Question

Windows XP使用漂亮的阴影绘制图标文本，这有助于阅读各种背景上的文本。字体颜色为白色，阴影为黑色（如果桌面背景为白色）或者根本没有阴影（如果桌面背景为黑色）。

所以有两个子任务：

如何绘制阴影？它不是文本的简单x，y偏移量;阴影看起来更像是模糊。
如何使阴影在白色背景上变得更加明显，在黑暗中变得不那么明显？

我需要一个GDI解决方案（而不是GDI +）。

Answer 1

请阅读Glow and Shadow Effects using Windows GDI。

Answer 2

受Chris Becke's answer in this thread启发

如果您需要快速且不那么脏的解决方案，您可能还需要执行以下操作：

在黑色位图上绘制文本，然后将其与主要hdc进行alpha混合，但是：将目标矩形-1 ... 2移动x，使用-1 .. 3移动y（即循环中的多个混合）。要实现阴影褪色效果，请相应修改外部混合的SourceConstantAlpha（| x |＆gt; 1或| y |＆gt; 1）。

这是一个粗略的方法，随时可以尝试细节。

我不确定此类解决方案的性能和视觉质量方面，但在某些情况下可能就足够了。

Answer 3

另请参阅此处的DrawShadowText函数：Writing Transparent Text on Image

函数原型是这样的：procedure DrawShadowText（aCanvas：TCanvas; CONST Text：string; CONST X，Y，Opacity：Integer; TextColor，ShadowColor：TColor）;
它已准备好使用。

Answer 4

另一个DrawShadowText函数，这次基于MS Win API。需要Windows Vista及更高版本。

来源：https://www.delphipraxis.net/66678-drawshadowtext-delphi-commctrl-h-comctl32-dll-3.html

这是英文版本：

{-------------------------------------------------------------------------------------------------------------
  Unit ShadowText by Matthias G. aka turboPASCAL
  Version 1.0 (VCL)
  Draws text with shadow (This unit provides the function DrawShadowText from the ComCtl32.dll)

  Minimum req:
     Windows Vista
     Comctl32.dll v6

     If running under XP or without Windows XP Manifest, a substitute function is used to display the shadow.
     From the user manual: To use DrawShadowText, specify Comctl32.dll version 6 in the manifest. For more information on manifests, see Enabling Visual Styles.

  Src: https://www.delphipraxis.net/66678-drawshadowtext-delphi-commctrl-h-comctl32-dll-3.html
  API docs: https://docs.microsoft.com/en-us/windows/win32/api/commctrl/nf-commctrl-drawshadowtext
  Tester: c:\Myprojects\Project Testers\gr cGraphUtil.pas\
-------------------------------------------------------------------------------------------------------------}

UNIT ShadowText;

INTERFACE

USES
  Windows, SysUtils, System.Classes, Graphics;

VAR
   // determines whether the alternative shadow should be used if the function from ComCtl32.dll is not available
   UseLQShadow : Boolean = True;

  // Output of a text with shadow by specifying X and Y coordinates
  function DrawShadowText(ACanvas: TCanvas; x, y: Integer; AText: string; TextColor, ShadowColor: TColor; ShadowSpaceX, ShadowSpaceY: Integer): Integer;

  // Output of a text with shadow over a TRect structure with specification of the text formatting (text flags see Delphi help "DrawText")
  function DrawShadowTextR(ACanvas: TCanvas; TextRect: TRect; x, y: Integer; AText: string; TextColor, ShadowColor: TColor; ShadowSpaceX, ShadowSpaceY: Integer; TextFlags: DWord): Integer;


IMPLEMENTATION

TYPE
  TDrawShadowTextI = function(hdc: HDC;
    pszText: LPCWSTR;
    cch: UINT;
    const pRect: PRect;
    dwFlags: DWORD;
    crText: COLORREF;
    crShadow: COLORREF;
    ixOffset: Integer;
    iyOffset: Integer): Integer; stdcall;

VAR
  hComCtl32DLL: THandle = 0;
  DrawShadowTextI: TDrawShadowTextI;
  OldCanvasColor: TColor;
  OldBkModeColor: Integer;


// DrawShadowText as declared in ComCtl32.dll ( requires WindowsXP-Manifest! )
// function DrawShadowText_(hdc: HDC; pszText: LPCWSTR; cch: UINT; const pRect: PRect; dwFlags: DWORD; crText: COLORREF; crShadow: COLORREF; ixOffset: Integer; iyOffset: Integer): Integer; stdcall; external 'ComCtl32.dll' name 'DrawShadowText';



// Determines whether a Windows version from WinXP on is available.
function IsWindowsXPAndUp: Boolean;
begin
  Result := ((Win32MajorVersion = 5) and (Win32MinorVersion >= 1)) or (Win32MajorVersion > 5);
end;


// DrawShadowTextL (L - Low Quality)
function DrawShadowTextL(ACanvas: TCanvas; TextRect: TRect; AText: string;
  TextColor, ShadowColor: TColor; ShadowSpaceX,
  ShadowSpaceY: Integer; TextFlags: DWORD): Integer;
begin
  OldBkModeColor := SetBKMode(ACanvas.Handle, TRANSPARENT);
  OldCanvasColor := ACanvas.Font.Color;

  if UseLQShadow
  then
   begin
    inc(TextRect.Left, ShadowSpaceX);
    inc(TextRect.Top, ShadowSpaceY);
    inc(TextRect.Right, ShadowSpaceX);
    inc(TextRect.Bottom, ShadowSpaceY);

    ACanvas.Font.Color := ShadowColor;

    Result := DrawText(ACanvas.Handle, PChar(AText), length(AText), TextRect, TextFlags);

    dec(TextRect.Left, ShadowSpaceX);
    dec(TextRect.Top, ShadowSpaceY);
    dec(TextRect.Right, ShadowSpaceX);
    dec(TextRect.Bottom, ShadowSpaceY);
   end
  else
    Result := 1;

  ACanvas.Font.Color := TextColor;
  Result := Result AND DrawText(ACanvas.Handle, PChar(AText), length(AText), TextRect, TextFlags);

  ACanvas.Font.Color := OldCanvasColor;
  SetBKMode(ACanvas.Handle, OldBkModeColor);
end;


// DrawShadowText: für einfache Ausgabe
function DrawShadowText(ACanvas: TCanvas; x, y: Integer; AText: string; TextColor, ShadowColor: TColor; ShadowSpaceX, ShadowSpaceY: Integer): Integer;
VAR TextRect: TRect;
begin
  TextRect := RECT(x, y, x + ACanvas.TextWidth(AText), y + ACanvas.TextHeight(AText));

  if @DrawShadowTextI <> nil
  then Result := DrawShadowTextI(ACanvas.Handle, PWideChar(WideString(AText)), length(AText), @TextRect, 0, COLORREF(TextColor), COLORREF(ShadowColor), ShadowSpaceX, ShadowSpaceY)
  else Result := DrawShadowTextL(ACanvas, TextRect, AText, TextColor, ShadowColor, ShadowSpaceX, ShadowSpaceY, 0);
end;


// DrawShadowTextR: for formatted output (R - Text[R]ect)
function DrawShadowTextR(ACanvas: TCanvas; TextRect: TRect; x, y: Integer; AText: string; TextColor, ShadowColor: TColor; ShadowSpaceX, ShadowSpaceY: Integer; TextFlags: DWord): Integer;
begin
  if @DrawShadowTextI <> NIL
  then Result := DrawShadowTextI(ACanvas.Handle, PWideChar(WideString(AText)), length(AText), @TextRect, TextFlags, COLORREF(TextColor), COLORREF(ShadowColor), ShadowSpaceX, ShadowSpaceY)
  else Result := DrawShadowTextL(ACanvas, TextRect, AText, TextColor, ShadowColor, ShadowSpaceX, ShadowSpaceY, TextFlags);
end;



initialization
  if IsWindowsXPAndUp then
   begin
    hComCtl32DLL := LoadLibrary('ComCtl32.dll');
    @DrawShadowTextI := GetProcAddress(hComCtl32DLL, 'DrawShadowText');
   end;

finalization
  if hComCtl32DLL <> 0
  then FreeLibrary(hComCtl32DLL);

end.

如何在桌面图标上绘制像Windows XP一样的阴影文本？

4 个答案: