本例效果图:
代码文件:unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure FormPaint(Sender: TObject);
procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
private
procedure RectToPoints;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
img: TGPImage;
flag: Integer = -1;
ClickImg: Boolean;
rt: TRect;
pts: array[0..7] of TPoint;
x1,y1: Integer;
{从矩形中获取八个点, 因要反复使用, 故提取为一个独立的过程}
procedure TForm1.RectToPoints;
begin
pts[0] := rt.TopLeft;
pts[1] := Point(rt.Left, rt.Top + (rt.Bottom - rt.Top) div 2);
pts[2] := Point(rt.Left, rt.Bottom);
pts[3] := Point(rt.Left + (rt.Right - rt.Left) div 2, rt.Bottom);;
pts[4] := rt.BottomRight;
pts[5] := Point(rt.Right, rt.Top + (rt.Bottom - rt.Top) div 2);;
pts[6] := Point(rt.Right, rt.Top);;
pts[7] := Point(rt.Left + (rt.Right - rt.Left) div 2, rt.Top);
end;
procedure TForm1.FormCreate(Sender: TObject);
const
ImgPath = 'c:\temp\test.png';
var
w,h: Integer;
begin
if not FileExists(ImgPath) then Exit;
img := TGPImage.Create(ImgPath);
w := img.GetWidth;
h := img.GetHeight;
rt.Left := (ClientWidth - w) div 2;
rt.Top := (ClientHeight - h) div 2;
rt.Right := rt.Left + w;
rt.Bottom := rt.Top + h;
RectToPoints;
DoubleBuffered := True;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
img.Free;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
g: TGPGraphics;
p: TGPPen;
i: Integer;
begin
g := TGPGraphics.Create(Canvas.Handle);
p := TGPPen.Create(aclRed);
g.DrawImage(img, MakeRect(rt));
if ClickImg then
for i := 0 to Length(pts) - 1 do
g.DrawRectangle(p, MakeRect(pts[i].X - 3, pts[i].Y - 3, 6, 6));
p.Free;
g.Free;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
var
i: Integer;
begin
flag := -1;
for i := 0 to Length(pts) - 1 do
if PtInRect(Bounds(pts[i].X - 3, pts[i].Y - 3, 6, 6), Point(X, Y)) then
begin
flag := i;
Break;
end;
if flag = -1 then
begin
ClickImg := PtInRect(rt, Point(X,Y));
Repaint;
end else begin
x1 := X;
y1 := Y;
end;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if flag = -1 then Exit;
case flag of
0: begin Inc(rt.Left, X-x1); Inc(rt.Top, Y-y1) end;
1: begin Inc(rt.Left, X-x1) end;
2: begin Inc(rt.Left, X-x1); Inc(rt.Bottom, Y-y1) end;
3: begin Inc(rt.Bottom, Y-y1) end;
4: begin Inc(rt.Right, X-x1); Inc(rt.Bottom, Y-y1) end;
5: begin Inc(rt.Right, X-x1) end;
6: begin Inc(rt.Right, X-x1); Inc(rt.Top, Y-y1) end;
7: begin Inc(rt.Top, Y-y1) end;
end;
x1 := X;
y1 := Y;
RectToPoints;
Repaint;
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
flag := -1;
end;
end.
窗体文件:object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 246
ClientWidth = 346
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
Position = poDesktopCenter
OnCreate = FormCreate
OnDestroy = FormDestroy
OnMouseDown = FormMouseDown
OnMouseMove = FormMouseMove
OnMouseUp = FormMouseUp
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
end