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Romain Chagot · Guest

I get a HBitmap and i assign it to a TBitmap.handle property...
after i want to assign the tbitmap to a TJpegImage component but it doesn't
work... i get a white picture :/

image: TPaintBox;
hdcCompatible: HBITMAP;

procedure TForm1.FormCreate(Sender: TObject);
begin
bmp := TBitmap.Create;
jpg := TJpegImage.Create;
stream := TMemoryStream.Create;

hdcScreen := CreateDC('DISPLAY', nil, nil, nil);

screen_width := GetDeviceCaps(hdcScreen, HORZRES);
screen_height := GetDeviceCaps(hdcScreen, VERTRES);

bmp.width := 640; //static values only for test and to speed up
computing
bmp.height := 480;
//bmp.width := screen_width;
//bmp.height := screen_height;

//------- initializations for screenshoting -------------
hdcCompatible := CreateCompatibleDC(hdcScreen);

hbmScreen := CreateCompatibleBitmap(hdcScreen, screen_width,
screen_height);

if hbmScreen = 0 then
messagedlg('hbmScreen', mtError, [mbOK], 0);

hSelectObject := SelectObject(hdcCompatible, hbmScreen);

if (hSelectObject = NULLREGION) or (hSelectObject = GDI_ERROR) then
messagedlg('Compatible Bitmap Selection', mtError, [mbOK], 0);
//------- end of initializations -------------

bmp.Canvas.Handle := hdcCompatible; //"bmp.handle := hdcCompatible;"
seems not to work at all

end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
BitBlt(hdcCompatible,
0, 0, bmp.width, bmp.height,
hdcScreen,
0, 0,
SRCCOPY); //taking a screenshot

//image.canvas.Draw(0,0,bmp); //that works

jpg.pixelformat := jf24bit;
jpg.assign(bmp);
jpg.Compress;
image.Canvas.Draw(0,0,jpg); //i get a white picture
jpg.SaveToStream(stream);
client.SendBuffer(stream, stream.size);
stream.clear;
end;

I tried to assign it to another TBitmap instead of a TJpegImage but i failed
too...
the only working way I found is :
bmp2.canvas.draw(0, 0, bmp);
but it's not clean and it slow down computing... I would like to do a 25 fps
treatment (maybe i'm dreaming)

if someone could help me.......

thanx

Maynard Philbrook · Guest

Try to initiate a Canvas in the Timer event to copy the screen data to the
bitmap.
or simply create a global Canvas to save time like this.
// global section
var
screenShotDC:Tcanvas; // create at run time.
ScreenBitmap:TBitmap;// create at run time..
ScreenJpeg:TJpegImage;
---
your timer event
---
Begin
ScreenShotDC.Handle := GetDC(GetDeskTopWindow);
ScreenBitMap.Canvas.CopyRect(ScreenShotDC.ClipRect,ScreenShotDC,
ScreenShotDC.ClipRect);
ReleaseDC(GetDeskTopWindow, ScreenShotDC.Handle);
ScreenJpeg.Assign(ScreenBitMap);
ScreenJpeg.SaveToStream(.....);/

Romain Chagot wrote:

Joris · Guest

"Romain Chagot" <romain.chagot (AT) free (DOT) fr> wrote