如何在视频窗口绘制截图框

Question

用videocap控件作照片采集，想在视频窗口出现一矩形截图框，可拖动，截取框内的图像，怎么实现？

Answer 1

以下代码用镂空窗口作一个框可以拖动unit SimpleF;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ExtCtrls,ShellAPI, AppEvnts;
const LWidth = 4;
      TrayIconID = 335;
type
  TfmSimple = class(TForm)
    ApplicationEvents1: TApplicationEvents;
    procedure FormResize(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure ApplicationEvents1Deactivate(Sender: TObject);
  private
    procedure WmNCHitTest(var Msg : TWMNCHitTest); message WM_NCHITTEST;
    procedure WindowMove(var Msg: TMsg);message WM_MOVE;
  end;var
  fmSimple: TfmSimple;
  bTemp: Boolean = False;
  Nid: TNotifyIconData;
implementationuses MainF;{$R *.DFM}procedure TfmSimple.WmNCHitTest(var Msg: TWMNCHitTest);
const v=4; //border width
var
  p:TPoint;
begin
  Inherited;
  if NOT fmMain.panOperation.Enabled then Exit;  p:=Point(Msg.XPos,Msg.YPos);
  p:=ScreenToClient(p);  if PtInRect(Rect(0,0,v,v),p) then
  Msg.Result:=HTTOPLEFT  else if PtInRect(Rect(Width-v,Height-v,Width,Height),p) then
  Msg.Result:=HTBOTTOMRIGHT  else if PtInRect(Rect(Width-v,0,Width,v),p) then
  Msg.Result:=HTTOPRIGHT  else if PtInRect(Rect(0,Height-v,v,Height),p) then
  Msg.Result:=HTBOTTOMLEFT  else if PtInRect(Rect(v,0,Width-v,v),p) then
  Msg.Result:=HTTOP  else if PtInRect(Rect(0,v,v,Height-v),p) then
  Msg.Result:=HTLEFT  else if PtInRect(Rect(Width-v,v,Width,Height-v),p) then
  Msg.Result:=HTRIGHT  else if PtInRect(Rect(v,Height-v,Width-v,Height),p) then
  Msg.Result:=HTBOTTOM;  if PtInRect(Rect(LWidth,0,Width - LWidth,LWidth),p) then
  Msg.Result := HTCAPTION;end;procedure TfmSimple.FormResize(Sender: TObject);
begin
  BeginPath(Canvas.handle);
  SetBkMode(Canvas.Handle,TRANSPARENT );
  canvas.Polygon([Point(0,0),Point(Width,0),
                    Point(Width,Height),Point(0,Height),
                    Point(0,0)]);
  Canvas.MoveTo(LWidth,LWidth);
  Canvas.LineTo(Width - LWidth,LWidth);
  Canvas.LineTo(Width -LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,LWidth);  EndPath(canvas.handle);  SetWindowRgn(Handle,PathToRegion(canvas.Handle), true );
end;procedure TfmSimple.FormCreate(Sender: TObject);
begin
  //限定窗口形关为一方框
  Canvas.Pen.Width := 1;
  BeginPath(canvas.handle);
    SetBkMode(Canvas.Handle,TRANSPARENT );
    canvas.Polygon([Point(0,0),Point(Width,0),
                    Point(Width,Height),Point(0,Height),
                    Point(0,0)]);
  Canvas.MoveTo(LWidth,LWidth);
  Canvas.LineTo(Width - LWidth,LWidth);
  Canvas.LineTo(Width -LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,LWidth);
  EndPath(canvas.handle);  SetWindowRgn(Handle,PathToRegion(canvas.Handle), true );
end;procedure TfmSimple.WindowMove(var Msg: TMsg);
begin
  inherited;
  BeginPath(Canvas.handle);
  SetBkMode(Canvas.Handle,TRANSPARENT );
  canvas.Polygon([Point(0,0),Point(Width,0),
                    Point(Width,Height),Point(0,Height),
                    Point(0,0)]);
  Canvas.MoveTo(LWidth,LWidth);
  Canvas.LineTo(Width - LWidth,LWidth);
  Canvas.LineTo(Width -LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,Height -LWidth);
  Canvas.LineTo(LWidth,LWidth);
  EndPath(canvas.handle);
  SetWindowRgn(Handle,PathToRegion(canvas.Handle), true );
end;
end.

Answer 2

怎么会不能移动呢应该是你的PTINRECT这里的数字出了点问题吧