TPanel;
    CD: TColorDialog;
    rgZoom: TRadioGroup;
    RGTool: TRadioGroup;
    procedure Button1Click(Sender: TObject);
    procedure PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Panel1Click(Sender: TObject);
    procedure rgZoomClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure PaintBox1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure PaintBox1MouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
    Zoom:integer;
    XD,YD,XU,YU:Integer;
    BM:TBitmap;
    procedure DrawPixes(x, y: integer; col: TColor);
    procedure DrawLine(xS, YS, xE, yE, size: integer; Col: TColor);
    procedure DrawCircle(xS,YS,xE,yE,size:integer; Col:TColor);
    procedure DrawBox(xS, YS, xE, yE, size: integer; Col: TColor);
    procedure Flood(xS, YS: integer; Col: TColor);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
 

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
BM.LoadFromFile('D:\My Documents\My Programs\Glyphs\ACCOUNT.BMP');
PaintBox1.canvas.Draw(0,0,bm);

end;

procedure TForm1.PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
XD:=X;YD:=Y;

   
end;


procedure TForm1.DrawPixes(x,y:integer;col:TColor);
  var i,j,x1,y1:integer;
begin
if (zoom > 0) AND (BM<>nil) then
begin
x1:=x div zoom * zoom;
y1:=y div zoom * zoom;

for i:= 1 to zoom do
for j:= 1 to zoom do
paintbox1.Canvas.Pixels[x1+i,y1+j]:=col;
end;
end;



procedure TForm1.Panel1Click(Sender: TObject);
begin
cd.execute;
panel1.Color:=cd.Color;
end;

procedure TForm1.rgZoomClick(Sender: TObject);
var w,h:integer;
begin
w:=bm.Width;
h:=BM.Height;
Paintbox1.Width:=w*16;
Paintbox1.Height:=h*16;

case RGZoom.ItemIndex of
0: begin Zoom:=1; w:=bm.Width; h:=BM.Height; end;
1: begin Zoom:=4; w:=bm.Width*4; h:=BM.Height*4; end;
2: begin Zoom:=16; w:=bm.Width*16; h:=BM.Height*16; end;
end;

Paintbox1.Refresh;
PaintBox1.canvas.stretchDraw(Rect(0,0,w,h),bm);

end;

procedure TForm1.FormCreate(Sender: TObject);
begin
BM:=TBitmap.create;

end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
bm.free;

end;

procedure TForm1.PaintBox1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
if (ssLeft in shift) AND (RGTool.itemindex=0)then
   DrawPixes(x,y,panel1.color);
end;

procedure TForm1.PaintBox1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
XU:=X;YU:=Y;


  case RGTool.itemindex of
  0: if (XU = XD) and (YU=YD) then DrawPixes(x,y,panel1.color);
  1: DrawLine(xd,yd,xu,yu,zoom, Panel1.color);
  2: DrawCircle(xd,yd,xu,yu,zoom, Panel1.color);
  3: DrawBox(xd,yd,xu,yu,zoom, Panel1.color);
  4: Flood(xd,yd, Panel1.color);

  end;

end;

procedure TForm1.DrawLine(xS,YS,xE,yE,size:integer; Col:TColor);
begin
     paintbox1.Canvas.MoveTo(xS,yd);
     paintbox1.Canvas.pen.Color :=col;
     paintbox1.Canvas.pen.Width:=size;
     paintbox1.Canvas.LineTo(xE,yE);
end;

procedure TForm1.DrawCircle(xS,YS,xE,yE,size:integer; Col:TColor);
begin
     paintbox1.Canvas.MoveTo(xS,yd);
     paintbox1.Canvas.pen.Color :=col;
     paintbox1.Canvas.pen.Width:=size;
     paintbox1.Canvas.brush.Style :=bsClear;
     paintbox1.Canvas.Ellipse(xs,ys,xe,ye);
end;

procedure TForm1.DrawBox(xS,YS,xE,yE,size:integer; Col:TColor);
begin
     paintbox1.Canvas.MoveTo(xS,yd);
     paintbox1.Canvas.pen.Color :=col;
     paintbox1.Canvas.pen.Width:=size;
     paintbox1.Canvas.brush.Style :=bsClear;
     paintbox1.Canvas.Rectangle(xs,ys,xe,ye);

end;

procedure TForm1.Flood(xS,YS :integer; Col:TColor);
var c:TColor;
begin
     paintbox1.Canvas.brush.Color:=Col;
     c:=paintbox1.Canvas.Pixels[xs,ys];
     paintbox1.Canvas.FloodFill(xs,ys,c,fsSurface);
end;

end.
(*
===========================================
The form:
===========================================
*)
object Form1: TForm1
  Left = 233
  Top = 107
  Width = 696
  Height = 480
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Shell Dlg 2'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object PaintBox1: TPaintBox
    Left = 32
    Top = 24
    Width = 321
    Height = 329
    OnMouseDown = PaintBox1MouseDown
    OnMouseMove = PaintBox1MouseMove
    OnMouseUp = PaintBox1MouseUp
  end
  object Button1: TButton
    Left = 32
    Top = 368
    Width = 75
    Height = 25
    Caption = 'Load'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Panel1: TPanel
    Left = 32
    Top = 400
    Width = 73
    Height = 25
    Caption = 'Color'
    TabOrder = 1
    OnClick = Panel1Click
  end
  object rgZoom: TRadioGroup
    Left = 128
    Top = 360
    Width = 89
    Height = 65
    Caption = 'Zoom'
    ItemIndex = 0
    Items.Strings = (
      '1'
      '4'
      '16')
    TabOrder = 2
    OnClick = rgZoomClick
  end
  object RGTool: TRadioGroup
    Left = 248
    Top = 328
    Width = 89
    Height = 113
    Caption = 'RGTool'
    ItemIndex = 0
    Items.Strings = (
      'Free line'
      'Line'
      'Circle'
      'Rectangle'
      'Flodfill')
    TabOrder = 3
  end
  object CD: TColorDialog
    Ctl3D = True
    Left = 16
    Top = 400
  end
end