Add dropshadow to a TBitmap - delphi

Question

I have a routine that takes screenshots (TBitmap), I need to add drop-shadow to the final TBitmap/image, I have this code (which used to work but...) something isn't right, the drop-shadow simply isn't drawn:
// --------------------------------------------------------------------- //
procedure TakeScreenshot();
var
lCapRect : TRect;
DestBitmap : TBitmap;
begin
// Take the screenshot & assign it to DestBitmap
// ...
// Add the drop shadow to DestBitmap
DestBitmap.Width := DestBitmap.Width + 6;
DestBitmap.Height := DestBitmap.Height + 6;
PaintShadow(DestBitmap.Canvas, lCapRect);
end;
// --------------------------------------------------------------------- //
procedure PaintShadow(ACanvas : TCanvas; ARect : TRect);
var
AColor : TColor;
i, iMax : Integer;
h1, h2, v1, v2 : Integer;
begin
AColor := ACanvas.Brush.Color;
iMax := 6;
h1 := ARect.Left;
h2 := ARect.Right;
v1 := ARect.Top;
v2 := ARect.Bottom;
with ACanvas do
begin
for i := iMax downto 0 do
begin
ACanvas.Pen.Mode := pmMask;
Pen.Color := DarkenColorBy(AColor, ((iMax - i) * 4 + 10));
MoveTo(h1 + 4{i}, v2 + i);
LineTo(h2 + i + 1, v2 + i);
end; // for
for i := iMax downto 0 do
begin
ACanvas.Pen.Mode := pmMask;
Pen.Color := DarkenColorBy(AColor, ((iMax - i) * 4 + 10));
MoveTo(h2 + i, v1 + 4{i});
LineTo(h2 + i, v2 + i);
end; // for
end; // with
end;
// --------------------------------------------------------------------- //
function Max(const A, B: Integer): Integer;
begin
if (A > B) then
Result := A
else
Result := B;
end;
// --------------------------------------------------------------------- //
function DarkenColorBy(BaseColor : TColor; Amount : Integer) : TColor;
begin
Result := RGB(Max(GetRValue(ColorToRGB(BaseColor)) - Amount, 0),
Max(GetGValue(ColorToRGB(BaseColor)) - Amount, 0),
Max(GetBValue(ColorToRGB(BaseColor)) - Amount, 0));
end;
My question is: How can I fix this (OR anyone know a simple way to add dropshadow to a TBitmap)?
The final image is meant to be saved as bmp/jpg, not shown in a TImage, so I really need to add drop shadow to the image itself.
PS. I'm using Delphi 7 Pro, my app is restricted to Windows XP or later
EDIT
lCapRect depends on the settings (whether I'm capturing the active monitor, window or all the desktop monitors), but let's say it's calculated this way:
lCapRect.Right := Screen.DesktopLeft + Screen.DesktopWidth;
lCapRect.Bottom := Screen.DesktopTop + Screen.DesktopHeight;
lCapRect.Left := Screen.DesktopLeft;
lCapRect.Top := Screen.DesktopTop;
The bitmap does contain the screenshot (+ 6 pixels added to the bottom & right sides to make room for the dropshadow), it's just that the drop shadow drawing doesn't happen

Answer 1

You haven't shown how you are calculating lCapRect. For not drawing off the bitmap regarding your PaintShadow procedure, it has to be smaller than the bitmap, example:
lCapRect := DestBitmap.Canvas.ClipRect;
// Add the drop shadow to DestBitmap
DestBitmap.Width := DestBitmap.Width + 6;
DestBitmap.Height := DestBitmap.Height + 6;
PaintShadow(DestBitmap.Canvas, lCapRect);