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問題は次のとおりです。マウスの移動中にデスクトップに長方形を描画します（長方形のサイズが大きくなります）ラグやアーティファクトなどはありません。すべて問題ありません： ここに画像の説明を入力

しかし、四角形のサイズをビードよりも小さくすると、次のアーティファクトが発生します。 ここに画像の説明を入力

赤い四角形は実際の四角形で、その他はすべてバグです。

完璧な解決策はキャンバスを再描画することですが、マウスが動いている間は常にそれを行うことはできません.

移動後にマウスが絶対停止したときに解決策はありますか?

アップデート

コード：

    unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    Timer1: TTimer;
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
    procedure FormCreate(Sender: TObject);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    isDown: Boolean;
    downX, downY: Integer;
  public
    { Public declarations }
    Bild: TBitMap;
  end;

implementation

{ Form props: BorderStyle= bsNone AlphaBlend true, 150 Transparentcolor = true, clBlack }

{$R *.dfm}

procedure TForm2.FormCreate(Sender: TObject);
begin
  Bild := TBitMap.Create;
end;

procedure TForm2.FormDestroy(Sender: TObject);
begin
  Bild.Free;
end;

procedure TForm2.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  isDown := true;
  downX := X;
  downY := Y;
end;

procedure TForm2.FormMouseMove(Sender: TObject; Shift: TShiftState;
  X, Y: Integer);
const
  cVal = 4;
begin
  if isDown then
  begin
    Self.Canvas.Lock;
    Self.Repaint;
    Self.Canvas.Pen.Color := clNone;
    Self.Canvas.Pen.Width := 1;

    Self.Canvas.Pen.Style := psDot;
    //Self.Canvas.Pen.Mode := pmNotCopy;
    Self.Canvas.Brush.Color := clGreen;
    Self.Canvas.Rectangle(downX, downY, X, Y);
    Self.Canvas.Pen.Style := psSolid;
    Self.Canvas.Brush.Color := clNone;
    Self.Canvas.Unlock;
    { Self.Canvas.Rectangle(downX - cVal, downY - cVal, downX + cVal, downY + cVal);
     Self.Canvas.Rectangle(X - cVal, Y - cVal, X + cVal, Y + cVal);
     Self.Canvas.Rectangle(X - cVal, downY - cVal, X + cVal, downY + cVal);
     Self.Canvas.Rectangle(downX - cVal, Y - cVal, downX + cVal, Y + cVal);

     Self.Canvas.Rectangle(downX - cVal, (downY + Y) div 2 - cVal, downX + cVal,
       (downY + Y) div 2 + cVal);
     Self.Canvas.Rectangle(X - cVal, (downY + Y) div 2 - cVal, X + cVal,
       (downY + Y) div 2 + cVal);

     Self.Canvas.Rectangle((downX + X) div 2 - cVal, downY - cVal,
       (downX + X) div 2 + cVal, downY + cVal);
     Self.Canvas.Rectangle((downX + X) div 2 - cVal, Y - cVal, (downX + X) div 2 + cVal,
       Y + cVal);   }
  end;
end;

function CaptureRect(aRect: TRect; out aBmp: TBitmap): Boolean;
var
  ScreenDC: HDC;
begin
  Result := False;
  try
    with aBmp, aRect do
    begin
      Width := Right - Left;
      Height := Bottom - Top;
      ScreenDC := GetDC(0);
      try
        BitBlt(Canvas.Handle, 0, 0, Width, Height, ScreenDC, Left, Top, SRCCOPY);
      finally
        ReleaseDC(0, ScreenDC);
      end;
    end;
  except
  end;
end;

procedure TForm2.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  r: TRect;
begin
  isDown := false;
  r.Left := downX;
  r.Top := downY;
  r.Right := X;
  r.Bottom := Y;
  CaptureRect(r, Bild);
  Self.Close;
end;

end.
4

2 に答える 2

1

Paint into a layered window instead. That will give you great speed without the artefacts, and Windows takes care of the drawing.

A layered window is a window that is created by specifying WS_EX_LAYERED when creating the window with the CreateWindowEx function. Later you can use UpdateLayeredWindow in order to set the content of this window. That way you can paint on top of a canvas without modifying the content of the canvas.

Of course this is a more advanced approach to solving your problem. So you need to have some knowledge about the Windows API.

于 2014-07-24T11:24:56.950 に答える