阿尔法降低后，玻璃背景上的绘图文字变得模糊

时间：2012-07-03 08:52:28

标签： delphi google-chrome windows-7 transparency gdi+

我正在对TIceTabSet（Chrome标签）组件进行多次更新。其中一项变化是增加透明度。除了文本之外，一切都很好。随着背景的alpha通道变低，文本变得越来越模糊。这是一个截图。

enter image description here

这是绘制标签的代码。其中大部分是原始的TIceTabSet代码。我只是添加了一些更改以使标签透明。对于示例屏幕截图，代码也进行了一些修改。底部的DrawText命令是将文本绘制到画布的位置。

procedure TIceTabSet.InnerDraw(Canvas: TCanvas; TabRect: TRect; Item: TIceTab);
var
  graphics : TGPGraphics;
  Pen: TGPPen;
  Brush: TGPSolidBrush;
  path, linePath: TGPGraphicsPath;
  linGrBrush: TGPLinearGradientBrush;
  font: TGPFont;
  solidBrush: TGPSolidBrush;
  rectF: TGPRectF;
  stringFormat: TGPStringFormat;
  DC: HDC;
  marginRight: integer;
  iconY, iconX: integer;
  textStart: Extended;
  startColor, EndColor, textColor, borderColor: cardinal;
  borderWidth: Integer;
  TabProperties: TIceTabProperties;
  Alpha: Byte;
begin
  DC := Canvas.Handle;

  TabProperties := GetTabProperties(Item);

  Alpha := Item.Index * 50;

  startColor := MakeGDIPColor(TabProperties.TabStyle.StartColor, Alpha);// TabProperties.TabStyle.Alpha);
  endColor := MakeGDIPColor(TabProperties.TabStyle.StopColor, Alpha); //TabProperties.TabStyle.Alpha);
  textColor := MakeGDIPColor(TabProperties.Font.Color, 255); //TabProperties.TabStyle.Alpha);
  borderColor := MakeGDIPColor(TabProperties.BorderColor, TabProperties.TabStyle.Alpha);
  borderWidth := TabProperties.BorderWidth;

  graphics := TGPGraphics.Create(DC);
  Brush := TGPSolidBrush.Create(borderColor);
  Pen:= TGPPen.Create(borderColor);
  Font := GetGDIPFont(Canvas, FTabActive.Font); //TabProperties.Font);
  try
    graphics.SetSmoothingMode(SmoothingModeHighQuality);

    pen.SetWidth(borderWidth);

    path := TGPGraphicsPath.Create();
    try
      path.AddBezier(TabRect.Left, TabRect.Bottom, TabRect.Left + FTabShape.LeftEdgeWidth / 2, TabRect.Bottom, TabRect.Left + FTabShape.LeftEdgeWidth / 2, TabRect.Top, TabRect.Left + FTabShape.LeftEdgeWidth, TabRect.Top);
      path.AddLine(TabRect.Left + FTabShape.LeftEdgeWidth, TabRect.Top, TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top);
      path.AddBezier(TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top, TabRect.Right - FTabShape.RightEdgeWidth / 2, TabRect.Top, TabRect.Right - FTabShape.RightEdgeWidth / 2, TabRect.Bottom, TabRect.Right, TabRect.Bottom);

      linePath := TGPGraphicsPath.Create;
      try
        linePath.AddPath(path, false);
        path.AddLine(TabRect.Right, TabRect.Bottom, TabRect.Left, TabRect.Bottom);

        linGrBrush := TGPLinearGradientBrush.Create(
          MakePoint(0, TabRect.Top),
          MakePoint(0, TabRect.Bottom),
          startColor,
          endColor);
        try
          graphics.DrawPath(pen, linePath);

          graphics.FillPath(linGrBrush, path);
        finally
          linGrBrush.Free;
        end;
      finally
        linePath.Free;
      end;
    finally
      path.Free;
    end;

    marginRight := 0;

    if TabDisplaysCloseButton(Item) then
    begin
      if (HighLightTabClose = Item) and
         (FTabCloseButton.ShowCircle) then
      begin
        pen.SetWidth(1);

        pen.SetColor(MakeGDIPColor(FTabCloseButton.CrossColorHotTrack, 255));
        brush.SetColor(MakeGDIPColor(FTabCloseButton.CircleColorHotTrack, 255));

        graphics.FillEllipse(brush, TabRect.Right - FTabShape.RightEdgeWidth - 7 - 2,
                                    TabRect.Top + ((TabRect.Bottom - TabRect.Top - 7) div 2) - 3,
                                    (TabRect.Right - FTabShape.RightEdgeWidth) - (TabRect.Right - FTabShape.RightEdgeWidth - 7) + 6,
                                    (TabRect.Top + ((TabRect.Bottom - TabRect.Top + 7) div 2)) - (TabRect.Top + ((TabRect.Bottom - TabRect.Top - 7) div 2)) + 6);

        graphics.DrawLine(pen, TabRect.Right - FTabShape.RightEdgeWidth - 5, TabRect.Top + ((TabRect.Bottom - TabRect.Top - 5) div 2),
                               TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top + ((TabRect.Bottom - TabRect.Top + 5) div 2));

        graphics.DrawLine(pen, TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top + ((TabRect.Bottom - TabRect.Top - 5) div 2),
                               TabRect.Right - FTabShape.RightEdgeWidth - 5, TabRect.Top + ((TabRect.Bottom - TabRect.Top + 5) div 2));
      end
      else
      begin
        pen.SetWidth(2);

        if HighlightTabClose = Item then
          pen.SetColor(MakeGDIPColor(FTabCloseButton.CrossColorHotTrack, 255))
        else
          pen.SetColor(MakeGDIPColor(FTabCloseButton.CrossColorNormal, 255));

        graphics.DrawLine(pen, TabRect.Right - FTabShape.RightEdgeWidth - 7, TabRect.Top + ((TabRect.Bottom - TabRect.Top - 7) div 2),
                               TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top + ((TabRect.Bottom - TabRect.Top + 7) div 2));

        graphics.DrawLine(pen, TabRect.Right - FTabShape.RightEdgeWidth, TabRect.Top + ((TabRect.Bottom - TabRect.Top - 7) div 2),
                               TabRect.Right - FTabShape.RightEdgeWidth - 7, TabRect.Top + ((TabRect.Bottom - TabRect.Top + 7) div 2));
      end;

      marginRight := 10;
    end;

    solidBrush:= TGPSolidBrush.Create(MakeGDIPColor(textColor, 255));

    stringFormat:= TGPStringFormat.Create;
    stringFormat.SetAlignment(StringAlignmentNear);
    stringFormat.SetLineAlignment(StringAlignmentCenter);
    stringFormat.SetTrimming(StringTrimmingEllipsisCharacter);
    stringFormat.SetFormatFlags(StringFormatFlagsNoWrap);

    SelectClipRgn(Canvas.Handle, 0);
    textStart := TabRect.Left + FTabShape.LeftEdgeWidth;
    iconX := 0;
    iconY := 0;

    if Assigned(Images) and (Item.ImageIndex <> -1) then
    begin
      iconY := TabRect.Top + ((TabRect.Bottom - TabRect.Top - Images.Height) div 2);
      iconX := Round(textStart);
      textStart := textStart + Images.Width + 4;
    end;

    rectF := MakeRect(textStart, TabRect.Top, TabRect.Right - textStart - FTabShape.RightEdgeWidth - marginRight,
      TabRect.Bottom - TabRect.Top);

    // ****** Text is drawn here *******
    if rectF.Width > 10 then
      graphics.DrawString(format('Alpha: %d', [Alpha]), -1, font, rectF, stringFormat, solidBrush);
    // *********************************

  finally
    font.Free;
    solidBrush.Free;
    Pen.Free;
    graphics.Free;
  end;

  if Assigned(Images) and
    (Item.ImageIndex <> -1) then
    Images.Draw(Canvas, iconX, iconY, Item.ImageIndex, true);
end;

您可以下载完整的来源here。请注意，这是一项正在进行中的工作。源文件完成后将提交给原作者。

更新1

将代码更改为TLama建议肯定有帮助，但它并没有完全解决问题。以下是文本现在的样子：

enter image description here

...这就是Google Chrome的外观：

enter image description here

更新2

以下是 TextRenderingHintSingleBitPerPixelGridFit 的外观。

enter image description here

我已经尝试了所有选项， TextRenderingHintAntiAlias 可以获得最佳效果。

2 个答案:

答案 0 :(得分：13)

正如Ian Boyd在他关于How to draw ClearType text on Aero glass ?的好文章中所建议的那样，当你在一张玻璃上渲染文字时，你应该使用抗锯齿。因此，要解决您的问题，请尝试以这种方式修改您的代码：

if rectF.Width > 10 then
begin
  if (GetParentForm.GlassFrame.Enabled) and (GetParentForm.GlassFrame.SheetOfGlass) then
    graphics.SetTextRenderingHint(TextRenderingHintAntiAliasGridFit);
  graphics.DrawString(Item.DisplayCaption, -1, font, rectF, stringFormat, solidBrush);
end;

要模拟您的问题，只需在Aero玻璃板上渲染文字就足够了，就像下面的代码以3种不同的方式一样：

uses
  GDIPAPI, GDIPOBJ;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Font.Color := clWhite;
  GlassFrame.SheetOfGlass := True;
  GlassFrame.Enabled := True;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  S: WideString;
  GPFont: TGPFont;
  GPGraphics: TGPGraphics;
  GPSolidBrush: TGPSolidBrush;
  GPGraphicsPath: TGPGraphicsPath;
begin
  S := 'This is a sample text rendered on the sheet of Aero glass!';
  GPFont := TGPFont.Create(Canvas.Handle, Font.Handle);
  GPSolidBrush := TGPSolidBrush.Create(MakeColor(GetRValue(Font.Color),
    GetGValue(Font.Color), GetBValue(Font.Color)));
  GPGraphicsPath := TGPGraphicsPath.Create;
  GPGraphicsPath.AddString(S, Length(S), TGPFontFamily.Create(Font.Name),
    GPFont.GetStyle, GPFont.GetSize, MakePoint(20.0, 60.0), nil);
  try
    GPGraphics := TGPGraphics.Create(Canvas.Handle);
    try
      GPGraphics.SetSmoothingMode(SmoothingModeAntiAlias);
      GPGraphics.FillPath(GPSolidBrush, GPGraphicsPath);
      GPGraphics.DrawString(S, Length(S), GPFont, MakePoint(20.0, 20.0),
        nil, GPSolidBrush);
      GPGraphics.SetTextRenderingHint(
        TextRenderingHintSingleBitPerPixelGridFit);
      GPGraphics.DrawString(S, Length(S), GPFont, MakePoint(20.0, 40.0),
        nil, GPSolidBrush);
    finally
      GPGraphics.Free;
    end;
  finally
    GPFont.Free;
    GPSolidBrush.Free;
    GPGraphicsPath.Free;
  end;
end;

结果如下图所示：

  1. 第一个文本由DrawString函数呈现，未启用文本抗锯齿功能
  2. 第二个由DrawString函数呈现，启用了文本抗锯齿，配置为TextRenderingHintSingleBitPerPixelGridFit模式
  3. 第三个由路径填充渲染，灵感来自this article，平滑模式设置为SmoothingModeAntiAlias样式

    4. enter image description here

答案 1 :(得分：5)

作为替代方案，您可以尝试使用主题api（Vista和更高版本）进行绘图。使用各种阴影/边框/发光设置，可能会提出可读文本。一些试用玻璃板：


enter image description here

代码（XE2）：

procedure TForm1.FormPaint(Sender: TObject);
var
  R: TRect;
  ThemeData: HTHEME;
  Opts: TDTTOpts;
begin
  R := Rect(10, 10, 150, 30);
  vcl.themes.DrawGlassText(Canvas.Handle, 'DrawGlassText Sample', R, 0, 3,
      clBlack, TStyleManager.SystemStyle.GetElementDetails(ttsLabel));


  OffsetRect(R, 160, 0);
  ThemeData := OpenThemeData(Handle, 'textstyle');

  Opts.dwSize := SizeOf(Opts);
  Opts.crText := ColorToRGB(clBlack);
  Opts.crShadow := $D0D0B0;
  Opts.iTextShadowType := TST_SINGLE;
  Opts.ptShadowOffset := Point(1, 1);
  Opts.fApplyOverlay := True;
  Opts.iGlowSize := 3;
  Opts.dwFlags := DTT_TEXTCOLOR or DTT_SHADOWTYPE or DTT_SHADOWCOLOR
      or DTT_SHADOWOFFSET or DTT_GLOWSIZE;
  DrawThemeTextEx(ThemeData, Canvas.Handle, TEXT_LABEL, TS_NORMAL,
      'DrawThemeTextEx Sample', -1, 0, @R, Opts);

  OffsetRect(R, 180, 0);
  Opts.crText := ColorToRGB(clBlack);
  Opts.iGlowSize := 4;
  Opts.fApplyOverlay := True;
  Opts.dwFlags := DTT_TEXTCOLOR or DTT_GLOWSIZE;
  DrawThemeTextEx(ThemeData, Canvas.Handle, TEXT_BODYTITLE, 0,
      'Another Sample', -1, 0, @R, Opts);

  CloseThemeData(ThemeData);
end;
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