图像格式转换问题(在内存中)

Question

RectWidth:=RightPos-LeftPos;
RectHeight:=BottomPos-TopPos;
SourceDC:=CreateDC('DISPLAY',nil,nil,nil);
DestDC:=CreateCompatibleDC(SourceDC);
Bhandle:=CreateCompatibleBitmap(SourceDC,RectWidth,RectHeight);
SelectObject(DestDC,Bhandle);
BitBlt(DestDC,0,0,RectWidth,RectHeight,SourceDC,LeftPos,TopPos,SRCCOPY);
Bitmap:=TBitmap.Create;
Bitmap.Handle:=BHandle; Bitmap.SaveToFile ('C:\Log');
         Bitmap.LoadFromFile('C:\Log');  //为什么不用这两句会出错?  Jpeg:=TJpegImage.Create ;
Jpeg.Assign (Bitmap);
Jpeg.JPEGNeeded ;
jpeg.CompressionQuality :=Quality;
jpeg.Compress ;
    Jpeg.SaveToStream (BmpStream);
//BitMap.SaveToStream(BmpStream);
BmpStream.Position:=0;
LeftSize:=BmpStream.Size;
Jpeg.Free;
Bitmap.free;
DeleteDC(DestDC);
ReleaseDC(Bhandle,SourceDC);怎样利用api截取屏幕后,在内存中转换为jpg图像格式,使用Stream?

Answer 1

Bitmap.Handle:=BHandle;引起的，好像是，建议直接画到Bitmap.

Answer 2

给你段代码
procedure TForm1.ServerSocket1ClientRead(Sender: TObject;
  Socket: TCustomWinSocket);
var
  s,s1:string;
  desk:tcanvas;
  bitmap:tbitmap;
  jpg:tjpegimage;
begin
  s:=socket.ReceiveText;
  if s='gets' then //file://客户端发出申请
  begin
   try
    m1:=tmemorystream.Create;
    bitmap:=tbitmap.Create;
    jpg:=tjpegimage.Create;
    desk:=tcanvas.Create; //以下代码为取得当前屏幕图象
    desk.Handle:=getdc(hwnd_desktop);
    with bitmap do
    begin
        width:=screen.Width;
        height:=screen.Height;
        canvas.CopyRect(canvas.cliprect,desk,desk.cliprect);
    end;
    jpg.Assign(bitmap); //file://将图象转成JPG格式
    jpg.CompressionQuality:=10;//文件压缩大小设置
    //m1.clear;
    jpg.SaveToStream(m1); //file://将JPG图象写入流中
    jpg.free;
    m1.Position:=0;
    s1:=inttostr(m1.size);
    Socket.sendtext(s1); //file://发送图象大小
   finally
    bitmap.free;
    desk.free;
   end;
  end;
  if s='okok' then //file://客户端已准备好接收图象
  begin
    m1.Position:=0;
    Socket.SendStream(m1); //file://发送JPG图象
  end;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
 ServerSocket1.open;
end;procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
ServerSocket1.close;
end;end.

Answer 3

var
  bitmap:TBitmap;
  Stream:TStringStream;
  Jpeg:TJPEGImage;
  dc:HDC;
begin
  bitmap := TBitmap.Create;
  Jpeg:=TJPEGImage.Create;
  Stream:=TStringStream.Create('F:\3.txt');
  try
    bitmap.Width:=200;
    bitmap.Height:=200;
    dc:=GetDC(0);//屏幕
    BitBlt(bitmap.Canvas.Handle,0,0,200,200,dc,0,0,SRCCOPY);
    Jpeg.Assign(bitmap);
    jpeg.CompressionQuality :=75;
  jpeg.Compress ;
    Jpeg.SaveToStream(stream);    //Jpeg.SaveToFile('F:\1.jpg');
  finally
    Jpeg.Free;
    Stream.Free;
    bitmap.Free;
  end;