How to make text glow - delphi

Question

Having my self-written button control (TMyButton) derived from TCustomControl I want to add an ability to make glow effect for MyButton's caption. After long time in Goolge I understood that the best way to create glow is to draw text with specify color, then blurring all - text and surface on which it is lies, and then draw text again. It will works perfectly only if surface is solid, e.g. fills with red color.
I have created procedure that make Bitmap blurred, but my button can have non-solid background, e.g bitmap which can be filled gradient. If I will blur that background it became very awful, but glow looks nice.
I suggest that this task could be solved by using Scanline, but I have no idea what exactly I should do with it.
If use solid fill I have this (filled with clWhite):
If use bitmap fill I have this ("Text" has clBlack shadow):
That is how looks blurred bitmap shown above, without blur:
Does anybody has any idea how to make glow effect for text without blurring a result bitmap?
P.S.
code to blur bitmap
procedure DrawBlurEffect(BmpInOut: TBitmap; Radius: Integer);
var
A, B, C, D: PRGBArray;
x, y, i: Integer;
begin
BmpInOut.PixelFormat := pf24bit;
for i:=0 to Radius do
begin
for y:=2 to BmpInOut.Height - 2 do
begin
A := BmpInOut.ScanLine[y-1];
B := BmpInOut.ScanLine[y];
C := BmpInOut.ScanLine[y+1];
D := BmpInOut.ScanLine[y];
for x:=1 to BmpInOut.Width - 2 do
begin
B[x].Red := Trunc(C[x].Red + A[x].Red + B[x-1].Red + D[x+1].Red) div 4;
B[x].Green := Trunc(C[x].Green + A[x].Green + B[x-1].Green + D[x+1].Green) div 4;
B[x].Blue := Trunc(C[x].Blue + A[x].Blue + B[x-1].Blue + D[x+1].Blue) div 4;
end;
end;
end;
end;

Answer 1

Draw text on the glass (vista and above) using DrawThemeTextEx with set DTTOPT glow flag.
uses Types, UxTheme, Themes, Graphics;
procedure DrawGlassText(Canvas: TCanvas; GlowSize: Integer; var Rect: TRect;
var Text: UnicodeString; Format: DWORD); overload;
var
DTTOpts: TDTTOpts;
begin
if Win32MajorVersion < 6 then
begin
DrawTextW(Canvas.Handle, PWideChar(Text), Length(Text), Rect, Format);
Exit;
end;
ZeroMemory(#DTTOpts, SizeOf(DTTOpts));
DTTOpts.dwSize := SizeOf(DTTOpts);
DTTOpts.dwFlags := DTT_COMPOSITED or DTT_TEXTCOLOR;
if Format and DT_CALCRECT = DT_CALCRECT then
DTTOpts.dwFlags := DTTOpts.dwFlags or DTT_CALCRECT;
DTTOpts.crText := ColorToRGB(Canvas.Font.Color);
if GlowSize > 0 then
begin
DTTOpts.dwFlags := DTTOpts.dwFlags or DTT_GLOWSIZE;
DTTOpts.iGlowSize := GlowSize;
end;
with ThemeServices.GetElementDetails(teEditTextNormal) do
DrawThemeTextEx(ThemeServices.Theme[teEdit], Canvas.Handle, Part, State,
PWideChar(Text), Length(Text), Format, #Rect, DTTOpts);
end;
There is TransparentCanvas that can be used to set glow color.
As a funfact :). I remember, that some components (d2) to mimic glow-effect, used simple (poor) technique - text behind with specific glow color - shadow.
procedure TExampleGlowLabel.DoDrawText( var Rect : TRect; Flags : Word );
var
Text : array[ 0..255 ] of Char;
TmpRect : TRect;
begin
GetTextBuf(Text, SizeOf(Text));
if ( Flags and DT_CALCRECT <> 0) and
( ( Text[0] = #0 ) or ShowAccelChar and
( Text[0] = '&' ) and
( Text[1] = #0 ) ) then
StrCopy(Text, ' ');
if not ShowAccelChar then
Flags := Flags or DT_NOPREFIX;
Canvas.Font := Font;
if FGlowing and Enabled then
begin
TmpRect := Rect;
OffsetRect( TmpRect, 1, 1 );
Canvas.Font.Color := GlowColor;
DrawText(Canvas.Handle, Text, StrLen(Text), TmpRect, Flags);
TmpRect := Rect;
OffsetRect( TmpRect, -1, -1 );
Canvas.Font.Color := GlowColor;
DrawText(Canvas.Handle, Text, StrLen(Text), TmpRect, Flags);
TmpRect := Rect;
OffsetRect( TmpRect, -1, 1 );
Canvas.Font.Color := GlowColor;
DrawText(Canvas.Handle, Text, StrLen(Text), TmpRect, Flags);
TmpRect := Rect;
OffsetRect( TmpRect, 1, -1 );
Canvas.Font.Color := GlowColor;
DrawText(Canvas.Handle, Text, StrLen(Text), TmpRect, Flags);
end;
Canvas.Font.Color := Font.Color;
if not Enabled then
Canvas.Font.Color := clGrayText;
DrawText(Canvas.Handle, Text, StrLen(Text), Rect, Flags);
end;
As mentioned in comment TButton with transparent PNG image and glowing hover effect has answer with some non-free components.
edit
Different approach would be to use FireMonkey Effects (really cool) TGlowEffect, but probably, it applies to whole canvas.