windows-xp - 如何像 Windows XP 一样在桌面图标上绘制带有阴影的文本？

Question

Windows XP 绘制带有漂亮阴影的图标文本，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）或根本没有阴影（如果桌面背景为黑色）。

所以有两个子任务：

1. 阴影是如何绘制的？它不是文本的简单 x,y 偏移；阴影对我来说更像是一种模糊。

2. 如何使阴影的行为方式在白色背景上变得更明显而在黑暗中变得不那么明显？

我需要 GDI（不是 GDI+）的解决方案。

Answer 1

请阅读使用 Windows GDI 的发光和阴影效果。

Answer 2

受到Chris Becke 在此线程中的回答的启发

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 alpha 混合到主 hdc，但是：将目标矩形 -1 .. 2 移动 x 并将 -1 .. 3 移动 y （即循环中的多个混合）。为了实现阴影淡化效果，相应地修改 SourceConstantAlpha 以用于外部混合（|x| > 1 或 |y| > 1）。

这是一个粗略的方法，请随意尝试细节。

我不确定这种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：在图像上写入透明文本

函数原型是这样的：procedure DrawShadowText(aCanvas: TCanvas; CONST Text: string; CONST X, Y, Opacity: Integer; TextColor, ShadowColor: TColor);
它可以使用了。

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-dl​​l-3.html

这是英文版：

{-------------------------------------------------------------------------------------------------------------
  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.