Question

我注意到，在Delphi XE6（以及生成在Windows上运行的应用程序并使用本机GDI字体渲染的其他工具/语言）中，Win32 TextOut API似乎不会平滑任何大于149的字体，即，Font.Size＆gt; 149。这是一个屏幕截图，显示两个SpeedButtons，其中Font.Quality设置为fqClearType，左边的一个Font.Size设置为149，右边的一个设置Font.Size是150.这是一个点差异。高度值分别为-199和-200。这只是用Delphi组件和表单演示，也可以在TPaintBox中演示，使用Canvas.Font和调用Win32 API DrawText，或者使用纯Win32 API应用程序创建一个窗口，并使用DrawText绘制到设备上下文。

这里明确显示了GDI的限制;请注意，ClearType在size = 149时看起来平庸（水平消除锯齿但没有垂直），ClearType在150处完全关闭：

enter image description here

我的问题是，有没有办法绕过Win32 API GDI中的这个限制，使用Windows 7及更高版本上提供的一些原始Win32函数来绘制文本并始终使用反别名？我假设逻辑字体处理正在VCL内部正确完成，因为在C＃应用程序中使用相同的限制（使用WinForms，它在GDI上运行），就像我在Delphi中尝试这样时一样。

我想在GDI画布上绘制一个字体大小超过149的消除锯齿的字符，使用Clear Type或经典的Anti-Aliasing。我该怎么做？

请注意，我已经将Font.Quality显式设置为AntiAliased和ClearType模式，并且Win32 GDI api调用忽略了某些大小的逻辑字体属性，显然是通过设计。某些应用程序（如Microsoft Word）显然具有字体呈现功能，可以绘制155磅或更大的字体，在这种情况下仍然是抗锯齿。

更新：我回答了我自己的问题，显示了DirectWrite + GDI互操作是多么容易。在Windows 7和Windows 8以及之后，DirectWrite实际上提供了水平和垂直抗锯齿，我相信这是高质量的屏幕字体渲染模式，就像MS Word 2013这样的应用程序正在使用。我相信有人可以轻松回答我的问题，显示一个GDI +样本，这也符合我的要求（因为GDI +包含在Windows 7和8中）。

Answer 1

我发现与GDI互操作优于GDI +的工作方法是使用DirectWrite，但这仅适用于Windows 7和8，我在此提供的示例代码具有简单的GDI回退模式（简单的GDI，没有抗锯齿），涵盖XP和Vista，至少提供优雅的降级;它仍然使用GDI在Win7之前的操作系统上绘制文本。

最初的演示应用程序在这里，但它使用的是TForm，我改为TWinControl，它没有GDI后备，只是一个例外。

http://cc.embarcadero.com/item/27491

编写上述演示的Pawel Glowacki的讨论/博客文章在这里：

http://blogs.embarcadero.com/pawelglowacki/2009/12/14/38872

此处显示了一个代码片段，其中包含来自Pawel演示的经过修改的D2DUtils.pas，并添加了GDI后备功能（而不是用例外处理）。

uses
  Windows,
  Messages,
  SysUtils,
  Variants,
  Classes,
  Graphics,
  Controls,
  Forms,
  Dialogs,
  Winapi.D2D1,
  Vcl.Direct2D;


type
   TCanvasD2D = class(TWinControl) // a base class, using TWinControl instead of TForm.
   private
      FInitFlag: Boolean;
      FGDIMode: Boolean; { Fallback }
      FD2DCanvas: TDirect2DCanvas; { Used When D2D is available and GDIMode=False }
      FGDICanvas: TCanvas; { Fallback canvas, used when FGDIMode=True }
      procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
   protected
      procedure Resize; override;

      procedure DoPaint(AHDC: HDC); virtual;

      procedure CreateD2DResources; virtual;

      procedure PaintD2D; virtual;
      procedure PaintGDI; virtual;

      function RenderTarget: ID2D1RenderTarget; // convenience function used during D2D Paints.

      procedure PaintWindow(DC: HDC); override;

   public
      constructor Create(AOwner: TComponent); override;
      destructor Destroy; override;

      procedure Init;
      property D2DCanvas: TDirect2DCanvas read FD2DCanvas;
      property GDICanvas: TCanvas read FGDICanvas;

      property GDIMode: Boolean read FGDIMode write FGDIMode;
      { Set to true to force GDI fallback, will automatically set true if D2D is not available, also }
   end;


TCanvasD2DSample = class(TCanvasD2D) // subclass of TCanvasD2D that is a primitive "TLabel"
    private
    FFontBrush: ID2D1SolidColorBrush;// Brush generated from current value of FFontColor
    FBackgroundColor:TColor; // clWhite
    FFontColor:TColor; //clBlack;
    FTextFormat: IDWriteTextFormat;
    FFontName: string;
    FFontSize: Integer;  { Units?}
    FDisplayText: String;
    FLocale: String;


    procedure SetFontName(const Value: String);
    procedure SetFontSize(const Value: Integer);
    procedure SetDisplayText(const Value: String);

  protected
    procedure PaintD2D; override;
    procedure PaintGDI; override;
    procedure CreateD2DResources; override;

    function FontSizeToDip(FontSize:Integer ):Double;

  public
    constructor Create(AOwner: TComponent); override;

    property TextFormat:IDWriteTextFormat read FTextFormat;
    property FontSize:Integer read FFontSize write SetFontSize;
    property FontName:String read FFontName write SetFontName;
    property DisplayText: String read FDisplayText write SetDisplayText;

    property BackgroundColor:TColor read FBackgroundColor write FBackgroundColor;
    property FontColor:TColor read FFontColor write FFontColor; //clBlack;


    property Locale: String read FLocale write FLocale; // string like 'en-us'

  end;

implementation

constructor TCanvasD2D.Create(AOwner: TComponent);
begin
   inherited;

end;

destructor TCanvasD2D.Destroy;
begin
   FD2DCanvas.Free;
   FD2DCanvas := nil;
   FGDICanvas.Free;
   FGDICanvas := nil;

   inherited;
end;

procedure TCanvasD2D.Init;
begin
   if not FInitFlag then
   begin
      FInitFlag := True;

      if (not FGDIMode) and (TDirect2DCanvas.Supported) then
      begin
         if Assigned(FD2DCanvas) then
            FD2DCanvas.Free;
         FD2DCanvas := TDirect2DCanvas.Create(Handle);
         CreateD2DResources;
      end
      else
      begin
         FGDIMode := True;
         if Assigned(FGDICanvas) then
            FGDICanvas.Free;
         FGDICanvas := TCanvas.Create;
         FGDICanvas.Handle := GetDC(Self.Handle);
      end;
   end;
end;

procedure TCanvasD2D.CreateD2DResources;
begin
   // create Direct2D resources in descendant class
end;

function TCanvasD2D.RenderTarget: ID2D1RenderTarget;
begin
   Result := D2DCanvas.RenderTarget;
end;

procedure TCanvasD2D.Resize;
var
   HwndTarget: ID2D1HwndRenderTarget;
   ASize: TD2D1SizeU;
begin
   inherited;

   if Assigned(D2DCanvas) then
      if Supports(RenderTarget, ID2D1HwndRenderTarget, HwndTarget) then
      begin
         ASize := D2D1SizeU(ClientWidth, ClientHeight);
         HwndTarget.Resize(ASize);
      end;

   Invalidate;
end;

procedure TCanvasD2D.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
   if (not FGDIMode) then
      // avoid flicker as described here:
      // http://chrisbensen.blogspot.com/2009/09/touch-demo-part-i.html
      Message.Result := 1
   else
      inherited;
end;

procedure TCanvasD2D.DoPaint(AHDC: HDC);
begin
   Init;
   if FGDIMode then
   begin
      FGDICanvas.Handle := AHDC;
      PaintGDI;
   end
   else
   begin
      D2DCanvas.BeginDraw;
      try
         PaintD2D;
      finally
         D2DCanvas.EndDraw;
      end;
   end;
end;

procedure TCanvasD2D.PaintD2D;
begin
   // implement painting code in descendant class
end;

procedure TCanvasD2D.PaintGDI;
begin
   // implement in descendant.
end;

procedure TCanvasD2D.PaintWindow(DC: HDC);
begin
   DoPaint(DC);
   inherited;

end;




{ Custom Control Subclass }
procedure TCanvasD2DSample.CreateD2DResources;

begin
  inherited;

  D2DCanvas.RenderTarget.CreateSolidColorBrush(
    D2D1ColorF(FFontColor, 1),
    nil,
    FFontBrush
    );

  DWriteFactory.CreateTextFormat(
    PWideChar(FontName),
    nil,
    DWRITE_FONT_WEIGHT_REGULAR,
    DWRITE_FONT_STYLE_NORMAL,
    DWRITE_FONT_STRETCH_NORMAL,
    FontSizeToDip( FontSize),
    PWideChar(FLocale),
    FTextFormat
   );

   FTextFormat.SetTextAlignment(DWRITE_TEXT_ALIGNMENT_CENTER);
   FTextFormat.SetParagraphAlignment(DWRITE_PARAGRAPH_ALIGNMENT_CENTER);
end;



function TCanvasD2DSample.FontSizeToDip(FontSize: Integer): Double;
begin
   result := FontSize * (96.0 / 72.0); { TODO: 96.0 should not be hard coded? }
end;

procedure TCanvasD2DSample.PaintD2D;
var
  aRect: TD2D1RectF;
//  ASize:D2D_SIZE_F;
begin

  // fill with white color the whole window
  RenderTarget.Clear(D2D1ColorF(FBackgroundColor));



  RenderTarget.DrawText(
    PWideChar(FDisplayText),
    Length(FDisplayText),
    FTextFormat,
    D2D1RectF(0, 0, ClientWidth, ClientHeight),
    FFontBrush
    );

  //  RenderTarget.GetSize(ASize);
end;

procedure TCanvasD2DSample.PaintGDI;
begin
  { FALLBACK PAINT MODE}
  GDICanvas.Lock;
  GDICanvas.Font.Name := FFontName;
  GDICanvas.Font.Size := FFontSize;
  GDICanvas.Font.Color := FFontColor;
  GDICanvas.Brush.Style := bsSolid;
  GDICanvas.Brush.Color := FBackgroundColor;
  GDICanvas.Rectangle(Self.ClientRect);


  GDICanvas.TextOut(0,0, FDisplayText);
GDICanvas.Unlock;
end;

procedure TCanvasD2DSample.SetDisplayText(const Value: String);
begin
   if Value<>FDisplayText then
   begin
    FDisplayText := Value;
    Invalidate;
   end;
end;

procedure TCanvasD2DSample.SetFontName(const Value: String);
begin
  FFontName := Value;
end;

procedure TCanvasD2DSample.SetFontSize(const Value: Integer);
begin
  FFontSize := Value;
end;

我可以生成大于149的抗锯齿字体吗？

1 个答案: