ma xiaoguang

Dear ladies and gentlemen,

I want to make such tool for my application which called Magnetic Lasso
Tool in Photoshop or Intelligent Scissors Tool in GIMP, although they are
not absolutely same in the both applications.

I have been checked out the source code of the Intelligent Scissors of
GIMP 2.2.10 . But the amount of routines related to this technique is so
huge, and the pointer operations in C is so complex, until now, I couldn't
understand the code in GIMP which related to this tool, and translate it to
Pascal.

I have tried to make it by myself. But in vain. My code is in the
following (could only manipulate the absolute vertical line):

///////////////////////////

unit Main;

interface

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

type
TfrmMain = class(TForm)
Panel1: TPanel;
StatusBar: TStatusBar;
ScrollBox1: TScrollBox;
imgDrawingArea: TImage;
OpenPictureDialog: TOpenPictureDialog;
btnOpenImage: TButton;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure btnOpenImageClick(Sender: TObject);
procedure imgDrawingAreaMouseDown(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
procedure imgDrawingAreaMouseMove(Sender: TObject; Shift: TShiftState;
X, Y: Integer);
procedure imgDrawingAreaMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
private
{ Private declarations }
FOriginalBitmap: TBitmap;
FDrawing : Boolean;
FStart, FEnd : TPoint;
FPoints : array of TPoint;

procedure CalculatePoints(const SampleBitmap: TBitmap;
const PointA, PointB: TPoint; const Radius, Fuzziness: Integer);
public
{ Public declarations }
end;

var
frmMain: TfrmMain;

implementation

uses
Math;

{$R *.dfm}

procedure TfrmMain.CalculatePoints(const SampleBitmap: TBitmap;
const PointA, PointB: TPoint; const Radius, Fuzziness: Integer);
var
BaseColor, CurColor, NearColor: TColor;
sx, sy, ex, ey, ix, iy : Integer;
Slope : Extended;
i, j, x, y, Length : Integer;
begin
BaseColor := SampleBitmap.Canvas.Pixels[PointA.X, PointA.Y];

sx := MinIntValue([PointA.X, PointB.X]);
sy := MinIntValue([PointA.Y, PointB.Y]);
ex := MaxIntValue([PointA.X, PointB.X]);
ey := MaxIntValue([PointA.Y, PointB.Y]);

SetLength(FPoints, 0);
SetLength( FPoints, High(FPoints) + 2 );
FPoints[High(FPoints)] := Point(sx, sy);

if (ex - sx) = 0 then
begin
for i := 1 to (ey - sy - 1) do
begin
ix := sx;
NearColor := SampleBitmap.Canvas.Pixels[sx, sy + i];
for j := (sx - Radius) to (sx + Radius) do
begin
if j = sx
then Continue;

CurColor := SampleBitmap.Canvas.Pixels[j, sy + i];
if Abs(CurColor - BaseColor) < Abs(NearColor - BaseColor) then
begin
NearColor := CurColor;
ix := j;
end;
end;

SetLength( FPoints, High(FPoints) + 2 );
FPoints[High(FPoints)] := Point(ix, sy + i);
end;
end;

SetLength( FPoints, High(FPoints) + 2 );
FPoints[High(FPoints)] := Point(ex, ey);
end; { CalculatePoints }

procedure TfrmMain.FormCreate(Sender: TObject);
begin
FOriginalBitmap := nil;
FStart := Point(0, 0);
FEnd := Point(0, 0);
FDrawing := False;
FPoints := nil;
end; { FormCreate }

procedure TfrmMain.FormDestroy(Sender: TObject);
begin
FOriginalBitmap.Free;
end; { FormDestroy }

procedure TfrmMain.btnOpenImageClick(Sender: TObject);
var
Picture: TPicture;
begin
if OpenPictureDialog.Execute then
begin
if Assigned(FOriginalBitmap) then
begin
FOriginalBitmap.Free;
FOriginalBitmap := nil;
end;

FOriginalBitmap := TBitmap.Create;

Picture := TPicture.Create;
try
Picture.LoadFromFile(OpenPictureDialog.FileName);

try
FOriginalBitmap.Assign(Picture.Graphic);
FOriginalBitmap.PixelFormat := pf24bit;
except
FOriginalBitmap.Width := Picture.Graphic.Width;
FOriginalBitmap.Height := Picture.Graphic.Height;
FOriginalBitmap.PixelFormat := pf24bit;
FOriginalBitmap.Canvas.Draw(0, 0, Picture.Graphic);
end;

imgDrawingArea.Picture.Graphic := FOriginalBitmap;
finally
Picture.Free;
end;
end;
end; { btnOpenImageClick }

procedure TfrmMain.imgDrawingAreaMouseDown(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
imgDrawingArea.Picture.Graphic := FOriginalBitmap;
FStart := Point(X, Y);
FEnd := Point(X, Y);
imgDrawingArea.Canvas.Pen.Mode := pmNotXor;
FDrawing := True;
end; { imgDrawingAreaMouseDown }

procedure TfrmMain.imgDrawingAreaMouseMove(Sender: TObject;
Shift: TShiftState; X, Y: Integer);
begin
if FDrawing then
begin
with imgDrawingArea.Canvas do
begin
MoveTo(FStart.X, FStart.Y);
LineTo(FEnd.X, FEnd.Y);
FEnd := Point(X, Y);
MoveTo(FStart.X, FStart.Y);
LineTo(FEnd.X, FEnd.Y);
end;
end;

StatusBar.Panels[0].Text := Format('X: %d, Y: %d', [X, Y]);
end; { imgDrawingAreaMouseMove }

procedure TfrmMain.imgDrawingAreaMouseUp(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
FDrawing := False;
imgDrawingArea.Picture.Graphic := FOriginalBitmap;
imgDrawingArea.Canvas.Pen.Mode := pmNotXor;
FEnd := Point(X, Y);
CalculatePoints(FOriginalBitmap, FStart, FEnd, 10, 0);
imgDrawingArea.Canvas.Polyline(FPoints);
imgDrawingArea.Canvas.Pen.Mode := pmCopy;
end; { imgDrawingAreaMouseUp }

end.

///////////////////


Could you please give me some suggestions on how to achieve this tool?
Help me, please. Thank you very much.

Best regards.

Xiaoguang

jens gruschel

to enhance it, after all you just have to calculate the result over and
over again when the mouse is moved (if I understand it the right way). I
don't know where to find the source code, but maybe you can google the
web or the groups. Good luck!

--
Jens Gruschel
http://www.pegtop.net

ma xiaoguang

Hi Jens,

Thanks for your help. I found the paper which was about Intelligent
Scissors at

<http://web.engr.oregonstate.edu/~enm/publications/SIGGRAPH_95/scissors_comp.pdf>

Because of my poor English, I can hardly understand the principle about
the paper clearly. I will continually study the paper. If I know how to
achieve the Intelligent Scissors Tool, I will distribute the code.

Yes, he is a master. I found the Magic Wand algorithm from his website.
I wish that I could get the Lasso code, too.

Thank you very much.

Xiaoguang

jens gruschel

I wasn't aware of the difference. I thought a magnetic lasso is a magic
wand or at least based on it. But it seems that the lasso is based on
gradients while the wand makes use of gray value thresholds. Sorry about
that.

--
Jens Gruschel
http://www.pegtop.net

ma xiaoguang

Hi Jens,


Yes, they are different. Don't worry about it. I think that I will
definitely achieve it. Thanks for your reply.

Best regards.

Xiaoguang