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Inverting and decreasing colors in bitmap...

Posted on 2000-03-09
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Last Modified: 2010-04-04
I use the following to get a screen-capture. However, I want to decrease the colordepth, invert the colors and maybe decrease the resolution. Is this possible ?

Thanx !
/Erik N

procedure TForm3.BitBtn3Click(Sender: TObject);
var
    DC:HDC;
    Bmp:TBitmap ;
begin
    Application.minimize;
    sleep(Delay);
    DC:=getDC(GetDeskTopWindow);
    Bmp:=TBitmap.Create;
    Bmp.Width:=Screen.Width;
    Bmp.Height:=Screen.Height;
    BitBlt(Bmp.Canvas.Handle,0,0,Screen.Width,Screen.Height,DC,0,0,SRCCOPY);
    Image1.Picture.Bitmap:=Bmp;
    ReleaseDC(DC,DC);
    Bmp.Free;
    Application.restore;
end;
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Question by:Erik N
  • 5
7 Comments
 
LVL 13

Expert Comment

by:Epsylon
ID: 2600206
To reduce color try:

Image1.Picture.Bitmap.PixelFormat := pf8bit;


To resize set Image1.Stretch to true and change Image1.Width and Image1.Height
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LVL 13

Expert Comment

by:Epsylon
ID: 2600218
You can also use StretchBlt instead of BitBlt...
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Expert Comment

by:Epsylon
ID: 2600221
I never tried it but maybe InvertRect can be used to invert the colors.
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Expert Comment

by:AttarSoftware
ID: 2600273
BitBlt( Bmp.Canvas.Handle, 0, 0, Screen.Width, Screen.Height, 0, 0, 0, DSTINVERT ) ;

Will invert the colors...

As Epsylon said, StretchBlt will reduce the resoloution, and as for reducing colors, you might have to create another bitmap, set its pixelformat to whatever (as Epsylon said again), and then BitBlt the bitmap across...

If that doesn't work, then you are into some hefty color reduction algorythms (boo) ;O)

Good Luck,

Tim.
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LVL 13

Accepted Solution

by:
Epsylon earned 200 total points
ID: 2601875
This works:


procedure TForm1.Button1Click(Sender: TObject);
var w,h:Integer;
    DC:HDC;
    Bmp:TBitmap ;
begin
    w:=500;
    h:=500;
    Visible := false;
    sleep(250);
    DC:=getDC(GetDeskTopWindow);
    Bmp:=TBitmap.Create;
    Bmp.Width:=w;
    Bmp.Height:=h;
    BitBlt    (Bmp.Canvas.Handle,0,0,Screen.Width,Screen.Height,DC,0,0,SRCCOPY);
    StretchBlt(Bmp.Canvas.Handle,0,0,w,h,DC,0,0,Screen.Width,Screen.Height,SRCCOPY);
    InvertRect(Bmp.Canvas.Handle,Rect(0,0,w,h));
    Bmp.PixelFormat := pf8bit;
    Image1.Picture.Bitmap:=Bmp;
    ReleaseDC(DC,DC);
    Bmp.Free;
    Visible := true;
end;


Cheers,

Epsylon.
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LVL 13

Expert Comment

by:Epsylon
ID: 2601882
Oops, I forgot to strip-out the line

BitBlt(Bmp.Canvas.Handle,0,0,Screen.Width,Screen.Height,DC,0,0,SRCCOPY);


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Author Comment

by:Erik N
ID: 2605124
Nice !
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