再学 GDI+[12]: 准备工作 - 矩形命中

本例效果图:

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    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);
    procedure FormPaint(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
  f: Boolean;
  x1,y1,x2,y2: Integer;
  RectArr: array of TRect;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  f := True;
  x1 := X;
  y1 := Y;
  x2 := X;
  y2 := Y;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
var
  i: Integer;
begin
  if f then
  begin
    Canvas.DrawFocusRect(Rect(x1,y1,x2,y2));
    x2 := X;
    y2 := Y;
    Canvas.DrawFocusRect(Rect(x1,y1,x2,y2));
  end else begin
    Text := '';
    for i := Low(RectArr) to High(RectArr) do
      if PtInRect(RectArr[i], Point(X,Y)) then
        Text := Format('在第 %d 个矩形中', [i+1]);
  end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if not f then Exit;
  SetLength(RectArr, Length(RectArr)+1);
  RectArr[High(RectArr)] := Rect(x1,y1,x2,y2);
  f := False;
  Repaint;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
  i: Integer;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclRed, 1);
  g.Clear(aclWhite);

  for i := Low(RectArr) to High(RectArr) do
    g.DrawRectangle(p, MakeRect(RectArr[i]));

  g.Free;
  p.Free;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 179
  ClientWidth = 277
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnMouseDown = FormMouseDown
  OnMouseMove = FormMouseMove
  OnMouseUp = FormMouseUp
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
end